atmnpatel updated this revision to Diff 298736.
atmnpatel added a comment.

nit.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D86844/new/

https://reviews.llvm.org/D86844

Files:
  clang/test/Misc/loop-opt-setup.c
  llvm/include/llvm/Transforms/Utils/LoopUtils.h
  llvm/lib/Transforms/Scalar/LoopDeletion.cpp
  llvm/lib/Transforms/Utils/LoopUtils.cpp
  llvm/test/Other/loop-deletion-printer.ll
  llvm/test/Other/loop-pm-invalidation.ll
  llvm/test/Transforms/LICM/2003-02-27-PreheaderProblem.ll
  llvm/test/Transforms/LoopDeletion/2017-07-11-incremental-dt.ll
  llvm/test/Transforms/LoopDeletion/basic-remark.ll
  llvm/test/Transforms/LoopDeletion/diundef.ll
  llvm/test/Transforms/LoopDeletion/invalidation.ll
  llvm/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
  llvm/test/Transforms/LoopDeletion/multiple-exits.ll
  llvm/test/Transforms/LoopDeletion/mustprogress.ll
  llvm/test/Transforms/LoopDeletion/unreachable-loops.ll
  llvm/test/Transforms/LoopDeletion/use-in-unreachable.ll
  llvm/test/Transforms/SCCP/calltest.ll
  llvm/test/Transforms/SimpleLoopUnswitch/pr37888.ll

Index: llvm/test/Transforms/SimpleLoopUnswitch/pr37888.ll
===================================================================
--- llvm/test/Transforms/SimpleLoopUnswitch/pr37888.ll
+++ llvm/test/Transforms/SimpleLoopUnswitch/pr37888.ll
@@ -7,7 +7,7 @@
 
 target triple = "x86_64-unknown-linux-gnu"
 
-define void @pr37888() {
+define void @pr37888() willreturn {
 ; CHECK-LABEL: define void @pr37888()
 entry:
   %tobool = icmp ne i16 undef, 0
Index: llvm/test/Transforms/SCCP/calltest.ll
===================================================================
--- llvm/test/Transforms/SCCP/calltest.ll
+++ llvm/test/Transforms/SCCP/calltest.ll
@@ -4,7 +4,7 @@
 %empty = type {}
 declare %empty @has_side_effects()
 
-define double @test_0(i32 %param) {
+define double @test_0(i32 %param) willreturn {
 ; CHECK-LABEL: @test_0(
 ; CHECK-NOT: br
 entry:
Index: llvm/test/Transforms/LoopDeletion/use-in-unreachable.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/use-in-unreachable.ll
+++ llvm/test/Transforms/LoopDeletion/use-in-unreachable.ll
@@ -3,7 +3,7 @@
 ; Checking that possible users of instruction from the loop in
 ; unreachable blocks are handled.
 
-define i64 @foo() {
+define i64 @foo() willreturn {
 entry:
   br label %invloop
 ; CHECK-LABEL-NOT: invloop
Index: llvm/test/Transforms/LoopDeletion/unreachable-loops.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/unreachable-loops.ll
+++ llvm/test/Transforms/LoopDeletion/unreachable-loops.ll
@@ -216,7 +216,7 @@
 ; Show recursive deletion of loops. Since we start with subloops and progress outward 
 ; to parent loop, we first delete the loop L2. Now loop L1 becomes a non-loop since it's backedge
 ; from L2's preheader to L1's exit block is never taken. So, L1 gets deleted as well.
-define void @test8(i64 %n) {
+define void @test8(i64 %n) #0 {
 ; CHECK-LABEL: test8
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br label %exit
@@ -318,7 +318,7 @@
 ; deleted.
 ; In the next iteration, since L2 is never executed and has no subloops, we delete
 ; L2 as well. Finally, the outermost loop L1 is deleted.
-define void @test11(i64 %n) {
+define void @test11(i64 %n) #0 {
 ; CHECK-LABEL: test11
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br label %exit
@@ -355,7 +355,7 @@
 
 
 ; 2 edges from a single exiting block to the exit block.
-define i64 @test12(i64 %n){
+define i64 @test12(i64 %n) #0 {
 ;CHECK-LABEL: @test12
 ; CHECK-NOT: L1:
 ; CHECK-NOT: L1Latch:
@@ -392,7 +392,7 @@
 }
 
 ; multiple edges to exit block from the same exiting blocks
-define i64 @test13(i64 %n) {
+define i64 @test13(i64 %n) #0 {
 ; CHECK-LABEL: @test13
 ; CHECK-NOT: L1:
 ; CHECK-NOT: L1Latch:
@@ -433,3 +433,5 @@
   %y.phi = phi i64 [ 10, %L1Block ], [ 10, %L1Block ], [ %y.next, %L1 ], [ 30, %L1Latch ], [ 30, %L1Latch ]
   ret i64 %y.phi
 }
+
+attributes #0 = { willreturn }
Index: llvm/test/Transforms/LoopDeletion/mustprogress.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/mustprogress.ll
+++ llvm/test/Transforms/LoopDeletion/mustprogress.ll
@@ -14,7 +14,9 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[FOR_END:%.*]]
 ; CHECK:       for.end:
-; CHECK-NEXT:    unreachable
+; CHECK-NEXT:    br label [[FOR_COND1:%.*]]
+; CHECK:       for.cond1:
+; CHECK-NEXT:    br label [[FOR_COND1]]
 ;
 entry:
   br label %for.cond
@@ -43,7 +45,9 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    br label [[FOR_END:%.*]]
 ; CHECK:       for.end:
-; CHECK-NEXT:    unreachable
+; CHECK-NEXT:    br label [[FOR_COND1:%.*]]
+; CHECK:       for.cond1:
+; CHECK-NEXT:    br label [[FOR_COND1]]
 ;
 entry:
   br label %for.cond
Index: llvm/test/Transforms/LoopDeletion/multiple-exits.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/multiple-exits.ll
+++ llvm/test/Transforms/LoopDeletion/multiple-exits.ll
@@ -10,7 +10,7 @@
 ; RUN: opt < %s -passes=loop-deletion -S | FileCheck %s --check-prefixes=CHECK,AFTER
 
 
-define void @foo(i64 %n, i64 %m) nounwind {
+define void @foo(i64 %n, i64 %m) #0 {
 ; CHECK-LABEL: @foo(
 
 entry:
@@ -43,7 +43,7 @@
 ; CHECK-NEXT:    ret void
 }
 
-define i64 @bar(i64 %n, i64 %m, i64 %maybe_zero) nounwind {
+define i64 @bar(i64 %n, i64 %m, i64 %maybe_zero) #0 {
 ; CHECK-LABEL: @bar(
 
 entry:
@@ -95,7 +95,7 @@
 
 ; This function has a loop which looks like @bar's but that cannot be deleted
 ; because which path we exit through determines which value is selected.
-define i64 @baz(i64 %n, i64 %m, i64 %maybe_zero) nounwind {
+define i64 @baz(i64 %n, i64 %m, i64 %maybe_zero) #0 {
 ; CHECK-LABEL:  @baz(
 
 entry:
@@ -136,3 +136,5 @@
 ; CHECK-NEXT:  %[[X:.*]] = phi i64 [ 12, %bb ], [ 10, %bb2 ], [ 10, %bb3 ]
 ; CHECK-NEXT:  ret i64 %[[X]]
 }
+
+attributes #0 = { nounwind willreturn }
\ No newline at end of file
Index: llvm/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
+++ llvm/test/Transforms/LoopDeletion/multiple-exit-conditions.ll
@@ -11,7 +11,7 @@
 ; CHECK:      return:
 ; CHECK-NEXT:   ret void
 
-define void @foo(i64 %n, i64 %m) nounwind {
+define void @foo(i64 %n, i64 %m) nounwind willreturn {
 entry:
   br label %bb
 
Index: llvm/test/Transforms/LoopDeletion/invalidation.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/invalidation.ll
+++ llvm/test/Transforms/LoopDeletion/invalidation.ll
@@ -8,7 +8,7 @@
 ; RUN:     | FileCheck %s --check-prefixes=CHECK,AFTER
 
 
-define void @foo(i64 %n, i64 %m) nounwind {
+define void @foo(i64 %n, i64 %m) nounwind willreturn {
 ; CHECK-LABEL: @foo(
 
 entry:
Index: llvm/test/Transforms/LoopDeletion/diundef.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/diundef.ll
+++ llvm/test/Transforms/LoopDeletion/diundef.ll
@@ -5,7 +5,7 @@
 
 @a = common local_unnamed_addr global i32 0, align 4, !dbg !0
 
-define i32 @b() local_unnamed_addr !dbg !12 {
+define i32 @b() local_unnamed_addr willreturn !dbg !12 {
 entry:
   call void @llvm.dbg.value(metadata i32 0, metadata !16, metadata !DIExpression()), !dbg !17
   br label %for.cond, !dbg !18
Index: llvm/test/Transforms/LoopDeletion/basic-remark.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/basic-remark.ll
+++ llvm/test/Transforms/LoopDeletion/basic-remark.ll
@@ -10,7 +10,7 @@
 ; CHECK-NEXT: Args:
 ; CHECK-NEXT:   - String:          Loop deleted because it is invariant
 ; CHECK-NEXT: ...
-define i32 @main() local_unnamed_addr #0 {
+define i32 @main() local_unnamed_addr willreturn {
 entry:
   br label %for.cond, !dbg !9
 
Index: llvm/test/Transforms/LoopDeletion/2017-07-11-incremental-dt.ll
===================================================================
--- llvm/test/Transforms/LoopDeletion/2017-07-11-incremental-dt.ll
+++ llvm/test/Transforms/LoopDeletion/2017-07-11-incremental-dt.ll
@@ -14,7 +14,7 @@
 ; DT:     [3] %for.body
 ; DT:       [4] %for.cond3.loopexit
 
-define i32 @fn1() {
+define i32 @fn1() willreturn {
 entry:
   br label %for.cond
 
Index: llvm/test/Transforms/LICM/2003-02-27-PreheaderProblem.ll
===================================================================
--- llvm/test/Transforms/LICM/2003-02-27-PreheaderProblem.ll
+++ llvm/test/Transforms/LICM/2003-02-27-PreheaderProblem.ll
@@ -6,7 +6,7 @@
 ; RUN: opt < %s -licm -loop-deletion -simplifycfg -S | \
 ; RUN:   not grep "br "
 
-define i32 @main(i32 %argc) {
+define i32 @main(i32 %argc) willreturn {
 ; <label>:0
 	br label %bb5
 bb5:		; preds = %bb5, %0
Index: llvm/test/Other/loop-pm-invalidation.ll
===================================================================
--- llvm/test/Other/loop-pm-invalidation.ll
+++ llvm/test/Other/loop-pm-invalidation.ll
@@ -227,7 +227,7 @@
   ret void
 }
 
-define void @dead_loop() {
+define void @dead_loop() willreturn {
 ; CHECK-LOOP-INV: Starting {{.*}}Function pass manager run
 ; CHECK-LOOP-INV-NEXT: Starting {{.*}}Function pass manager run
 ; CHECK-LOOP-INV-NEXT: Running pass: LoopSimplifyPass
Index: llvm/test/Other/loop-deletion-printer.ll
===================================================================
--- llvm/test/Other/loop-deletion-printer.ll
+++ llvm/test/Other/loop-deletion-printer.ll
@@ -14,7 +14,7 @@
 ; DELETED-BUT-PRINTED: IR Dump {{.*}}LoopDeletionPass {{.*invalidated:}}
 ; DELETED-BUT-PRINTED-NOT: IR Dump {{.*}}LoopInstSimplifyPass
 
-define void @deleteme() {
+define void @deleteme() willreturn {
 entry:
   br label %loop
 loop:
Index: llvm/lib/Transforms/Utils/LoopUtils.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUtils.cpp
+++ llvm/lib/Transforms/Utils/LoopUtils.cpp
@@ -63,6 +63,7 @@
 
 static const char *LLVMLoopDisableNonforced = "llvm.loop.disable_nonforced";
 static const char *LLVMLoopDisableLICM = "llvm.licm.disable";
+static const char *LLVMLoopMustProgress = "llvm.loop.mustprogress";
 
 bool llvm::formDedicatedExitBlocks(Loop *L, DominatorTree *DT, LoopInfo *LI,
                                    MemorySSAUpdater *MSSAU,
@@ -404,6 +405,10 @@
   return getBooleanLoopAttribute(L, LLVMLoopDisableLICM);
 }
 
+bool llvm::hasMustProgress(const Loop *L) {
+  return getBooleanLoopAttribute(L, LLVMLoopMustProgress);
+}
+
 TransformationMode llvm::hasUnrollTransformation(Loop *L) {
   if (getBooleanLoopAttribute(L, "llvm.loop.unroll.disable"))
     return TM_SuppressedByUser;
Index: llvm/lib/Transforms/Scalar/LoopDeletion.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/LoopDeletion.cpp
+++ llvm/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -56,10 +56,10 @@
   for (PHINode &P : ExitBlock->phis()) {
     Value *incoming = P.getIncomingValueForBlock(ExitingBlocks[0]);
 
-    // Make sure all exiting blocks produce the same incoming value for the exit
-    // block.  If there are different incoming values for different exiting
-    // blocks, then it is impossible to statically determine which value should
-    // be used.
+    // Make sure all exiting blocks produce the same incoming value for the
+    // exit block.  If there are different incoming values for different
+    // exiting blocks, then it is impossible to statically determine which
+    // value should be used.
     AllOutgoingValuesSame =
         all_of(makeArrayRef(ExitingBlocks).slice(1), [&](BasicBlock *BB) {
           return incoming == P.getIncomingValueForBlock(BB);
@@ -199,7 +199,7 @@
   // blocks. Otherwise, we'd be in the situation of needing to be able to
   // solve statically which exit block will be branched to, or trying to
   // preserve the branching logic in a loop invariant manner.
-  if (!ExitBlock && L->getNumExitBlocks() != 0) {
+  if (!ExitBlock) {
     LLVM_DEBUG(dbgs() << "Deletion requires single exit block\n");
     return LoopDeletionResult::Unmodified;
   }
@@ -214,8 +214,10 @@
   // Don't remove loops for which we can't solve the trip count.
   // They could be infinite, in which case we'd be changing program behavior.
   const SCEV *S = SE.getConstantMaxBackedgeTakenCount(L);
-  if (isa<SCEVCouldNotCompute>(S)) {
-    LLVM_DEBUG(dbgs() << "Could not compute SCEV MaxBackedgeTakenCount.\n");
+  if (isa<SCEVCouldNotCompute>(S) &&
+      !L->getHeader()->getParent()->mustProgress() && !hasMustProgress(L)) {
+    LLVM_DEBUG(dbgs() << "Could not compute SCEV MaxBackedgeTakenCount and was "
+                         "not required to make progress.\n");
     return Changed ? LoopDeletionResult::Modified
                    : LoopDeletionResult::Unmodified;
   }
Index: llvm/include/llvm/Transforms/Utils/LoopUtils.h
===================================================================
--- llvm/include/llvm/Transforms/Utils/LoopUtils.h
+++ llvm/include/llvm/Transforms/Utils/LoopUtils.h
@@ -229,6 +229,9 @@
 /// Look for the loop attribute that disables the LICM transformation heuristics.
 bool hasDisableLICMTransformsHint(const Loop *L);
 
+/// Look for the loop attribute that requires progress within the loop.
+bool hasMustProgress(const Loop *L);
+
 /// The mode sets how eager a transformation should be applied.
 enum TransformationMode {
   /// The pass can use heuristics to determine whether a transformation should
Index: clang/test/Misc/loop-opt-setup.c
===================================================================
--- clang/test/Misc/loop-opt-setup.c
+++ clang/test/Misc/loop-opt-setup.c
@@ -25,6 +25,6 @@
 
 // Check br i1 to make sure the loop is gone, there will still be a label branch for the infinite loop.
 // CHECK-LABEL: Helper
-// CHECK: br label
+// CHECK: entry:
 // CHECK-NOT: br i1
-// CHECK: br label
+// CHECK-NEXT: ret void
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