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Fix PR22179.

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We were incorrectly inferring nsw for certain SCEVs. We can be more
aggressive here (see Richard Smith's comment on
http://llvm.org/bugs/show_bug.cgi?id=22179) but this change just
focuses on correctness.

Differential Revision: http://reviews.llvm.org/D6914



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225591 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das
2015-01-10 23:41:24 +00:00
parent 3073d3960a
commit 7f0da20b97
4 changed files with 63 additions and 44 deletions
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lib/Analysis/ScalarEvolution.cpp
+33 -42
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@@ -1737,6 +1737,36 @@ namespace {
};
}
// We're trying to construct a SCEV of type `Type' with `Ops' as operands and
// `OldFlags' as can't-wrap behavior. Infer a more aggressive set of
// can't-overflow flags for the operation if possible.
static SCEV::NoWrapFlags
StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
const SmallVectorImpl<const SCEV *> &Ops,
SCEV::NoWrapFlags OldFlags) {
using namespace std::placeholders;
bool CanAnalyze =
Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr;
(void)CanAnalyze;
assert(CanAnalyze && "don't call from other places!");
int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
SCEV::NoWrapFlags SignOrUnsignWrap =
ScalarEvolution::maskFlags(OldFlags, SignOrUnsignMask);
// If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
auto IsKnownNonNegative =
std::bind(std::mem_fn(&ScalarEvolution::isKnownNonNegative), SE, _1);
if (SignOrUnsignWrap == SCEV::FlagNSW &&
std::all_of(Ops.begin(), Ops.end(), IsKnownNonNegative))
return ScalarEvolution::setFlags(OldFlags,
(SCEV::NoWrapFlags)SignOrUnsignMask);
return OldFlags;
}
/// getAddExpr - Get a canonical add expression, or something simpler if
/// possible.
const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
@@ -1752,20 +1782,7 @@ const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
"SCEVAddExpr operand types don't match!");
#endif
// If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
// And vice-versa.
int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
bool All = true;
for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
E = Ops.end(); I != E; ++I)
if (!isKnownNonNegative(*I)) {
All = false;
break;
}
if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
}
Flags = StrengthenNoWrapFlags(this, scAddExpr, Ops, Flags);
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops, LI);
@@ -2174,20 +2191,7 @@ const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
"SCEVMulExpr operand types don't match!");
#endif
// If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
// And vice-versa.
int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
bool All = true;
for (SmallVectorImpl<const SCEV *>::const_iterator I = Ops.begin(),
E = Ops.end(); I != E; ++I)
if (!isKnownNonNegative(*I)) {
All = false;
break;
}
if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
}
Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
// Sort by complexity, this groups all similar expression types together.
GroupByComplexity(Ops, LI);
@@ -2653,20 +2657,7 @@ ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
// meaningful BE count at this point (and if we don't, we'd be stuck
// with a SCEVCouldNotCompute as the cached BE count).
// If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
// And vice-versa.
int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
SCEV::NoWrapFlags SignOrUnsignWrap = maskFlags(Flags, SignOrUnsignMask);
if (SignOrUnsignWrap && (SignOrUnsignWrap != SignOrUnsignMask)) {
bool All = true;
for (SmallVectorImpl<const SCEV *>::const_iterator I = Operands.begin(),
E = Operands.end(); I != E; ++I)
if (!isKnownNonNegative(*I)) {
All = false;
break;
}
if (All) Flags = setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
}
Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags);
// Canonicalize nested AddRecs in by nesting them in order of loop depth.
if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {