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indvars -disable-iv-rewrite: insert new trunc instructions carefully.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134112 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2011-06-29 23:03:57 +00:00
parent 3290239daf
commit cc359d9fa2
2 changed files with 52 additions and 15 deletions
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34
lib/Transforms/Scalar/IndVarSimplify.cpp
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@@ -609,8 +609,7 @@ protected:
const SCEVAddRecExpr *GetWideRecurrence(Instruction *NarrowUse);
Instruction *WidenIVUse(Instruction *NarrowUse,
Instruction *NarrowDef,
Instruction *WidenIVUse(Use &NarrowDefUse, Instruction *NarrowDef,
Instruction *WideDef);
};
} // anonymous namespace
@@ -724,9 +723,10 @@ static bool HoistStep(Instruction *IncV, Instruction *InsertPos,
/// WidenIVUse - Determine whether an individual user of the narrow IV can be
/// widened. If so, return the wide clone of the user.
Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
Instruction *NarrowDef,
Instruction *WidenIV::WidenIVUse(Use &NarrowDefUse, Instruction *NarrowDef,
Instruction *WideDef) {
Instruction *NarrowUse = cast<Instruction>(NarrowDefUse.getUser());
// To be consistent with IVUsers, stop traversing the def-use chain at
// inner-loop phis or post-loop phis.
if (isa<PHINode>(NarrowUse) && LI->getLoopFor(NarrowUse->getParent()) != L)
@@ -744,7 +744,7 @@ Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
unsigned IVWidth = SE->getTypeSizeInBits(WideType);
if (CastWidth < IVWidth) {
// The cast isn't as wide as the IV, so insert a Trunc.
IRBuilder<> Builder(NarrowUse);
IRBuilder<> Builder(NarrowDefUse);
NewDef = Builder.CreateTrunc(WideDef, NarrowUse->getType());
}
else {
@@ -778,11 +778,15 @@ Instruction *WidenIV::WidenIVUse(Instruction *NarrowUse,
// This user does not evaluate to a recurence after widening, so don't
// follow it. Instead insert a Trunc to kill off the original use,
// eventually isolating the original narrow IV so it can be removed.
IRBuilder<> Builder(NarrowUse);
IRBuilder<> Builder(NarrowDefUse);
Value *Trunc = Builder.CreateTrunc(WideDef, NarrowDef->getType());
NarrowUse->replaceUsesOfWith(NarrowDef, Trunc);
return 0;
}
// We assume that block terminators are not SCEVable.
assert(NarrowUse != NarrowUse->getParent()->getTerminator() &&
"can't split terminators");
// Reuse the IV increment that SCEVExpander created as long as it dominates
// NarrowUse.
Instruction *WideUse = 0;
@@ -876,20 +880,20 @@ PHINode *WidenIV::CreateWideIV(SCEVExpander &Rewriter) {
NarrowIVUsers.push_back(std::make_pair(&UI.getUse(), WidePhi));
}
while (!NarrowIVUsers.empty()) {
Use *NarrowDefUse;
Use *UsePtr;
Instruction *WideDef;
tie(NarrowDefUse, WideDef) = NarrowIVUsers.pop_back_val();
tie(UsePtr, WideDef) = NarrowIVUsers.pop_back_val();
Use &NarrowDefUse = *UsePtr;
// Process a def-use edge. This may replace the use, so don't hold a
// use_iterator across it.
Instruction *NarrowDef = cast<Instruction>(NarrowDefUse->get());
Instruction *NarrowUse = cast<Instruction>(NarrowDefUse->getUser());
Instruction *WideUse = WidenIVUse(NarrowUse, NarrowDef, WideDef);
Instruction *NarrowDef = cast<Instruction>(NarrowDefUse.get());
Instruction *WideUse = WidenIVUse(NarrowDefUse, NarrowDef, WideDef);
// Follow all def-use edges from the previous narrow use.
if (WideUse) {
for (Value::use_iterator UI = NarrowUse->use_begin(),
UE = NarrowUse->use_end(); UI != UE; ++UI) {
for (Value::use_iterator UI = NarrowDefUse.getUser()->use_begin(),
UE = NarrowDefUse.getUser()->use_end(); UI != UE; ++UI) {
NarrowIVUsers.push_back(std::make_pair(&UI.getUse(), WideUse));
}
}
@@ -1051,6 +1055,10 @@ bool IndVarSimplify::isSimpleIVUser(Instruction *I, const Loop *L) {
// Get the symbolic expression for this instruction.
const SCEV *S = SE->getSCEV(I);
// We assume that terminators are not SCEVable.
assert((!S || I != I->getParent()->getTerminator()) &&
"can't fold terminators");
// Only consider affine recurrences.
const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
if (AR && AR->getLoop() == L)