[llvm] f025053 - [MemCpyOpt] Handle unusual memcpy element type

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2021-06-27T16:21:44+02:00
New Revision: f025053977f330152da081b7060a5d9cba0a9e22

URL: https://github.com/llvm/llvm-project/commit/f025053977f330152da081b7060a5d9cba0a9e22
DIFF: https://github.com/llvm/llvm-project/commit/f025053977f330152da081b7060a5d9cba0a9e22.diff

LOG: [MemCpyOpt] Handle unusual memcpy element type

Apparently, it is legal to use memcpy/memset with pointer types
other than i8*. Prior to 81fcdae68c5ff656c30032fd26c6a21af4c51dbb
this case was silently miscompiled, as the i8 offset calculation
was performed on some other type. Now it would crash due to a
type mismatch. Fix this by inserting an explicit bitcast to i8*.

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index 6016779ef3cf..b0b1a3ffbbcd 100644
--- a/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -1215,7 +1215,9 @@ bool MemCpyOptPass::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
   Value *MemsetLen = Builder.CreateSelect(
       Ule, ConstantInt::getNullValue(DestSize->getType()), SizeDiff);
   Instruction *NewMemSet = Builder.CreateMemSet(
-      Builder.CreateGEP(Builder.getInt8Ty(), Dest, SrcSize),
+      Builder.CreateGEP(Builder.getInt8Ty(),
+                        Builder.CreatePointerCast(Dest, Builder.getInt8PtrTy()),
+                        SrcSize),
       MemSet->getOperand(1), MemsetLen, MaybeAlign(Align));
 
   if (MSSAU) {

diff  --git a/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll b/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
index 987321607b3d..1a91d2e61ad6 100644
--- a/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
+++ b/llvm/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
@@ -296,8 +296,9 @@ define void @test_opaque_ptrs(ptr %src, i64 %src_size, ptr noalias %dst, i64 %ds
 ; 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, ptr [[DST:%.*]], i64 [[SRC_SIZE]]
-; CHECK-NEXT:    call void @llvm.memset.p0.i64(ptr align 1 [[TMP4]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    [[TMP4:%.*]] = bitcast ptr [[DST:%.*]] to i8*
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, i8* [[TMP4]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP5]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
 ; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr [[DST]], ptr [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
 ; CHECK-NEXT:    ret void
 ;
@@ -306,6 +307,22 @@ define void @test_opaque_ptrs(ptr %src, i64 %src_size, ptr noalias %dst, i64 %ds
   ret void
 }
 
+define void @test_weird_element_type(i16* %src, i64 %src_size, i16* noalias %dst, i64 %dst_size, i8 %c) {
+; CHECK-LABEL: @test_weird_element_type(
+; 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:%.*]] = bitcast i16* [[DST:%.*]] to i8*
+; CHECK-NEXT:    [[TMP5:%.*]] = getelementptr i8, i8* [[TMP4]], i64 [[SRC_SIZE]]
+; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* align 1 [[TMP5]], i8 [[C:%.*]], i64 [[TMP3]], i1 false)
+; CHECK-NEXT:    call void @llvm.memcpy.p0i16.p0i16.i64(i16* [[DST]], i16* [[SRC:%.*]], i64 [[SRC_SIZE]], i1 false)
+; CHECK-NEXT:    ret void
+;
+  call void @llvm.memset.p0i16.i64(i16* %dst, i8 %c, i64 %dst_size, i1 false)
+  call void @llvm.memcpy.p0i16.p0i16.i64(i16* %dst, i16* %src, i64 %src_size, i1 false)
+  ret void
+}
+
 declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i1)
 declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture readonly, i64, i1)
 declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i1)
@@ -314,4 +331,6 @@ declare void @llvm.memset.p0i8.i128(i8* nocapture, i8, i128, i1)
 declare void @llvm.memcpy.p0i8.p0i8.i128(i8* nocapture, i8* nocapture readonly, i128, i1)
 declare void @llvm.memset.p0.i64(ptr nocapture, i8, i64, i1)
 declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture readonly, i64, i1)
+declare void @llvm.memset.p0i16.i64(i16* nocapture, i8, i64, i1)
+declare void @llvm.memcpy.p0i16.p0i16.i64(i16* nocapture, i16* nocapture readonly, i64, i1)
 declare void @call()