https://github.com/spavloff created 
https://github.com/llvm/llvm-project/pull/199557

Previously exception handling behavior was uses as an indicator of sNaN 
support. With introducing a special function attribute `signaling_nans` the 
checks for sNaN support must be changed to use the function attribute rather 
than the exception behavior.

>From cef112e8c0c16dc1af3b161f2b67d5b36591feb5 Mon Sep 17 00:00:00 2001
From: Serge Pavlov <[email protected]>
Date: Thu, 21 May 2026 00:59:28 +0700
Subject: [PATCH] Update transformations sensitive to signaling NaNs

Previously exception handling behavior was uses as an indicator of sNaN
support. With introducing a special function attribute `signaling_nans`
the checks for sNaN support must be changed to use the function
attribute rather than the exception behavior.
---
 llvm/include/llvm/Analysis/SimplifyQuery.h    |   8 +
 llvm/include/llvm/IR/FPEnv.h                  |   6 -
 llvm/lib/Analysis/InstructionSimplify.cpp     |  38 +--
 .../Transforms/InstSimplify/fdiv-strictfp.ll  |  28 ++
 .../floating-point-arithmetic-strictfp.ll     |  28 ++
 .../Transforms/InstSimplify/strictfp-fadd.ll  | 133 ++++++++-
 .../Transforms/InstSimplify/strictfp-fsub.ll  | 252 ++++++++++++++++--
 7 files changed, 436 insertions(+), 57 deletions(-)

diff --git a/llvm/include/llvm/Analysis/SimplifyQuery.h 
b/llvm/include/llvm/Analysis/SimplifyQuery.h
index b81b1dae27471..9a605ea9ed3a4 100644
--- a/llvm/include/llvm/Analysis/SimplifyQuery.h
+++ b/llvm/include/llvm/Analysis/SimplifyQuery.h
@@ -126,6 +126,14 @@ struct SimplifyQuery {
   /// Otherwise always return false.
   LLVM_ABI bool isUndefValue(Value *V) const;
 
+  bool expectsSignalingNaNs() const {
+    if (CxtI)
+      if (const BasicBlock *BB = CxtI->getParent())
+        if (const Function *F = BB->getParent())
+          return F->hasFnAttribute(Attribute::SignalingNans);
+    return false;
+  }
+
   SimplifyQuery getWithoutDomCondCache() const {
     SimplifyQuery Copy(*this);
     Copy.DC = nullptr;
diff --git a/llvm/include/llvm/IR/FPEnv.h b/llvm/include/llvm/IR/FPEnv.h
index 38395b15c8c09..a3b7d1c26972d 100644
--- a/llvm/include/llvm/IR/FPEnv.h
+++ b/llvm/include/llvm/IR/FPEnv.h
@@ -80,11 +80,5 @@ LLVM_ABI Intrinsic::ID getConstrainedIntrinsicID(const 
Instruction &Instr);
 inline bool canRoundingModeBe(RoundingMode RM, RoundingMode QRM) {
   return RM == QRM || RM == RoundingMode::Dynamic;
 }
-
-/// Returns true if the possibility of a signaling NaN can be safely
-/// ignored.
-inline bool canIgnoreSNaN(fp::ExceptionBehavior EB, FastMathFlags FMF) {
-  return (EB == fp::ebIgnore || FMF.noNaNs());
-}
 }
 #endif
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp 
b/llvm/lib/Analysis/InstructionSimplify.cpp
index 4780c18bec421..956b2447d53ed 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -94,6 +94,10 @@ static Constant *getFalse(Type *Ty) { return 
ConstantInt::getFalse(Ty); }
 /// with every element true.
 static Constant *getTrue(Type *Ty) { return ConstantInt::getTrue(Ty); }
 
+inline bool canIgnoreSNaN(const SimplifyQuery &Q, FastMathFlags FMF) {
+  return !Q.expectsSignalingNaNs() || FMF.noNaNs();
+}
+
 /// isSameCompare - Is V equivalent to the comparison "LHS Pred RHS"?
 static bool isSameCompare(Value *V, CmpPredicate Pred, Value *LHS, Value *RHS) 
{
   CmpInst *Cmp = dyn_cast<CmpInst>(V);
@@ -5935,14 +5939,14 @@ simplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags 
FMF,
   // not simplify to Op0:
   // fadd SNaN, -0.0 --> QNaN
   // fadd +0.0, -0.0 --> -0.0 (but only with round toward negative)
-  if (canIgnoreSNaN(ExBehavior, FMF) &&
+  if (canIgnoreSNaN(Q, FMF) &&
       (!canRoundingModeBe(Rounding, RoundingMode::TowardNegative) ||
        FMF.noSignedZeros()))
     if (match(Op1, m_NegZeroFP()))
       return Op0;
 
   // fadd X, 0 ==> X, when we know X is not -0
-  if (canIgnoreSNaN(ExBehavior, FMF))
+  if (canIgnoreSNaN(Q, FMF))
     if (match(Op1, m_PosZeroFP()) &&
         (FMF.noSignedZeros() || cannotBeNegativeZero(Op0, Q)))
       return Op0;
@@ -5997,14 +6001,14 @@ simplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags 
FMF,
     return C;
 
   // fsub X, +0 ==> X
-  if (canIgnoreSNaN(ExBehavior, FMF) &&
+  if (canIgnoreSNaN(Q, FMF) &&
       (!canRoundingModeBe(Rounding, RoundingMode::TowardNegative) ||
        FMF.noSignedZeros()))
     if (match(Op1, m_PosZeroFP()))
       return Op0;
 
   // fsub X, -0 ==> X, when we know X is not -0
-  if (canIgnoreSNaN(ExBehavior, FMF))
+  if (canIgnoreSNaN(Q, FMF))
     if (match(Op1, m_NegZeroFP()) &&
         (FMF.noSignedZeros() || cannotBeNegativeZero(Op0, Q)))
       return Op0;
@@ -6012,13 +6016,13 @@ simplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags 
FMF,
   // fsub -0.0, (fsub -0.0, X) ==> X
   // fsub -0.0, (fneg X) ==> X
   Value *X;
-  if (canIgnoreSNaN(ExBehavior, FMF))
+  if (canIgnoreSNaN(Q, FMF))
     if (match(Op0, m_NegZeroFP()) && match(Op1, m_FNeg(m_Value(X))))
       return X;
 
   // fsub 0.0, (fsub 0.0, X) ==> X if signed zeros are ignored.
   // fsub 0.0, (fneg X) ==> X if signed zeros are ignored.
-  if (canIgnoreSNaN(ExBehavior, FMF))
+  if (canIgnoreSNaN(Q, FMF))
     if (FMF.noSignedZeros() && match(Op0, m_AnyZeroFP()) &&
         (match(Op1, m_FSub(m_AnyZeroFP(), m_Value(X))) ||
          match(Op1, m_FNeg(m_Value(X)))))
@@ -6058,16 +6062,18 @@ static Value *simplifyFMAFMul(Value *Op0, Value *Op1, 
FastMathFlags FMF,
   if (Constant *C = simplifyFPOp({Op0, Op1}, FMF, Q, ExBehavior, Rounding))
     return C;
 
-  if (!isDefaultFPEnvironment(ExBehavior, Rounding))
-    return nullptr;
-
   // Canonicalize special constants as operand 1.
   if (match(Op0, m_FPOne()) || match(Op0, m_AnyZeroFP()))
     std::swap(Op0, Op1);
 
   // X * 1.0 --> X
-  if (match(Op1, m_FPOne()))
-    return Op0;
+  // except: SNaN * 1.0 -> QNaN
+  if (canIgnoreSNaN(Q, FMF))
+    if (match(Op1, m_FPOne()))
+      return Op0;
+
+  if (!isDefaultFPEnvironment(ExBehavior, Rounding))
+    return nullptr;
 
   if (match(Op1, m_AnyZeroFP())) {
     // X * 0.0 --> 0.0 (with nnan and nsz)
@@ -6158,13 +6164,15 @@ simplifyFDivInst(Value *Op0, Value *Op1, FastMathFlags 
FMF,
   if (Constant *C = simplifyFPOp({Op0, Op1}, FMF, Q, ExBehavior, Rounding))
     return C;
 
+  // X / 1.0 -> X
+  // except: SNaN / 1.0 -> QNaN
+  if (canIgnoreSNaN(Q, FMF))
+    if (match(Op1, m_FPOne()))
+      return Op0;
+
   if (!isDefaultFPEnvironment(ExBehavior, Rounding))
     return nullptr;
 
-  // X / 1.0 -> X
-  if (match(Op1, m_FPOne()))
-    return Op0;
-
   // 0 / X -> 0
   // Requires that NaNs are off (X could be zero) and signed zeroes are
   // ignored (X could be positive or negative, so the output sign is unknown).
diff --git a/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll 
b/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
index a0fd8fe74bc67..de753adce84c2 100644
--- a/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
+++ b/llvm/test/Transforms/InstSimplify/fdiv-strictfp.ll
@@ -84,6 +84,33 @@ define <2 x float> @fmul_fdiv_common_operand_commute_vec(<2 
x float> %x, <2 x fl
   ret <2 x float> %d
 }
 
+define float @fmul_fdiv_unity(float %x) #0 {
+; CHECK-LABEL: @fmul_fdiv_unity(
+; CHECK-NEXT:    ret float [[X:%.*]]
+;
+  %fdiv = call float @llvm.experimental.constrained.fdiv.f32(float %x, float 
1.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %fdiv
+}
+
+define float @fmul_fdiv_unity_signaling(float %x) #1 {
+; CHECK-LABEL: @fmul_fdiv_unity_signaling(
+; CHECK-NEXT:    [[FDIV:%.*]] = call float 
@llvm.experimental.constrained.fdiv.f32(float [[X:%.*]], float 1.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[FDIV]]
+;
+  %fdiv = call float @llvm.experimental.constrained.fdiv.f32(float %x, float 
1.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %fdiv
+}
+
+define float @fmul_fdiv_unity_signaling_nnan(float %x) #1 {
+; CHECK-LABEL: @fmul_fdiv_unity_signaling_nnan(
+; CHECK-NEXT:    ret float [[X:%.*]]
+;
+  %fdiv = call nnan float @llvm.experimental.constrained.fdiv.f32(float %x, 
float 1.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %fdiv
+}
+
+
+
 declare double @llvm.experimental.constrained.fmul.f64(double, double, 
metadata, metadata) #0
 declare <2 x float> @llvm.experimental.constrained.fmul.v2f32(<2 x float>, <2 
x float>, metadata, metadata) #0
 
@@ -94,4 +121,5 @@ declare <2 x float> 
@llvm.experimental.constrained.fdiv.v2f32(<2 x float>, <2 x
 declare float @llvm.experimental.constrained.frem.f32(float, float, metadata, 
metadata) #0
 
 attributes #0 = { strictfp }
+attributes #1 = { signaling_nans strictfp }
 
diff --git 
a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic-strictfp.ll 
b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic-strictfp.ll
index 9a078a8f569da..e8082906dfce4 100644
--- a/llvm/test/Transforms/InstSimplify/floating-point-arithmetic-strictfp.ll
+++ b/llvm/test/Transforms/InstSimplify/floating-point-arithmetic-strictfp.ll
@@ -514,6 +514,33 @@ define float @maxnum_with_pos_one_op(float %a) #0 {
   ret float %fabs
 }
 
+define float @fmul_unity(float %x) #0 {
+; CHECK-LABEL: @fmul_unity(
+; CHECK-NEXT:    [[FMUL:%.*]] = call float 
@llvm.experimental.constrained.fmul.f32(float [[X:%.*]], float 1.000000e+00, 
metadata !"round.dynamic", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[X]]
+;
+  %fmul = call float @llvm.experimental.constrained.fmul.f32(float %x, float 
1.0, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  ret float %fmul
+}
+
+define float @fmul_unity_signaling(float %x) #1 {
+; CHECK-LABEL: @fmul_unity_signaling(
+; CHECK-NEXT:    [[FMUL:%.*]] = call float 
@llvm.experimental.constrained.fmul.f32(float [[X:%.*]], float 1.000000e+00, 
metadata !"round.dynamic", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[FMUL]]
+;
+  %fmul = call float @llvm.experimental.constrained.fmul.f32(float %x, float 
1.0, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  ret float %fmul
+}
+
+define float @fmul_unity_signaling_nnan(float %x) #1 {
+; CHECK-LABEL: @fmul_unity_signaling_nnan(
+; CHECK-NEXT:    [[FMUL:%.*]] = call nnan float 
@llvm.experimental.constrained.fmul.f32(float [[X:%.*]], float 1.000000e+00, 
metadata !"round.dynamic", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[X]]
+;
+  %fmul = call nnan float @llvm.experimental.constrained.fmul.f32(float %x, 
float 1.0, metadata !"round.dynamic", metadata !"fpexcept.strict")
+  ret float %fmul
+}
+
 declare float @llvm.fabs.f32(float)
 declare <2 x float> @llvm.fabs.v2f32(<2 x float>)
 
@@ -532,3 +559,4 @@ declare float 
@llvm.experimental.constrained.maxnum.f32(float, float, metadata)
 declare float @llvm.experimental.constrained.sqrt.f32(float, metadata, 
metadata)
 
 attributes #0 = { strictfp }
+attributes #1 = { signaling_nans strictfp }
diff --git a/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll 
b/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
index bfc7c038322d4..2c3299eb12599 100644
--- a/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
+++ b/llvm/test/Transforms/InstSimplify/strictfp-fadd.ll
@@ -17,6 +17,15 @@ define float @fadd_x_n0_defaultenv(float %a) #0 {
   ret float %ret
 }
 
+define float @fadd_x_n0_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fadd_x_n0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float [[A1:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore") #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call float @llvm.experimental.constrained.fadd.f32(float %a, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore") #0
+  ret float %ret
+}
+
 define <2 x float> @fadd_vec_x_n0_defaultenv(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fadd_vec_x_n0_defaultenv(
 ; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
@@ -25,10 +34,18 @@ define <2 x float> @fadd_vec_x_n0_defaultenv(<2 x float> 
%a) #0 {
   ret <2 x float> %ret
 }
 
+define <2 x float> @fadd_vec_x_n0_defaultenv_signaling(<2 x float> %a) #1 {
+; CHECK-LABEL: @fadd_vec_x_n0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A1:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %ret = call <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float><float -0.0, float -0.0>, metadata !"round.tonearest", 
metadata !"fpexcept.ignore") #0
+  ret <2 x float> %ret
+}
+
 define float @fadd_x_n0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fadd_x_n0_ebmaytrap(
-; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap") #[[ATTR0:[0-9]+]]
-; CHECK-NEXT:    ret float [[RET]]
+; CHECK-NEXT:    ret float [[RET:%.*]]
 ;
   %ret = call float @llvm.experimental.constrained.fadd.f32(float %a, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap") #0
   ret float %ret
@@ -36,8 +53,7 @@ define float @fadd_x_n0_ebmaytrap(float %a) #0 {
 
 define <2 x float> @fadd_vec_x_n0_ebmaytrap(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fadd_vec_x_n0_ebmaytrap(
-; CHECK-NEXT:    [[RET:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.maytrap") #[[ATTR0]]
-; CHECK-NEXT:    ret <2 x float> [[RET]]
+; CHECK-NEXT:    ret <2 x float> [[RET:%.*]]
 ;
   %ret = call <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float><float -0.0, float -0.0>, metadata !"round.tonearest", 
metadata !"fpexcept.maytrap") #0
   ret <2 x float> %ret
@@ -45,7 +61,7 @@ define <2 x float> @fadd_vec_x_n0_ebmaytrap(<2 x float> %a) 
#0 {
 
 define float @fadd_x_n0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fadd_x_n0_ebstrict(
-; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
+; CHECK-NEXT:    [[RET1:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float [[RET:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %ret = call float @llvm.experimental.constrained.fadd.f32(float %a, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
@@ -54,7 +70,7 @@ define float @fadd_x_n0_ebstrict(float %a) #0 {
 
 define <2 x float> @fadd_vec_x_n0_ebstrict(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fadd_vec_x_n0_ebstrict(
-; CHECK-NEXT:    [[RET:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.strict") #[[ATTR0]]
+; CHECK-NEXT:    [[RET1:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[RET:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret <2 x float> [[RET]]
 ;
   %ret = call <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float><float -0.0, float -0.0>, metadata !"round.tonearest", 
metadata !"fpexcept.strict") #0
@@ -107,6 +123,15 @@ define float @fadd_x_n0_towardzero(float %a) #0 {
   ret float %ret
 }
 
+define float @fadd_x_n0_towardzero_signaling(float %a) #1 {
+; CHECK-LABEL: @fadd_x_n0_towardzero_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float [[A1:%.*]], float -0.000000e+00, 
metadata !"round.towardzero", metadata !"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call float @llvm.experimental.constrained.fadd.f32(float %a, float 
-0.0, metadata !"round.towardzero", metadata !"fpexcept.ignore") #0
+  ret float %ret
+}
+
 ; The rounding mode here needs to not be { tonearest, downward, dynamic }.
 ; Test one of the remaining rounding modes and the rest will be fine.
 define <2 x float> @fadd_vec_x_n0_towardzero(<2 x float> %a) #0 {
@@ -117,6 +142,15 @@ define <2 x float> @fadd_vec_x_n0_towardzero(<2 x float> 
%a) #0 {
   ret <2 x float> %ret
 }
 
+define <2 x float> @fadd_vec_x_n0_towardzero_signaling(<2 x float> %a) #1 {
+; CHECK-LABEL: @fadd_vec_x_n0_towardzero_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A1:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.towardzero", metadata 
!"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %ret = call <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float><float -0.0, float -0.0>, metadata !"round.towardzero", 
metadata !"fpexcept.ignore") #0
+  ret <2 x float> %ret
+}
+
 define float @fadd_nnan_x_n0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fadd_nnan_x_n0_ebmaytrap(
 ; CHECK-NEXT:    ret float [[A:%.*]]
@@ -154,7 +188,7 @@ define <2 x float> @fadd_vec_nnan_x_n0_ebstrict(<2 x float> 
%a) #0 {
 ; Test with a fast math flag set but that flag is not "nnan".
 define float @fadd_ninf_x_n0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fadd_ninf_x_n0_ebstrict(
-; CHECK-NEXT:    [[RET:%.*]] = call ninf float 
@llvm.experimental.constrained.fadd.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
+; CHECK-NEXT:    [[RET1:%.*]] = call ninf float 
@llvm.experimental.constrained.fadd.f32(float [[RET:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %ret = call ninf float @llvm.experimental.constrained.fadd.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
@@ -164,7 +198,7 @@ define float @fadd_ninf_x_n0_ebstrict(float %a) #0 {
 ; Test with a fast math flag set but that flag is not "nnan".
 define <2 x float> @fadd_vec_ninf_x_n0_ebstrict(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fadd_vec_ninf_x_n0_ebstrict(
-; CHECK-NEXT:    [[RET:%.*]] = call ninf <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.strict") #[[ATTR0]]
+; CHECK-NEXT:    [[RET1:%.*]] = call ninf <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[RET:%.*]], <2 x float> 
splat (float -0.000000e+00), metadata !"round.tonearest", metadata 
!"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret <2 x float> [[RET]]
 ;
   %ret = call ninf <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float><float -0.0, float -0.0>, metadata !"round.tonearest", 
metadata !"fpexcept.strict") #0
@@ -179,6 +213,15 @@ define float @fadd_n0_x_defaultenv(float %a) #0 {
   ret float %ret
 }
 
+define float @fadd_n0_x_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fadd_n0_x_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fadd.f32(float -0.000000e+00, float [[A1:%.*]], 
metadata !"round.tonearest", metadata !"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call float @llvm.experimental.constrained.fadd.f32(float -0.0, float 
%a, metadata !"round.tonearest", metadata !"fpexcept.ignore") #0
+  ret float %ret
+}
+
 define <2 x float> @fadd_vec_n0_x_defaultenv(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fadd_vec_n0_x_defaultenv(
 ; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
@@ -187,6 +230,15 @@ define <2 x float> @fadd_vec_n0_x_defaultenv(<2 x float> 
%a) #0 {
   ret <2 x float> %ret
 }
 
+define <2 x float> @fadd_vec_n0_x_defaultenv_signaling(<2 x float> %a) #1 {
+; CHECK-LABEL: @fadd_vec_n0_x_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> splat (float 
-0.000000e+00), <2 x float> [[A1:%.*]], metadata !"round.tonearest", metadata 
!"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %ret = call <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float><float -0.0, float -0.0>, <2 x float> %a, metadata !"round.tonearest", 
metadata !"fpexcept.ignore") #0
+  ret <2 x float> %ret
+}
+
 ; TODO: Canonicalize the order of the arguments. Then this will fire.
 define float @fadd_n0_x_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fadd_n0_x_ebmaytrap(
@@ -219,6 +271,15 @@ define float @fold_fadd_nsz_x_0_defaultenv(float %a) #0 {
   ret float %add
 }
 
+define float @fold_fadd_nsz_x_0_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fadd_nsz_x_0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %add = call nsz float @llvm.experimental.constrained.fadd.f32(float %a, 
float 0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore") #0
+  ret float %add
+}
+
 define <2 x float> @fold_fadd_vec_nsz_x_0_defaultenv(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_defaultenv(
 ; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
@@ -227,6 +288,15 @@ define <2 x float> @fold_fadd_vec_nsz_x_0_defaultenv(<2 x 
float> %a) #0 {
   ret <2 x float> %add
 }
 
+define <2 x float> @fold_fadd_vec_nsz_x_0_defaultenv_signaling(<2 x float> %a) 
#1 {
+; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A1:%.*]], <2 x float> 
zeroinitializer, metadata !"round.tonearest", metadata !"fpexcept.ignore") 
#[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %add = call nsz <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float> zeroinitializer, metadata !"round.tonearest", metadata 
!"fpexcept.ignore") #0
+  ret <2 x float> %add
+}
+
 define float @fold_fadd_nsz_x_0_neginf(float %a) #0 {
 ; CHECK-LABEL: @fold_fadd_nsz_x_0_neginf(
 ; CHECK-NEXT:    ret float [[A:%.*]]
@@ -235,6 +305,15 @@ define float @fold_fadd_nsz_x_0_neginf(float %a) #0 {
   ret float %add
 }
 
+define float @fold_fadd_nsz_x_0_neginf_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fadd_nsz_x_0_neginf_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.downward", metadata !"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %add = call nsz float @llvm.experimental.constrained.fadd.f32(float %a, 
float 0.0, metadata !"round.downward", metadata !"fpexcept.ignore") #0
+  ret float %add
+}
+
 define <2 x float> @fold_fadd_vec_nsz_x_0_neginf(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_neginf(
 ; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
@@ -243,10 +322,18 @@ define <2 x float> @fold_fadd_vec_nsz_x_0_neginf(<2 x 
float> %a) #0 {
   ret <2 x float> %add
 }
 
+define <2 x float> @fold_fadd_vec_nsz_x_0_neginf_signaling(<2 x float> %a) #1 {
+; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_neginf_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A1:%.*]], <2 x float> 
zeroinitializer, metadata !"round.downward", metadata !"fpexcept.ignore") 
#[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %add = call nsz <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float> zeroinitializer, metadata !"round.downward", metadata 
!"fpexcept.ignore") #0
+  ret <2 x float> %add
+}
+
 define float @fold_fadd_nsz_x_0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fold_fadd_nsz_x_0_ebmaytrap(
-; CHECK-NEXT:    [[ADD:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap") #[[ATTR0]]
-; CHECK-NEXT:    ret float [[ADD]]
+; CHECK-NEXT:    ret float [[ADD:%.*]]
 ;
   %add = call nsz float @llvm.experimental.constrained.fadd.f32(float %a, 
float 0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap") #0
   ret float %add
@@ -254,8 +341,7 @@ define float @fold_fadd_nsz_x_0_ebmaytrap(float %a) #0 {
 
 define <2 x float> @fold_fadd_vec_nsz_x_0_ebmaytrap(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_ebmaytrap(
-; CHECK-NEXT:    [[ADD:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A:%.*]], <2 x float> 
zeroinitializer, metadata !"round.tonearest", metadata !"fpexcept.maytrap") 
#[[ATTR0]]
-; CHECK-NEXT:    ret <2 x float> [[ADD]]
+; CHECK-NEXT:    ret <2 x float> [[ADD:%.*]]
 ;
   %add = call nsz <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float> zeroinitializer, metadata !"round.tonearest", metadata 
!"fpexcept.maytrap") #0
   ret <2 x float> %add
@@ -279,7 +365,7 @@ define <2 x float> @fold_fadd_vec_nnan_nsz_x_0_ebmaytrap(<2 
x float> %a) #0 {
 
 define float @fold_fadd_nsz_x_0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fold_fadd_nsz_x_0_ebstrict(
-; CHECK-NEXT:    [[ADD:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
+; CHECK-NEXT:    [[ADD1:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float [[ADD:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict") #[[ATTR0]]
 ; CHECK-NEXT:    ret float [[ADD]]
 ;
   %add = call nsz float @llvm.experimental.constrained.fadd.f32(float %a, 
float 0.0, metadata !"round.tonearest", metadata !"fpexcept.strict") #0
@@ -288,7 +374,7 @@ define float @fold_fadd_nsz_x_0_ebstrict(float %a) #0 {
 
 define <2 x float> @fold_fadd_vec_nsz_x_0_ebstrict(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fold_fadd_vec_nsz_x_0_ebstrict(
-; CHECK-NEXT:    [[ADD:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[A:%.*]], <2 x float> 
zeroinitializer, metadata !"round.tonearest", metadata !"fpexcept.strict") 
#[[ATTR0]]
+; CHECK-NEXT:    [[ADD1:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> [[ADD:%.*]], <2 x float> 
zeroinitializer, metadata !"round.tonearest", metadata !"fpexcept.strict") 
#[[ATTR0]]
 ; CHECK-NEXT:    ret <2 x float> [[ADD]]
 ;
   %add = call nsz <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> %a, <2 x float> zeroinitializer, metadata !"round.tonearest", metadata 
!"fpexcept.strict") #0
@@ -321,6 +407,15 @@ define float @fold_fadd_nsz_0_x_defaultenv(float %a) #0 {
   ret float %add
 }
 
+define float @fold_fadd_nsz_0_x_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fadd_nsz_0_x_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fadd.f32(float 0.000000e+00, float [[A1:%.*]], 
metadata !"round.tonearest", metadata !"fpexcept.ignore") #[[ATTR0]]
+; CHECK-NEXT:    ret float [[A]]
+;
+  %add = call nsz float @llvm.experimental.constrained.fadd.f32(float 0.0, 
float %a, metadata !"round.tonearest", metadata !"fpexcept.ignore") #0
+  ret float %add
+}
+
 define <2 x float> @fold_fadd_vec_nsz_0_x_defaultenv(<2 x float> %a) #0 {
 ; CHECK-LABEL: @fold_fadd_vec_nsz_0_x_defaultenv(
 ; CHECK-NEXT:    ret <2 x float> [[A:%.*]]
@@ -329,6 +424,15 @@ define <2 x float> @fold_fadd_vec_nsz_0_x_defaultenv(<2 x 
float> %a) #0 {
   ret <2 x float> %add
 }
 
+define <2 x float> @fold_fadd_vec_nsz_0_x_defaultenv_signaling(<2 x float> %a) 
#1 {
+; CHECK-LABEL: @fold_fadd_vec_nsz_0_x_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz <2 x float> 
@llvm.experimental.constrained.fadd.v2f32(<2 x float> zeroinitializer, <2 x 
float> [[A1:%.*]], metadata !"round.tonearest", metadata !"fpexcept.ignore") 
#[[ATTR0]]
+; CHECK-NEXT:    ret <2 x float> [[A]]
+;
+  %add = call nsz <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x 
float> zeroinitializer, <2 x float> %a, metadata !"round.tonearest", metadata 
!"fpexcept.ignore") #0
+  ret <2 x float> %add
+}
+
 ; TODO: Canonicalize the order of the arguments. Then this will fire.
 define float @fold_fadd_nsz_0_x_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fold_fadd_nsz_0_x_ebmaytrap(
@@ -460,3 +564,4 @@ declare float 
@llvm.experimental.constrained.fadd.f32(float, float, metadata, me
 declare <2 x float> @llvm.experimental.constrained.fadd.v2f32(<2 x float>, <2 
x float>, metadata, metadata) #0
 
 attributes #0 = { strictfp }
+attributes #1 = { signaling_nans strictfp }
diff --git a/llvm/test/Transforms/InstSimplify/strictfp-fsub.ll 
b/llvm/test/Transforms/InstSimplify/strictfp-fsub.ll
index b55519e8374b6..ca493b1f116e3 100644
--- a/llvm/test/Transforms/InstSimplify/strictfp-fsub.ll
+++ b/llvm/test/Transforms/InstSimplify/strictfp-fsub.ll
@@ -9,6 +9,7 @@
 ; fsub X, +0 ==> X
 ;
 
+; Folds: sNaNs are not expected and rounding is not downward.
 define float @fsub_x_p0_defaultenv(float %a) #0 {
 ; CHECK-LABEL: @fsub_x_p0_defaultenv(
 ; CHECK-NEXT:    ret float [[A:%.*]]
@@ -17,16 +18,36 @@ define float @fsub_x_p0_defaultenv(float %a) #0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Does not fold: sNaNs are possible.
+define float @fsub_x_p0_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_x_p0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float %a, float 
0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %ret
+}
+
+; Folds: sNaNs are not expected and rounding is not downward.
 define float @fsub_x_p0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fsub_x_p0_ebmaytrap(
-; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
-; CHECK-NEXT:    ret float [[RET]]
+; CHECK-NEXT:    ret float [[RET:%.*]]
+;
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float %a, float 
0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_x_p0_ebmaytrap_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_x_p0_ebmaytrap_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    ret float [[A]]
 ;
   %ret = call float @llvm.experimental.constrained.fsub.f32(float %a, float 
0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
   ret float %ret
 }
 
+; Folds: sNaNs are not expected and rounding is not downward.
 define float @fsub_nnan_x_p0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fsub_nnan_x_p0_ebmaytrap(
 ; CHECK-NEXT:    ret float [[A:%.*]]
@@ -35,16 +56,27 @@ define float @fsub_nnan_x_p0_ebmaytrap(float %a) #0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Folds: sNaNs are not expected and rounding is not downward.
 define float @fsub_x_p0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fsub_x_p0_ebstrict(
 ; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float %a, float 
0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_x_p0_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_x_p0_ebstrict_signaling(
+; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %ret = call float @llvm.experimental.constrained.fsub.f32(float %a, float 
0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
   ret float %ret
 }
 
+; Folds: sNaNs are not expected and rounding is not downward.
 ; The instruction is expected to remain, but the result isn't used.
 define float @fsub_nnan_x_p0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fsub_nnan_x_p0_ebstrict(
@@ -56,9 +88,20 @@ define float @fsub_nnan_x_p0_ebstrict(float %a) #0 {
 }
 
 ; Test with a fast math flag set but that flag is not "nnan".
+; Folds: sNaNs are not expected and rounding is not downward.
 define float @fsub_ninf_x_p0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fsub_ninf_x_p0_ebstrict(
 ; CHECK-NEXT:    [[RET:%.*]] = call ninf float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call ninf float @llvm.experimental.constrained.fsub.f32(float %a, 
float 0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_ninf_x_p0_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_ninf_x_p0_ebstrict_signaling(
+; CHECK-NEXT:    [[RET:%.*]] = call ninf float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float 0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %ret = call ninf float @llvm.experimental.constrained.fsub.f32(float %a, 
float 0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
@@ -95,6 +138,16 @@ define float @fsub_nsz_x_p0_neginf(float %a) #0 {
   ret float %ret
 }
 
+; Does not fold: sNaNs are possible.
+define float @fsub_nsz_x_p0_neginf_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_nsz_x_p0_neginf_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.downward", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float 0.0, metadata !"round.downward", metadata !"fpexcept.ignore")
+  ret float %ret
+}
+
 ; With nsz we don't have to worry about -0.0 so the transform is valid.
 define float @fsub_nsz_x_p0_dynamic(float %a) #0 {
 ; CHECK-LABEL: @fsub_nsz_x_p0_dynamic(
@@ -104,6 +157,16 @@ define float @fsub_nsz_x_p0_dynamic(float %a) #0 {
   ret float %ret
 }
 
+; Does not fold: sNaNs are possible.
+define float @fsub_nsz_x_p0_dynamic_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_nsz_x_p0_dynamic_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float 0.000000e+00, 
metadata !"round.dynamic", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float 0.0, metadata !"round.dynamic", metadata !"fpexcept.ignore")
+  ret float %ret
+}
+
 ;
 ; fsub X, -0 ==> X, when we know X is not -0
 ; (fast math flag: nsz)
@@ -117,11 +180,30 @@ define float @fold_fsub_nsz_x_n0_defaultenv(float %a) #0 {
   ret float %sub
 }
 
-; Missing nnan: must not fire.
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_nsz_x_n0_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_nsz_x_n0_defaultenv_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %sub = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %sub
+}
+
+; Folds: sNaNs are not expected and nsz.
 define float @fold_fsub_nsz_x_n0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fold_fsub_nsz_x_n0_ebmaytrap(
-; CHECK-NEXT:    [[SUB:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
-; CHECK-NEXT:    ret float [[SUB]]
+; CHECK-NEXT:    ret float [[SUB:%.*]]
+;
+  %sub = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  ret float %sub
+}
+
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_nsz_x_n0_ebmaytrap_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_nsz_x_n0_ebmaytrap_signaling(
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A1:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    ret float [[A]]
 ;
   %sub = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
   ret float %sub
@@ -135,10 +217,20 @@ define float @fold_fsub_nnan_nsz_x_n0_ebmaytrap(float %a) 
#0 {
   ret float %sub
 }
 
-; Missing nnan: must not fire.
+; Folds: sNaNs are not expected and nsz.
 define float @fold_fsub_nsz_x_n0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fold_fsub_nsz_x_n0_ebstrict(
 ; CHECK-NEXT:    [[SUB:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %sub = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %sub
+}
+
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_nsz_x_n0_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_nsz_x_n0_ebstrict_signaling(
+; CHECK-NEXT:    [[SUB:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float [[A:%.*]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[SUB]]
 ;
   %sub = call nsz float @llvm.experimental.constrained.fsub.f32(float %a, 
float -0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
@@ -170,11 +262,22 @@ define float @fold_fsub_fabs_x_n0_defaultenv(float %a) #0 
{
   ret float %sub
 }
 
-; Missing nnan: must not fire.
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_fabs_x_n0_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_fabs_x_n0_defaultenv_signaling(
+; CHECK-NEXT:    [[ABSA1:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
+; CHECK-NEXT:    [[ABSA:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[ABSA1]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[ABSA]]
+;
+  %absa = call float @llvm.fabs.f32(float %a) #0
+  %sub = call float @llvm.experimental.constrained.fsub.f32(float %absa, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %sub
+}
+
+; Folds: sNaNs are not expected and no -0.0.
 define float @fold_fsub_fabs_x_n0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fold_fsub_fabs_x_n0_ebmaytrap(
-; CHECK-NEXT:    [[ABSA:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
-; CHECK-NEXT:    [[SUB:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[ABSA]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    [[SUB:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
 ; CHECK-NEXT:    ret float [[SUB]]
 ;
   %absa = call float @llvm.fabs.f32(float %a) #0
@@ -182,6 +285,18 @@ define float @fold_fsub_fabs_x_n0_ebmaytrap(float %a) #0 {
   ret float %sub
 }
 
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_fabs_x_n0_ebmaytrap_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_fabs_x_n0_ebmaytrap_signaling(
+; CHECK-NEXT:    [[ABSA1:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
+; CHECK-NEXT:    [[ABSA:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[ABSA1]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    ret float [[ABSA]]
+;
+  %absa = call float @llvm.fabs.f32(float %a) #0
+  %sub = call float @llvm.experimental.constrained.fsub.f32(float %absa, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  ret float %sub
+}
+
 define float @fold_fsub_fabs_nnan_x_n0_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fold_fsub_fabs_nnan_x_n0_ebmaytrap(
 ; CHECK-NEXT:    [[ABSA:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
@@ -192,11 +307,23 @@ define float @fold_fsub_fabs_nnan_x_n0_ebmaytrap(float 
%a) #0 {
   ret float %sub
 }
 
-; Missing nnan: must not fire.
+; Folds: sNaNs are not expected and no -0.0.
 define float @fold_fsub_fabs_x_n0_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fold_fsub_fabs_x_n0_ebstrict(
 ; CHECK-NEXT:    [[ABSA:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
 ; CHECK-NEXT:    [[SUB:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[ABSA]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[ABSA]]
+;
+  %absa = call float @llvm.fabs.f32(float %a) #0
+  %sub = call float @llvm.experimental.constrained.fsub.f32(float %absa, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %sub
+}
+
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_fabs_x_n0_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fold_fsub_fabs_x_n0_ebstrict_signaling(
+; CHECK-NEXT:    [[ABSA:%.*]] = call float @llvm.fabs.f32(float [[A:%.*]]) 
#[[ATTR0]]
+; CHECK-NEXT:    [[SUB:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[ABSA]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[SUB]]
 ;
   %absa = call float @llvm.fabs.f32(float %a) #0
@@ -226,6 +353,18 @@ define float @fold_fsub_sitofp_x_n0_defaultenv(i32 %a) #0 {
   ret float %sub
 }
 
+; Does not fold: sNaNs are possible.
+define float @fold_fsub_sitofp_x_n0_defaultenv_signaling(i32 %a) #1 {
+; CHECK-LABEL: @fold_fsub_sitofp_x_n0_defaultenv_signaling(
+; CHECK-NEXT:    [[FPA:%.*]] = call float 
@llvm.experimental.constrained.sitofp.f32.i32(i32 [[A:%.*]], metadata 
!"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    [[SUB:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float [[FPA]], float -0.000000e+00, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[SUB]]
+;
+  %fpa = call float @llvm.experimental.constrained.sitofp.f32.i32(i32 %a, 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  %sub = call float @llvm.experimental.constrained.fsub.f32(float %fpa, float 
-0.0, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %sub
+}
+
 ;
 ; fsub -0.0, (fneg X) ==> X
 ;
@@ -239,12 +378,34 @@ define float @fsub_fneg_n0_fnX_defaultenv(float %a) #0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_n0_fnX_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_n0_fnX_defaultenv_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A1:%.*]]
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float -0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %nega = fneg float %a
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float -0.0, float 
%nega, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %ret
+}
+
+; Folds: sNaNs are not expected and subtrahend is fneg.
 define float @fsub_fneg_n0_fnX_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fsub_fneg_n0_fnX_ebmaytrap(
-; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float -0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
-; CHECK-NEXT:    ret float [[RET]]
+; CHECK-NEXT:    ret float [[RET:%.*]]
+;
+  %nega = fneg float %a
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float -0.0, float 
%nega, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_n0_fnX_ebmaytrap_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_n0_fnX_ebmaytrap_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A1:%.*]]
+; CHECK-NEXT:    [[A:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float -0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    ret float [[A]]
 ;
   %nega = fneg float %a
   %ret = call float @llvm.experimental.constrained.fsub.f32(float -0.0, float 
%nega, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
@@ -260,11 +421,23 @@ define float @fsub_fneg_nnan_n0_fnX_ebmaytrap(float %a) 
#0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Folds: sNaNs are not expected and no -0.0.
 define float @fsub_fneg_n0_fnX_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fsub_fneg_n0_fnX_ebstrict(
 ; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
 ; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float -0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %nega = fneg float %a
+  %ret = call float @llvm.experimental.constrained.fsub.f32(float -0.0, float 
%nega, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_n0_fnX_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_n0_fnX_ebstrict_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = call float 
@llvm.experimental.constrained.fsub.f32(float -0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %nega = fneg float %a
@@ -361,12 +534,34 @@ define float @fsub_fneg_nsz_p0_fnX_defaultenv(float %a) 
#0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_nsz_p0_fnX_defaultenv_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_nsz_p0_fnX_defaultenv_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A1:%.*]]
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float 0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.ignore")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %nega = fneg float %a
+  %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float 0.0, 
float %nega, metadata !"round.tonearest", metadata !"fpexcept.ignore")
+  ret float %ret
+}
+
+; Folds: sNaNs are not expected and nsz.
 define float @fsub_fneg_nsz_p0_fnX_ebmaytrap(float %a) #0 {
 ; CHECK-LABEL: @fsub_fneg_nsz_p0_fnX_ebmaytrap(
-; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
-; CHECK-NEXT:    [[RET:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float 0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
-; CHECK-NEXT:    ret float [[RET]]
+; CHECK-NEXT:    ret float [[RET:%.*]]
+;
+  %nega = fneg float %a
+  %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float 0.0, 
float %nega, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_nsz_p0_fnX_ebmaytrap_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_nsz_p0_fnX_ebmaytrap_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A1:%.*]]
+; CHECK-NEXT:    [[A:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float 0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.maytrap")
+; CHECK-NEXT:    ret float [[A]]
 ;
   %nega = fneg float %a
   %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float 0.0, 
float %nega, metadata !"round.tonearest", metadata !"fpexcept.maytrap")
@@ -382,11 +577,23 @@ define float @fsub_fneg_nsz_nnan_p0_fnX_ebmaytrap(float 
%a) #0 {
   ret float %ret
 }
 
-; Missing nnan: must not fire.
+; Folds: sNaNs are not expected and nsz.
 define float @fsub_fneg_nsz_p0_fnX_ebstrict(float %a) #0 {
 ; CHECK-LABEL: @fsub_fneg_nsz_p0_fnX_ebstrict(
 ; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
 ; CHECK-NEXT:    [[RET:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float 0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.strict")
+; CHECK-NEXT:    ret float [[A]]
+;
+  %nega = fneg float %a
+  %ret = call nsz float @llvm.experimental.constrained.fsub.f32(float 0.0, 
float %nega, metadata !"round.tonearest", metadata !"fpexcept.strict")
+  ret float %ret
+}
+
+; Does not fold: sNaNs are possible.
+define float @fsub_fneg_nsz_p0_fnX_ebstrict_signaling(float %a) #1 {
+; CHECK-LABEL: @fsub_fneg_nsz_p0_fnX_ebstrict_signaling(
+; CHECK-NEXT:    [[NEGA:%.*]] = fneg float [[A:%.*]]
+; CHECK-NEXT:    [[RET:%.*]] = call nsz float 
@llvm.experimental.constrained.fsub.f32(float 0.000000e+00, float [[NEGA]], 
metadata !"round.tonearest", metadata !"fpexcept.strict")
 ; CHECK-NEXT:    ret float [[RET]]
 ;
   %nega = fneg float %a
@@ -723,3 +930,4 @@ declare float 
@llvm.experimental.constrained.fsub.f32(float, float, metadata, me
 declare float @llvm.experimental.constrained.sitofp.f32.i32(i32, metadata, 
metadata)
 
 attributes #0 = { strictfp }
+attributes #1 = { signaling_nans strictfp }

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