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Implement AccessesArguments checking in the two-callsite form

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of BasicAA::getModRefInfo. This allows BasicAA to say that two
memset calls to non-aliasing memory locations don't interfere.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110393 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-08-05 23:34:50 +00:00
parent 0c3f3358df
commit 130073904f
2 changed files with 47 additions and 3 deletions
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34
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -429,13 +429,43 @@ BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
if (CS1B == OnlyReadsMemory && CS2B == OnlyReadsMemory)
return NoModRef;
AliasAnalysis::ModRefResult Mask = ModRef;
// If CS1 only reads memory, the only dependence on CS2 can be
// from CS1 reading memory written by CS2.
if (CS1B == OnlyReadsMemory)
return Ref;
Mask = ModRefResult(Mask & Ref);
// If CS2 only access memory through arguments, accumulate the mod/ref
// information from CS1's references to the memory referenced by
// CS2's arguments.
if (CS2B == AccessesArguments) {
AliasAnalysis::ModRefResult R = NoModRef;
for (ImmutableCallSite::arg_iterator
I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
R = ModRefResult((R | getModRefInfo(CS1, *I, UnknownSize)) & Mask);
if (R == Mask)
break;
}
return R;
}
// If CS1 only accesses memory through arguments, check if CS2 references
// any of the memory referenced by CS1's arguments. If not, return NoModRef.
if (CS1B == AccessesArguments) {
AliasAnalysis::ModRefResult R = NoModRef;
for (ImmutableCallSite::arg_iterator
I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I)
if (getModRefInfo(CS2, *I, UnknownSize) != NoModRef) {
R = Mask;
break;
}
if (R == NoModRef)
return R;
}
// Otherwise, fall back to NoAA (mod+ref).
return NoAA::getModRefInfo(CS1, CS2);
return ModRefResult(NoAA::getModRefInfo(CS1, CS2) & Mask);
}
/// GetIndexDifference - Dest and Src are the variable indices from two

16
test/Analysis/BasicAA/getmodrefinfo-cs-cs.ll
View File

@ -1,12 +1,26 @@
; RUN: opt < %s -aa-eval -print-all-alias-modref-info -disable-output |& FileCheck %s
; CHECK: Just Ref: call void @ro() <-> call void @f0()
declare void @f0()
declare void @ro() readonly
define void @test() {
define void @test0() {
call void @f0()
call void @ro()
ret void
}
; CHECK: NoModRef: call void @llvm.memset.p0i8.i64(i8* @A, i8 0, i64 1, i32 1, i1 false) <-> call void @llvm.memset.p0i8.i64(i8* @B, i8 0, i64 1, i32 1, i1 false)
; CHECK: NoModRef: call void @llvm.memset.p0i8.i64(i8* @B, i8 0, i64 1, i32 1, i1 false) <-> call void @llvm.memset.p0i8.i64(i8* @A, i8 0, i64 1, i32 1, i1 false)
declare void @llvm.memset.i64(i8*, i8, i64, i32)
@A = external global i8
@B = external global i8
define void @test1() {
call void @llvm.memset.i64(i8* @A, i8 0, i64 1, i32 1)
call void @llvm.memset.i64(i8* @B, i8 0, i64 1, i32 1)
ret void
}