[llvm] r235258 - [MemCpyOpt] Promote both memset/memcpy sizes if differently typed.

[David Majnemer]

On Sat, Apr 18, 2015 at 6:57 PM, Ahmed Bougacha <ahmed.bougacha at gmail.com>
wrote:

> Author: ab
> Date: Sat Apr 18 12:57:41 2015
> New Revision: 235258
>
> URL: http://llvm.org/viewvc/llvm-project?rev=235258&view=rev
> Log:
> [MemCpyOpt] Promote both memset/memcpy sizes if differently typed.
>
> Followup to r235232, which caused PR23278.
>
> We can't assume the memset and memcpy sizes have the same type, as
> nothing in the language reference prevents that.
> Instead, zext both to i64 if they disagree.
>
> While there, robustify tests by using i8 %c rather than i8 0 for the
> memset character.
>
> Modified:
>     llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
>     llvm/trunk/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
>
> Modified: llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp?rev=235258&r1=235257&r2=235258&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/MemCpyOptimizer.cpp Sat Apr 18
> 12:57:41 2015
> @@ -876,6 +876,12 @@ bool MemCpyOpt::processMemSetMemCpyDepen
>
>    IRBuilder<> Builder(MemCpy->getNextNode());
>
> +  // If the sizes have different types (i32 vs i64), promote both to i64.
> +  if (DestSize->getType() != SrcSize->getType()) {
> +    DestSize = Builder.CreateZExt(DestSize, Builder.getInt64Ty());
> +    SrcSize = Builder.CreateZExt(SrcSize, Builder.getInt64Ty());
> +  }
> +
>

I don't think this is quite right, I can crash memcpyopt with:
define void @test_different_types_i32_i128(i8* %dst, i8* %src, i32
%dst_size, i128 %src_size, i8 %c) {
  call void @llvm.memset.p0i8.i32(i8* %dst, i8 %c, i32 %dst_size, i32 1, i1
false)
  call void @llvm.memcpy.p0i8.p0i8.i128(i8* %dst, i8* %src, i128 %src_size,
i32 1, i1 false)
  ret void
}

declare void @llvm.memcpy.p0i8.p0i8.i128(i8* nocapture, i8* nocapture
readonly, i128, i32, i1)
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1)

I think you instead need to figure out which type is bigger and zext the
smaller size to the larger type instead of choosing i64.



>    Value *MemsetLen =
>        Builder.CreateSelect(Builder.CreateICmpULE(DestSize, SrcSize),
>                             ConstantInt::getNullValue(DestSize->getType()),
>
> Modified:
> llvm/trunk/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll?rev=235258&r1=235257&r2=235258&view=diff
>
> ==============================================================================
> --- llvm/trunk/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
> (original)
> +++ llvm/trunk/test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
> Sat Apr 18 12:57:41 2015
> @@ -8,14 +8,44 @@ target datalayout = "e-m:o-i64:64-f80:12
>  ; CHECK-DAG: [[ULE:%[0-9]+]] = icmp ule i64 %dst_size, %src_size
>  ; CHECK-DAG: [[SIZEDIFF:%[0-9]+]] = sub i64 %dst_size, %src_size
>  ; CHECK-DAG: [[SIZE:%[0-9]+]] = select i1 [[ULE]], i64 0, i64 [[SIZEDIFF]]
> -; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[DST]], i8 0, i64
> [[SIZE]], i32 1, i1 false)
> +; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[DST]], i8 %c, i64
> [[SIZE]], i32 1, i1 false)
>  ; CHECK-NEXT: ret void
> -define void @test(i8* %src, i64 %src_size, i8* %dst, i64 %dst_size) {
> -  call void @llvm.memset.p0i8.i64(i8* %dst, i8 0, i64 %dst_size, i32 1,
> i1 false)
> +define void @test(i8* %src, i64 %src_size, i8* %dst, i64 %dst_size, i8
> %c) {
> +  call void @llvm.memset.p0i8.i64(i8* %dst, i8 %c, i64 %dst_size, i32 1,
> i1 false)
> +  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %src_size,
> i32 1, i1 false)
> +  ret void
> +}
> +
> +; CHECK-LABEL: define void @test_different_types_i32_i64
> +; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src,
> i64 %src_size, i32 1, i1 false)
> +; CHECK-DAG: [[DSTSIZE:%[0-9]+]] = zext i32 %dst_size to i64
> +; CHECK-DAG: [[DST:%[0-9]+]] = getelementptr i8, i8* %dst, i64 %src_size
> +; CHECK-DAG: [[ULE:%[0-9]+]] = icmp ule i64 [[DSTSIZE]], %src_size
> +; CHECK-DAG: [[SIZEDIFF:%[0-9]+]] = sub i64 [[DSTSIZE]], %src_size
> +; CHECK-DAG: [[SIZE:%[0-9]+]] = select i1 [[ULE]], i64 0, i64 [[SIZEDIFF]]
> +; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[DST]], i8 %c, i64
> [[SIZE]], i32 1, i1 false)
> +; CHECK-NEXT: ret void
> +define void @test_different_types_i32_i64(i8* %dst, i8* %src, i32
> %dst_size, i64 %src_size, i8 %c) {
> +  call void @llvm.memset.p0i8.i32(i8* %dst, i8 %c, i32 %dst_size, i32 1,
> i1 false)
>    call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %src_size,
> i32 1, i1 false)
>    ret void
>  }
>
> +; CHECK-LABEL: define void @test_different_types_i64_i32
> +; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %src,
> i32 %src_size, i32 1, i1 false)
> +; CHECK-DAG: [[SRCSIZE:%[0-9]+]] = zext i32 %src_size to i64
> +; CHECK-DAG: [[DST:%[0-9]+]] = getelementptr i8, i8* %dst, i64 [[SRCSIZE]]
> +; CHECK-DAG: [[ULE:%[0-9]+]] = icmp ule i64 %dst_size, [[SRCSIZE]]
> +; CHECK-DAG: [[SIZEDIFF:%[0-9]+]] = sub i64 %dst_size, [[SRCSIZE]]
> +; CHECK-DAG: [[SIZE:%[0-9]+]] = select i1 [[ULE]], i64 0, i64 [[SIZEDIFF]]
> +; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* [[DST]], i8 %c, i64
> [[SIZE]], i32 1, i1 false)
> +; CHECK-NEXT: ret void
> +define void @test_different_types_i64_i32(i8* %dst, i8* %src, i64
> %dst_size, i32 %src_size, i8 %c) {
> +  call void @llvm.memset.p0i8.i64(i8* %dst, i8 %c, i64 %dst_size, i32 1,
> i1 false)
> +  call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %src, i32 %src_size,
> i32 1, i1 false)
> +  ret void
> +}
> +
>  ; CHECK-LABEL: define void @test_align_same
>  ; CHECK: call void @llvm.memset.p0i8.i64(i8* {{.*}}, i8 0, i64 {{.*}},
> i32 8, i1 false)
>  define void @test_align_same(i8* %src, i8* %dst, i64 %dst_size) {
> @@ -52,3 +82,5 @@ define void @test_different_dst(i8* %dst
>
>  declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1)
>  declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture
> readonly, i64, i32, i1)
> +declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1)
> +declare void @llvm.memcpy.p0i8.p0i8.i32(i8* nocapture, i8* nocapture
> readonly, i32, i32, i1)
>
>
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