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enhance basicaa to return "Mod" for a memcpy call when the 

queried location doesn't overlap the source, and add a testcase.

llvm-svn: 120370
This commit is contained in:
Chris Lattner 2010-11-30 00:43:16 +00:00
parent 62718de2b9
commit 90c4947df7
2 changed files with 18 additions and 2 deletions
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5
llvm/lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -687,10 +687,15 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
Len = LenCI->getZExtValue();
Value *Dest = II->getArgOperand(0);
Value *Src = II->getArgOperand(1);
// If it can't overlap the source dest, then it doesn't modref the loc.
if (isNoAlias(Location(Dest, Len), Loc)) {
if (isNoAlias(Location(Src, Len), Loc))
return NoModRef;
// If it can't overlap the dest, then worst case it reads the loc.
Min = Ref;
} else if (isNoAlias(Location(Src, Len), Loc)) {
// If it can't overlap the source, then worst case it mutates the loc.
Min = Mod;
}
break;
}

15
llvm/test/Transforms/DeadStoreElimination/simple.ll
View File

@ -55,16 +55,27 @@ define void @test5(i32* %Q) {
; CHECK-NEXT: ret void
}
declare void @llvm.memset.i32(i8*, i8, i32, i32)
declare void @llvm.memset.i64(i8*, i8, i64, i32)
declare void @llvm.memcpy.i64(i8*, i8*, i64, i32)
; Should delete store of 10 even though memset is a may-store to P (P and Q may
; alias).
define void @test6(i32 *%p, i8 *%q) {
store i32 10, i32* %p, align 4 ;; dead.
call void @llvm.memset.i32(i8* %q, i8 42, i32 900, i32 1)
call void @llvm.memset.i64(i8* %q, i8 42, i64 900, i32 1)
store i32 30, i32* %p, align 4
ret void
; CHECK: @test6
; CHECK-NEXT: call void @llvm.memset
}
; Should delete store of 10 even though memcpy is a may-store to P (P and Q may
; alias).
define void @test7(i32 *%p, i8 *%q, i8* noalias %r) {
store i32 10, i32* %p, align 4 ;; dead.
call void @llvm.memcpy.i64(i8* %q, i8* %r, i64 900, i32 1)
store i32 30, i32* %p, align 4
ret void
; CHECK: @test7
; CHECK-NEXT: call void @llvm.memcpy
}