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Phi speculation improvement for BasicAA

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This is a partial solution to PR14351. It removes some of the special
significance of the first incoming phi value in the phi aliasing checking logic
in BasicAA. In the context of a loop, the old logic assumes that the first
incoming value is the interesting one (meaning that it is the one that comes
from outside the loop), but this is often not the case.  With this change, we
now test first the incoming value that comes from a block other than the parent
of the phi being tested.

llvm-svn: 168245
This commit is contained in:
Hal Finkel 2012-11-17 02:33:15 +00:00
parent 747188c9de
commit 9dc292f3c5
2 changed files with 83 additions and 3 deletions
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15
lib/Analysis/BasicAliasAnalysis.cpp
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@ -1065,9 +1065,15 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
if (PN > V2)
std::swap(Locs.first, Locs.second);
// Find the first incoming phi value not from its parent.
unsigned f = 0;
while (PN->getIncomingBlock(f) == PN->getParent() &&
f < PN->getNumIncomingValues()-1)
++f;
AliasResult Alias =
aliasCheck(PN->getIncomingValue(0), PNSize, PNTBAAInfo,
PN2->getIncomingValueForBlock(PN->getIncomingBlock(0)),
aliasCheck(PN->getIncomingValue(f), PNSize, PNTBAAInfo,
PN2->getIncomingValueForBlock(PN->getIncomingBlock(f)),
V2Size, V2TBAAInfo);
if (Alias == MayAlias)
return MayAlias;
@ -1096,7 +1102,10 @@ BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
ArePhisAssumedNoAlias = true;
}
for (unsigned i = 1, e = PN->getNumIncomingValues(); i != e; ++i) {
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
if (i == f)
continue;
AliasResult ThisAlias =
aliasCheck(PN->getIncomingValue(i), PNSize, PNTBAAInfo,
PN2->getIncomingValueForBlock(PN->getIncomingBlock(i)),

71
test/Analysis/BasicAA/phi-spec-order.ll Normal file
View File

@ -0,0 +1,71 @@
target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
target triple = "powerpc64-bgq-linux"
; RUN: opt < %s -basicaa -aa-eval -print-all-alias-modref-info -disable-output 2>&1 | FileCheck %s
@X = external global [16000 x double], align 32
@Y = external global [16000 x double], align 32
define signext i32 @s000() nounwind {
entry:
br label %for.cond2.preheader
for.cond2.preheader: ; preds = %for.end, %entry
%nl.018 = phi i32 [ 0, %entry ], [ %inc9, %for.end ]
br label %for.body4
for.body4: ; preds = %for.body4, %for.cond2.preheader
%lsr.iv4 = phi [16000 x double]* [ %i11, %for.body4 ], [ bitcast (double* getelementptr inbounds ([16000 x double]* @Y, i64 0, i64 8)
to [16000 x double]*), %for.cond2.preheader ]
%lsr.iv1 = phi [16000 x double]* [ %i10, %for.body4 ], [ @X, %for.cond2.preheader ]
; CHECK: NoAlias:{{[ \t]+}}[16000 x double]* %lsr.iv1, [16000 x double]* %lsr.iv4
%lsr.iv = phi i32 [ %lsr.iv.next, %for.body4 ], [ 16000, %for.cond2.preheader ]
%lsr.iv46 = bitcast [16000 x double]* %lsr.iv4 to <4 x double>*
%lsr.iv12 = bitcast [16000 x double]* %lsr.iv1 to <4 x double>*
%scevgep11 = getelementptr <4 x double>* %lsr.iv46, i64 -2
%i6 = load <4 x double>* %scevgep11, align 32, !tbaa !0
%add = fadd <4 x double> %i6, <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>
store <4 x double> %add, <4 x double>* %lsr.iv12, align 32, !tbaa !0
%scevgep10 = getelementptr <4 x double>* %lsr.iv46, i64 -1
%i7 = load <4 x double>* %scevgep10, align 32, !tbaa !0
%add.4 = fadd <4 x double> %i7, <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>
%scevgep9 = getelementptr <4 x double>* %lsr.iv12, i64 1
store <4 x double> %add.4, <4 x double>* %scevgep9, align 32, !tbaa !0
%i8 = load <4 x double>* %lsr.iv46, align 32, !tbaa !0
%add.8 = fadd <4 x double> %i8, <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>
%scevgep8 = getelementptr <4 x double>* %lsr.iv12, i64 2
store <4 x double> %add.8, <4 x double>* %scevgep8, align 32, !tbaa !0
%scevgep7 = getelementptr <4 x double>* %lsr.iv46, i64 1
%i9 = load <4 x double>* %scevgep7, align 32, !tbaa !0
%add.12 = fadd <4 x double> %i9, <double 1.000000e+00, double 1.000000e+00, double 1.000000e+00, double 1.000000e+00>
%scevgep3 = getelementptr <4 x double>* %lsr.iv12, i64 3
store <4 x double> %add.12, <4 x double>* %scevgep3, align 32, !tbaa !0
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep11, <4 x double>* %scevgep7
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep10, <4 x double>* %scevgep7
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep7, <4 x double>* %scevgep9
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep11, <4 x double>* %scevgep3
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep10, <4 x double>* %scevgep3
; CHECK: NoAlias:{{[ \t]+}}<4 x double>* %scevgep3, <4 x double>* %scevgep9
%lsr.iv.next = add i32 %lsr.iv, -16
%scevgep = getelementptr [16000 x double]* %lsr.iv1, i64 0, i64 16
%i10 = bitcast double* %scevgep to [16000 x double]*
%scevgep5 = getelementptr [16000 x double]* %lsr.iv4, i64 0, i64 16
%i11 = bitcast double* %scevgep5 to [16000 x double]*
%exitcond.15 = icmp eq i32 %lsr.iv.next, 0
br i1 %exitcond.15, label %for.end, label %for.body4
for.end: ; preds = %for.body4
%inc9 = add nsw i32 %nl.018, 1
%exitcond = icmp eq i32 %inc9, 400000
br i1 %exitcond, label %for.end10, label %for.cond2.preheader
for.end10: ; preds = %for.end
ret i32 0
}
!0 = metadata !{metadata !"double", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}