6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-11-23 16:19:52 +00:00
Code Issues Projects Releases Wiki Activity

[MemCpyOpt] Use the raw i8* dest when optimizing memset+memcpy.

Browse Source 
MemIntrinsic::getDest() looks through pointer casts, and using it
directly when building the new GEP+memset results in stuff like:

  %0 = getelementptr i64* %p, i32 16
  %1 = bitcast i64* %0 to i8*
  call ..memset(i8* %1, ...)

instead of the correct:

  %0 = bitcast i64* %p to i8*
  %1 = getelementptr i8* %0, i32 16
  call ..memset(i8* %1, ...)

Instead, use getRawDest, which just gives you the i8* value.
While there, use the memcpy's dest, as it's live anyway.

In most cases, when the optimization triggers, the memset and memcpy
sizes are the same, so the built memset is 0-sized and eliminated.
The problem occurs when they're different.

Fixes a regression caused by r235232: PR23300.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235419 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Ahmed Bougacha
2015-04-21 21:28:33 +00:00
parent a42f6b9a58
commit 0f32a037ef
2 changed files with 18 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@@ -860,7 +860,8 @@ bool MemCpyOpt::processMemSetMemCpyDependence(MemCpyInst *MemCpy,
if (MemSet->getDest() != MemCpy->getDest()) if (MemSet->getDest() != MemCpy->getDest())
return false; return false;
Value *Dest = MemSet->getDest(); // Use the same i8* dest as the memcpy, killing the memset dest if different.
Value *Dest = MemCpy->getRawDest();
Value *DestSize = MemSet->getLength(); Value *DestSize = MemSet->getLength();
Value *SrcSize = MemCpy->getLength(); Value *SrcSize = MemCpy->getLength();

16
test/Transforms/MemCpyOpt/memset-memcpy-redundant-memset.ll
View File

@@ -100,6 +100,22 @@ define void @test_align_memcpy(i8* %src, i8* %dst, i64 %dst_size) {
ret void ret void
} }
; CHECK-LABEL: define void @test_non_i8_dst_type
; CHECK-NEXT: %dst = bitcast i64* %dst_pi64 to i8*
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %src_size, i32 1, i1 false)
; CHECK-DAG: [[DST:%[0-9]+]] = getelementptr i8, i8* %dst, i64 %src_size
; 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 %c, i64 [[SIZE]], i32 1, i1 false)
; CHECK-NEXT: ret void
define void @test_non_i8_dst_type(i8* %src, i64 %src_size, i64* %dst_pi64, i64 %dst_size, i8 %c) {
%dst = bitcast i64* %dst_pi64 to i8*
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_dst ; CHECK-LABEL: define void @test_different_dst
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %dst, i8 0, i64 %dst_size, i32 1, i1 false) ; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* %dst, i8 0, i64 %dst_size, i32 1, i1 false)
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst2, i8* %src, i64 %src_size, i32 1, i1 false) ; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst2, i8* %src, i64 %src_size, i32 1, i1 false)