https://github.com/andykaylor created
https://github.com/llvm/llvm-project/pull/69797
None
>From 856a471b40f19f5fcf6aab7591009555b6a3841f Mon Sep 17 00:00:00 2001
From: Andy Kaylor
Date: Fri, 20 Oct 2023 12:33:51 -0700
Subject: [PATCH 1/2] Update SimplifyIndVar.cpp
In SimplifyIndvar::replaceFloatIVWithIntegerIV() the return value of
getFPMantissaWidth() was being cast as an unsigned integer and then compared
with the number of bits needed to represent an integer that was cast to and
from a floating-point type. This is a problem because getFPMantissaWidth()
returns -1 if the type does not have a stable mantissa.
Currently the only type that returns -1 is ppc_fp128, so you'd need a pretty
big induction variable to cause a problem. However, this problem will be more
likely to be exposed when we implement support for decimal floating-point types.
Strictly speaking, what we want to know here is the size of the biggest integer
that can be represented exactly. We could get that information even with an
unstable mantissa width, but getFPMantissaWidth() won't do it.
---
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 1caf708bcc35254..45cbdd235898b28 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -664,7 +664,7 @@ bool
SimplifyIndvar::replaceFloatIVWithIntegerIV(Instruction *UseInst) {
MaskBits = SE->getSignedRange(IV).getMinSignedBits();
else
MaskBits = SE->getUnsignedRange(IV).getActiveBits();
- unsigned DestNumSigBits = UseInst->getType()->getFPMantissaWidth();
+ int DestNumSigBits = UseInst->getType()->getFPMantissaWidth();
if (MaskBits <= DestNumSigBits) {
for (User *U : UseInst->users()) {
// Match for fptosi/fptoui of sitofp and with same type.
>From 2524d41a34ccaa3932e5b4ab2876ea02744f6304 Mon Sep 17 00:00:00 2001
From: Andy Kaylor
Date: Fri, 20 Oct 2023 16:40:26 -0700
Subject: [PATCH 2/2] Fix build warning
This fixes a build warning caused by mixed signed/unsigned compare
---
llvm/lib/Transforms/Utils/SimplifyIndVar.cpp | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
index 45cbdd235898b28..a23ac41acaa58aa 100644
--- a/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyIndVar.cpp
@@ -659,11 +659,11 @@ bool
SimplifyIndvar::replaceFloatIVWithIntegerIV(Instruction *UseInst) {
Instruction *IVOperand = cast(UseInst->getOperand(0));
// Get the symbolic expression for this instruction.
const SCEV *IV = SE->getSCEV(IVOperand);
- unsigned MaskBits;
+ int MaskBits;
if (UseInst->getOpcode() == CastInst::SIToFP)
-MaskBits = SE->getSignedRange(IV).getMinSignedBits();
+MaskBits = (int)SE->getSignedRange(IV).getMinSignedBits();
else
-MaskBits = SE->getUnsignedRange(IV).getActiveBits();
+MaskBits = (int)SE->getUnsignedRange(IV).getActiveBits();
int DestNumSigBits = UseInst->getType()->getFPMantissaWidth();
if (MaskBits <= DestNumSigBits) {
for (User *U : UseInst->users()) {
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