[PATCH] D89190: [MemCpyOpt] Don't shorten memset if destination observable through unwinding

[Nikita Popov via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG39c39e8a7f09: [MemCpyOpt] Don't shorten memset if destination observable through unwinding (authored by nikic).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D89190/new/

https://reviews.llvm.org/D89190

Files:
  llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
  llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll


Index: llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
===================================================================
--- llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
+++ llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
@@ -193,13 +193,9 @@
 
 define void @test_throwing_call(i8* %src, i64 %src_size, i8* %dst, i64 %dst_size, i8 %c) {
 ; CHECK-LABEL: @test_throwing_call(
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* [[DST:%.*]], i8 [[C:%.*]], i64 [[DST_SIZE:%.*]], i1 false)
 ; CHECK-NEXT:    call void @call() [[ATTR2:#.*]]
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp ule i64 [[DST_SIZE:%.*]], [[SRC_SIZE:%.*]]
-; CHECK-NEXT:    [[TMP2:%.*]] = sub i64 [[DST_SIZE]], [[SRC_SIZE]]
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP1]], i64 0, i64 [[TMP2]]
-; CHECK-NEXT:    [[TMP4:%.*]] = getelementptr i8, i8* [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
-; CHECK-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC:%.*]], i64 [[SRC_SIZE:%.*]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
   call void @llvm.memset.p0i8.i64(i8* %dst, i8 %c, i64 %dst_size, i1 false)
Index: llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -1050,6 +1050,17 @@
   Value *DestSize = MemSet->getLength();
   Value *SrcSize = MemCpy->getLength();
 
+  // If the destination might be accessible by the caller, make sure we cannot
+  // unwind between the memset and the memcpy.
+  if (!MemCpy->getFunction()->doesNotThrow() &&
+      !isa<AllocaInst>(getUnderlyingObject(Dest))) {
+    for (const Instruction &I :
+         make_range(MemSet->getIterator(), MemCpy->getIterator())) {
+      if (I.mayThrow())
+        return false;
+    }
+  }
+
   // By default, create an unaligned memset.
   unsigned Align = 1;
   // If Dest is aligned, and SrcSize is constant, use the minimum alignment


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