[llvm] 6bc5e86 - [MemCpyOpt] Account for case that MemInsertPoint == BI.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2020-09-04T14:04:08+01:00
New Revision: 6bc5e866bdba03fdd2d92bd72f3fce9c2973bf1f

URL: https://github.com/llvm/llvm-project/commit/6bc5e866bdba03fdd2d92bd72f3fce9c2973bf1f
DIFF: https://github.com/llvm/llvm-project/commit/6bc5e866bdba03fdd2d92bd72f3fce9c2973bf1f.diff

LOG: [MemCpyOpt] Account for case that MemInsertPoint == BI.

In that case, the new MemoryDef needs to be inserted *before*
MemInsertPoint.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
    llvm/test/Transforms/MemCpyOpt/preserve-memssa.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index aff08a2c366c..9011e36619d9 100644
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -423,8 +423,12 @@ Instruction *MemCpyOptPass::tryMergingIntoMemset(Instruction *StartInst,
     if (MSSAU) {
       assert(LastMemDef && MemInsertPoint &&
              "Both LastMemDef and MemInsertPoint need to be set");
-      auto *NewDef = cast<MemoryDef>(
-          MSSAU->createMemoryAccessAfter(AMemSet, LastMemDef, MemInsertPoint));
+      auto *NewDef =
+          cast<MemoryDef>(MemInsertPoint->getMemoryInst() == &*BI
+                              ? MSSAU->createMemoryAccessBefore(
+                                    AMemSet, LastMemDef, MemInsertPoint)
+                              : MSSAU->createMemoryAccessAfter(
+                                    AMemSet, LastMemDef, MemInsertPoint));
       MSSAU->insertDef(NewDef, /*RenameUses=*/true);
       LastMemDef = NewDef;
       MemInsertPoint = NewDef;

diff  --git a/llvm/test/Transforms/MemCpyOpt/preserve-memssa.ll b/llvm/test/Transforms/MemCpyOpt/preserve-memssa.ll
index 4e449ed5ff4f..f3c54579d9d0 100644
--- a/llvm/test/Transforms/MemCpyOpt/preserve-memssa.ll
+++ b/llvm/test/Transforms/MemCpyOpt/preserve-memssa.ll
@@ -123,6 +123,33 @@ entry:
   ret i8 %0
 }
 
+define void @test7([4 x i32]* %ptr) {
+; CHECK-LABEL: @test7(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds [4 x i32], [4 x i32]* [[PTR:%.*]], i64 0, i32 0
+; CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds [4 x i32], [4 x i32]* [[PTR]], i64 0, i32 1
+; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds [4 x i32], [4 x i32]* [[PTR]], i64 0, i32 2
+; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr inbounds [4 x i32], [4 x i32]* [[PTR]], i64 0, i32 3
+; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i32* [[TMP0]] to i8*
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP4]], i8 0, i64 16, i1 false)
+; CHECK-NEXT:    call void @clobber()
+; CHECK-NEXT:    ret void
+;
+entry:
+  %0 = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i64 0, i32 0
+  store i32 0, i32* %0, align 1
+  %1 = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i64 0, i32 1
+  store i32 0, i32* %1, align 1
+  %2 = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i64 0, i32 2
+  store i32 0, i32* %2, align 1
+  %3 = getelementptr inbounds [4 x i32], [4 x i32]* %ptr, i64 0, i32 3
+  store i32 0, i32* %3, align 1
+  call void @clobber()
+  ret void
+}
+
+declare void @clobber()
+
 ; Function Attrs: argmemonly nounwind willreturn
 declare void @llvm.lifetime.start.p0i8(i64 immarg, i8* nocapture) #0