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[DependenceAnalysis] Fix for PR21585: collectUpperBound triggers asserts

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collectUpperBound hits an assertion when the back edge count is wider then the desired type.

If that happens, truncate the backedge count.

Patch by Philip Pfaffe!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237439 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
James Molloy 2015-05-15 12:17:22 +00:00
parent 039eb5a7b8
commit 39a7d6e91d
2 changed files with 125 additions and 2 deletions
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22
lib/Analysis/DependenceAnalysis.cpp
View File

@ -830,6 +830,14 @@ bool DependenceAnalysis::checkSrcSubscript(const SCEV *Src,
return isLoopInvariant(Src, LoopNest);
const SCEV *Start = AddRec->getStart();
const SCEV *Step = AddRec->getStepRecurrence(*SE);
const SCEV *UB = SE->getBackedgeTakenCount(AddRec->getLoop());
if (!isa<SCEVCouldNotCompute>(UB)) {
if (SE->getTypeSizeInBits(Start->getType()) <
SE->getTypeSizeInBits(UB->getType())) {
if (!AddRec->getNoWrapFlags())
return false;
}
}
if (!isLoopInvariant(Step, LoopNest))
return false;
Loops.set(mapSrcLoop(AddRec->getLoop()));
@ -848,6 +856,14 @@ bool DependenceAnalysis::checkDstSubscript(const SCEV *Dst,
return isLoopInvariant(Dst, LoopNest);
const SCEV *Start = AddRec->getStart();
const SCEV *Step = AddRec->getStepRecurrence(*SE);
const SCEV *UB = SE->getBackedgeTakenCount(AddRec->getLoop());
if (!isa<SCEVCouldNotCompute>(UB)) {
if (SE->getTypeSizeInBits(Start->getType()) <
SE->getTypeSizeInBits(UB->getType())) {
if (!AddRec->getNoWrapFlags())
return false;
}
}
if (!isLoopInvariant(Step, LoopNest))
return false;
Loops.set(mapDstLoop(AddRec->getLoop()));
@ -942,13 +958,15 @@ bool DependenceAnalysis::isKnownPredicate(ICmpInst::Predicate Pred,
// All subscripts are all the same type.
// Loop bound may be smaller (e.g., a char).
// Should zero extend loop bound, since it's always >= 0.
// This routine collects upper bound and extends if needed.
// This routine collects upper bound and extends or truncates if needed.
// Truncating is safe when subscripts are known not to wrap. Cases without
// nowrap flags should have been rejected earlier.
// Return null if no bound available.
const SCEV *DependenceAnalysis::collectUpperBound(const Loop *L,
Type *T) const {
if (SE->hasLoopInvariantBackedgeTakenCount(L)) {
const SCEV *UB = SE->getBackedgeTakenCount(L);
return SE->getNoopOrZeroExtend(UB, T);
return SE->getTruncateOrZeroExtend(UB, T);
}
return nullptr;
}

105
test/Analysis/DependenceAnalysis/PR21585.ll Normal file
View File

@ -0,0 +1,105 @@
; RUN: opt < %s -analyze -basicaa -globalsmodref-aa -da | FileCheck %s
define void @i32_subscript(i32* %a) {
entry:
br label %for.body
for.body:
%i = phi i32 [ 0, %entry ], [ %i.inc, %for.body ]
%a.addr = getelementptr i32, i32* %a, i32 %i
%a.addr.2 = getelementptr i32, i32* %a, i32 5
%0 = load i32, i32* %a.addr, align 4
%1 = add i32 %0, 1
store i32 %1, i32* %a.addr.2, align 4
%i.inc = add nsw i32 %i, 1
%i.inc.ext = sext i32 %i to i64
%exitcond = icmp ne i64 %i.inc.ext, 100
br i1 %exitcond, label %for.body, label %for.end
for.end:
ret void
}
; CHECK: none
; CHECK: anti
; CHECK: output
; Test for a bug, which caused an assert in ScalarEvolution because
; the Dependence Analyzer attempted to zero extend a type to a smaller
; type.
; void t(unsigned int *a, unsigned int n) {
; for (unsigned int i = 0; i != n; i++) {
; a[(unsigned short)i] = g;
; }}
@g = common global i32 0, align 4
define void @t(i32* noalias %a, i32 %n) nounwind {
entry:
%cmp1 = icmp eq i32 %n, 0
br i1 %cmp1, label %for.end, label %for.body
for.body:
%i.02 = phi i32 [ %inc, %for.body ], [ 0, %entry ]
%0 = load i32, i32* @g, align 4
%idxprom = and i32 %i.02, 65535
%arrayidx = getelementptr inbounds i32, i32* %a, i32 %idxprom
store i32 %0, i32* %arrayidx, align 4
%inc = add i32 %i.02, 1
%cmp = icmp eq i32 %inc, %n
br i1 %cmp, label %for.end, label %for.body
for.end:
ret void
}
; CHECK: input
; CHECK: none
; CHECK: output
define void @i16_wrap(i64* %a) {
entry:
br label %for.body
for.body:
%i = phi i64 [0, %entry], [%i.inc, %for.inc]
%i.tr = trunc i64 %i to i16
%idx = getelementptr i64, i64* %a, i16 %i.tr
%0 = load i64, i64* %idx
%1 = add i64 %0, 1
store i64 %1, i64* %idx
br label %for.inc
for.inc:
%i.inc = add nuw i64 %i, 1
%cmp = icmp ult i64 %i.inc, 17179869184
br i1 %cmp, label %for.body, label %for.end
for.end:
ret void
}
; CHECK: input
; CHECK: anti
; CHECK: output
define void @i8_stride_wrap(i32* noalias %a, i32* noalias %b) {
entry:
br label %for.body
for.body:
%i = phi i32 [1,%entry], [%i.inc, %for.inc]
%i.tr = trunc i32 %i to i8
%idx = getelementptr i32, i32* %a, i8 %i.tr
%idx.2 = getelementptr i32, i32* %b, i32 %i
%0 = load i32, i32* %idx, align 4
%1 = add i32 %0, 1
store i32 %1, i32* %idx.2, align 4
br label %for.inc
for.inc:
%i.inc = add nsw i32 %i, 256
%exitcond = icmp ult i32 %i, 65536
br i1 %exitcond, label %for.body, label %for.end
for.end:
ret void
}
; CHECK: input
; CHECK: none
; CHECK: none