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[SCEV] See through op.with.overflow intrinsics (re-apply)

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Summary:
This change teaches SCEV to see reduce `(extractvalue
0 (op.with.overflow X Y))` into `op X Y` (with a no-wrap tag if
possible).

This was first checked in at r265912 but reverted in r265950 because it
exposed some issues around how SCEV handled post-inc add recurrences.
Those issues have now been fixed.

Reviewers: atrick, regehr

Subscribers: mcrosier, mzolotukhin, llvm-commits

Differential Revision: http://reviews.llvm.org/D18684

llvm-svn: 271152
This commit is contained in:
Sanjoy Das
2016-05-29 00:34:42 +00:00
parent 7e4a64167d
commit f49ca52b9d
4 changed files with 425 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

54
llvm/lib/Analysis/ScalarEvolution.cpp
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@@ -3860,7 +3860,7 @@ struct BinaryOp {
/// Try to map \p V into a BinaryOp, and return \c None on failure.
static Optional<BinaryOp> MatchBinaryOp(Value *V) {
static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) {
auto *Op = dyn_cast<Operator>(V);
if (!Op)
return None;
@@ -3906,6 +3906,50 @@ static Optional<BinaryOp> MatchBinaryOp(Value *V) {
}
return BinaryOp(Op);
case Instruction::ExtractValue: {
auto *EVI = cast<ExtractValueInst>(Op);
if (EVI->getNumIndices() != 1 || EVI->getIndices()[0] != 0)
break;
auto *CI = dyn_cast<CallInst>(EVI->getAggregateOperand());
if (!CI)
break;
if (auto *F = CI->getCalledFunction())
switch (F->getIntrinsicID()) {
case Intrinsic::sadd_with_overflow:
case Intrinsic::uadd_with_overflow: {
if (!isOverflowIntrinsicNoWrap(cast<IntrinsicInst>(CI), DT))
return BinaryOp(Instruction::Add, CI->getArgOperand(0),
CI->getArgOperand(1));
// Now that we know that all uses of the arithmetic-result component of
// CI are guarded by the overflow check, we can go ahead and pretend
// that the arithmetic is non-overflowing.
if (F->getIntrinsicID() == Intrinsic::sadd_with_overflow)
return BinaryOp(Instruction::Add, CI->getArgOperand(0),
CI->getArgOperand(1), /* IsNSW = */ true,
/* IsNUW = */ false);
else
return BinaryOp(Instruction::Add, CI->getArgOperand(0),
CI->getArgOperand(1), /* IsNSW = */ false,
/* IsNUW*/ true);
}
case Intrinsic::ssub_with_overflow:
case Intrinsic::usub_with_overflow:
return BinaryOp(Instruction::Sub, CI->getArgOperand(0),
CI->getArgOperand(1));
case Intrinsic::smul_with_overflow:
case Intrinsic::umul_with_overflow:
return BinaryOp(Instruction::Mul, CI->getArgOperand(0),
CI->getArgOperand(1));
default:
break;
}
}
default:
break;
}
@@ -3980,7 +4024,7 @@ const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
if (auto BO = MatchBinaryOp(BEValueV)) {
if (auto BO = MatchBinaryOp(BEValueV, DT)) {
if (BO->Opcode == Instruction::Add && BO->LHS == PN) {
if (BO->IsNUW)
Flags = setFlags(Flags, SCEV::FlagNUW);
@@ -4956,7 +5000,7 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
return getUnknown(V);
Operator *U = cast<Operator>(V);
if (auto BO = MatchBinaryOp(U)) {
if (auto BO = MatchBinaryOp(U, DT)) {
switch (BO->Opcode) {
case Instruction::Add: {
// The simple thing to do would be to just call getSCEV on both operands
@@ -4997,7 +5041,7 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
else
AddOps.push_back(getSCEV(BO->RHS));
auto NewBO = MatchBinaryOp(BO->LHS);
auto NewBO = MatchBinaryOp(BO->LHS, DT);
if (!NewBO || (NewBO->Opcode != Instruction::Add &&
NewBO->Opcode != Instruction::Sub)) {
AddOps.push_back(getSCEV(BO->LHS));
@@ -5027,7 +5071,7 @@ const SCEV *ScalarEvolution::createSCEV(Value *V) {
}
MulOps.push_back(getSCEV(BO->RHS));
auto NewBO = MatchBinaryOp(BO->LHS);
auto NewBO = MatchBinaryOp(BO->LHS, DT);
if (!NewBO || NewBO->Opcode != Instruction::Mul) {
MulOps.push_back(getSCEV(BO->LHS));
break;