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[AliasAnalysis] Take into account readonly attribute for the function arguments

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In getArgModRefInfo we consider all arguments as having MRI_ModRef.
However for arguments marked with readonly attribute we can return 
more precise answer - MRI_Ref.

Differential Revision: http://reviews.llvm.org/D13992

llvm-svn: 251525
This commit is contained in:
Igor Laevsky 2015-10-28 16:42:00 +00:00
parent 5d381bc775
commit 36e84c0fc7
2 changed files with 29 additions and 0 deletions
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3
llvm/lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -616,6 +616,9 @@ ModRefInfo BasicAAResult::getArgModRefInfo(ImmutableCallSite CS,
}
// FIXME: Handle memset_pattern4 and memset_pattern8 also.
if (CS.paramHasAttr(ArgIdx + 1, Attribute::ReadOnly))
return MRI_Ref;
return AAResultBase::getArgModRefInfo(CS, ArgIdx);
}

26
llvm/test/Analysis/BasicAA/modref.ll
View File

@ -190,6 +190,32 @@ define i32 @test10(i32* %P, i32* %P2) {
; CHECK: ret i32 %Diff
}
; CHECK-LABEL: @test11(
define i32 @test11(i32* %P, i32* %P2) {
%V1 = load i32, i32* %P
call i32 @func_argmemonly(i32* readonly %P2)
%V2 = load i32, i32* %P
%Diff = sub i32 %V1, %V2
ret i32 %Diff
; CHECK-NOT: load
; CHECK: ret i32 0
}
declare i32 @func_argmemonly_two_args(i32* %P, i32* %P2) argmemonly
; CHECK-LABEL: @test12(
define i32 @test12(i32* %P, i32* %P2, i32* %P3) {
%V1 = load i32, i32* %P
call i32 @func_argmemonly_two_args(i32* readonly %P2, i32* %P3)
%V2 = load i32, i32* %P
%Diff = sub i32 %V1, %V2
ret i32 %Diff
; CHECK: load
; CHECK: load
; CHECK: sub
; CHECK: ret i32 %Diff
}
declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind
declare void @llvm.memset.p0i8.i8(i8* nocapture, i8, i8, i32, i1) nounwind
declare void @llvm.memcpy.p0i8.p0i8.i8(i8* nocapture, i8* nocapture, i8, i32, i1) nounwind