[PATCH] D74083: MemCpyOpt cannot use ABI alignment even if it was not given

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune created this revision.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
aqjune added reviewers: gchatelet, lenary, nikic.

This patch fixes https://bugs.llvm.org/show_bug.cgi?id=44388 which incorrectly assigns an ABI alignment to memset when there was no explicit alignment given.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D74083

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


Index: llvm/test/Transforms/MemCpyOpt/form-memset.ll
===================================================================
--- llvm/test/Transforms/MemCpyOpt/form-memset.ll
+++ llvm/test/Transforms/MemCpyOpt/form-memset.ll
@@ -217,7 +217,7 @@
   tail call void @llvm.memset.p0i8.i64(i8* %1, i8 0, i64 12, i1 false)
   ret void
 ; CHECK-LABEL: @test6(
-; CHECK: call void @llvm.memset.p0i8.i64(i8* align 4 %2, i8 0, i64 24, i1 false)
+; CHECK: call void @llvm.memset.p0i8.i64(i8* %2, i8 0, i64 24, i1 false)
 }
 
 ; More aggressive heuristic
@@ -280,7 +280,7 @@
   ret void
 ; CHECK-LABEL: @test10(
 ; CHECK-NOT: memset
-; CHECK: call void @llvm.memset.p0i8.i64(i8* align 1 %P, i8 0, i64 42, i1 false)
+; CHECK: call void @llvm.memset.p0i8.i64(i8* %P, i8 0, i64 42, i1 false)
 ; CHECK-NOT: memset
 ; CHECK: ret void
 }
Index: llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -387,13 +387,8 @@
     // Get the starting pointer of the block.
     StartPtr = Range.StartPtr;
 
-    // Determine alignment
-    const Align Alignment = DL.getValueOrABITypeAlignment(
-        MaybeAlign(Range.Alignment),
-        cast<PointerType>(StartPtr->getType())->getElementType());
-
     AMemSet = Builder.CreateMemSet(StartPtr, ByteVal, Range.End - Range.Start,
-                                   Alignment);
+                                   MaybeAlign(Range.Alignment));
     LLVM_DEBUG(dbgs() << "Replace stores:\n"; for (Instruction *SI
                                                    : Range.TheStores) dbgs()
                                               << *SI << '\n';


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