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Reapply r121520, PartialAlias implementation for BasicAA, now that

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memdep is updated to handle it.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121725 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2010-12-13 22:50:24 +00:00
parent 2cd1952917
commit 0f7f194416
2 changed files with 38 additions and 2 deletions
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11
lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -857,6 +857,17 @@ BasicAliasAnalysis::aliasGEP(const GEPOperator *GEP1, uint64_t V1Size,
if (GEP1BaseOffset == 0 && GEP1VariableIndices.empty())
return MustAlias;
// If there is a difference betwen the pointers, but the difference is
// less than the size of the associated memory object, then we know
// that the objects are partially overlapping.
if (GEP1BaseOffset != 0 && GEP1VariableIndices.empty()) {
if (GEP1BaseOffset >= 0 ?
(V2Size != UnknownSize && (uint64_t)GEP1BaseOffset < V2Size) :
(V1Size != UnknownSize && -(uint64_t)GEP1BaseOffset < V1Size &&
GEP1BaseOffset != INT64_MIN))
return PartialAlias;
}
// If we have a known constant offset, see if this offset is larger than the
// access size being queried. If so, and if no variable indices can remove
// pieces of this constant, then we know we have a no-alias. For example,

29
test/Analysis/TypeBasedAliasAnalysis/precedence.ll
View File

@ -1,5 +1,5 @@
; RUN: opt -enable-tbaa -basicaa -tbaa -gvn -instcombine -S < %s | grep {ret i32 0}
; RUN: opt -enable-tbaa -tbaa -basicaa -gvn -instcombine -S < %s | grep {ret i32 1075000115}
; RUN: opt -enable-tbaa -basicaa -tbaa -gvn -instcombine -S < %s | FileCheck %s --check-prefix=TBAA
; RUN: opt -enable-tbaa -tbaa -basicaa -gvn -instcombine -S < %s | FileCheck %s --check-prefix=BASICAA
; According to the TBAA metadata the load and store don't alias. However,
; according to the actual code, they do. The order of the alias analysis
@ -7,6 +7,12 @@
target datalayout = "e-p:64:64:64"
; Test for simple MustAlias aliasing.
; TBAA: @trouble
; TBAA: ret i32 0
; BASICAA: @trouble
; BASICAA: ret i32 1075000115
define i32 @trouble(i32* %x) nounwind {
entry:
store i32 0, i32* %x, !tbaa !0
@ -16,6 +22,25 @@ entry:
ret i32 %tmp3
}
; Test for PartialAlias aliasing. GVN doesn't yet eliminate the load
; in the BasicAA case.
; TBAA: @offset
; TBAA: ret i64 0
; BASICAA: @offset
; BASICAA: ret i64 %tmp3
define i64 @offset(i64* %x) nounwind {
entry:
store i64 0, i64* %x, !tbaa !4
%0 = bitcast i64* %x to i8*
%1 = getelementptr i8* %0, i64 1
store i8 1, i8* %1, !tbaa !5
%tmp3 = load i64* %x, !tbaa !4
ret i64 %tmp3
}
!0 = metadata !{metadata !"int", metadata !1}
!1 = metadata !{metadata !"simple"}
!3 = metadata !{metadata !"float", metadata !1}
!4 = metadata !{metadata !"long", metadata !1}
!5 = metadata !{metadata !"small", metadata !1}