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remove a pointless restriction from memcpyopt. It was

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refusing to optimize two memcpy's like this:

copy A <- B
copy C <- A

if it couldn't prove that noalias(B,C).  We can eliminate
the copy by producing a memmove instead of memcpy.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119694 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2010-11-18 08:00:57 +00:00
parent 7cac8e1691
commit 5a7aeaa019
3 changed files with 42 additions and 23 deletions
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11
lib/Transforms/Scalar/MemCpyOptimizer.cpp
View File

@ -688,11 +688,14 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
if (DepSize < MSize)
return false;
// Finally, we have to make sure that the dest of the second does not
// alias the source of the first.
Intrinsic::ID ResultFn = Intrinsic::memcpy;
// If the dest of the second might alias the source of the first, then the
// source and dest might overlap. We still want to eliminate the intermediate
// value, but we have to generate a memmove instead of memcpy.
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
if (!AA.isNoAlias(M->getRawDest(), MSize, MDep->getRawSource(), DepSize))
return false;
ResultFn = Intrinsic::memmove;
// If all checks passed, then we can transform these memcpy's
const Type *ArgTys[3] = {
@ -702,7 +705,7 @@ bool MemCpyOpt::processMemCpyMemCpyDependence(MemCpyInst *M, MemCpyInst *MDep,
};
Function *MemCpyFun =
Intrinsic::getDeclaration(M->getParent()->getParent()->getParent(),
M->getIntrinsicID(), ArgTys, 3);
ResultFn, ArgTys, 3);
// Make sure to use the lesser of the alignment of the source and the dest
// since we're changing where we're reading from, but don't want to increase

17
test/Transforms/MemCpyOpt/2008-04-29-SRetRemoval.ll
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@ -1,17 +0,0 @@
; RUN: opt < %s -memcpyopt -S | grep {call.*memcpy.*agg.result}
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin8"
@x = external global { x86_fp80, x86_fp80 } ; <{ x86_fp80, x86_fp80 }*> [#uses=1]
define void @foo({ x86_fp80, x86_fp80 }* noalias sret %agg.result) nounwind {
entry:
%x.0 = alloca { x86_fp80, x86_fp80 } ; <{ x86_fp80, x86_fp80 }*> [#uses=1]
%x.01 = bitcast { x86_fp80, x86_fp80 }* %x.0 to i8* ; <i8*> [#uses=2]
call void @llvm.memcpy.i32( i8* %x.01, i8* bitcast ({ x86_fp80, x86_fp80 }* @x to i8*), i32 32, i32 16 )
%agg.result2 = bitcast { x86_fp80, x86_fp80 }* %agg.result to i8* ; <i8*> [#uses=1]
call void @llvm.memcpy.i32( i8* %agg.result2, i8* %x.01, i32 32, i32 16 )
ret void
}
declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind

37
test/Transforms/MemCpyOpt/memcpy.ll
View File

@ -1,4 +1,4 @@
; RUN: opt < %s -basicaa -memcpyopt -dse -S | grep {call.*memcpy} | count 1
; RUN: opt < %s -basicaa -memcpyopt -dse -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i686-apple-darwin9"
@ -20,7 +20,7 @@ entry:
; CHECK: @test1
; CHECK: call void @ccoshl
; CHECK: call @llvm.memcpy
; CHECK: call void @llvm.memcpy
; CHECK-NOT: llvm.memcpy
; CHECK: ret void
ret void
@ -29,3 +29,36 @@ entry:
declare void @ccoshl({ x86_fp80, x86_fp80 }* sret , x86_fp80, x86_fp80) nounwind
declare void @llvm.memcpy.i32(i8*, i8*, i32, i32) nounwind
; The intermediate alloca and one of the memcpy's should be eliminated, the
; other should be related with a memmove.
define void @test2(i8* %P, i8* %Q) nounwind {
%memtmp = alloca { x86_fp80, x86_fp80 }, align 16
%R = bitcast { x86_fp80, x86_fp80 }* %memtmp to i8*
call void @llvm.memcpy.i32( i8* %R, i8* %P, i32 32, i32 16 )
call void @llvm.memcpy.i32( i8* %Q, i8* %R, i32 32, i32 16 )
ret void
; CHECK: @test2
; CHECK-NEXT: call void @llvm.memmove{{.*}}(i8* %Q, i8* %P
; CHECK-NEXT: ret void
}
@x = external global { x86_fp80, x86_fp80 }
define void @test3({ x86_fp80, x86_fp80 }* noalias sret %agg.result) nounwind {
%x.0 = alloca { x86_fp80, x86_fp80 }
%x.01 = bitcast { x86_fp80, x86_fp80 }* %x.0 to i8*
call void @llvm.memcpy.i32( i8* %x.01, i8* bitcast ({ x86_fp80, x86_fp80 }* @x to i8*), i32 32, i32 16 )
%agg.result2 = bitcast { x86_fp80, x86_fp80 }* %agg.result to i8*
call void @llvm.memcpy.i32( i8* %agg.result2, i8* %x.01, i32 32, i32 16 )
ret void
; CHECK: @test3
; CHECK-NEXT: %agg.result2 = bitcast
; CHECK-NEXT: call void @llvm.memcpy
; CHECK-NEXT: ret void
}