[SCEV] See through op.with.overflow intrinsics
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).
Reviewers: atrick, regehr
Subscribers: mcrosier, mzolotukhin, llvm-commits
Differential Revision: http://reviews.llvm.org/D18684
llvm-svn: 265912
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 654a766..6366e36 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -3831,7 +3831,7 @@
/// 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;
@@ -3877,6 +3877,50 @@
}
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;
}
@@ -3953,7 +3997,7 @@
// If the increment doesn't overflow, then neither the addrec nor
// the post-increment will overflow.
- 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);
@@ -4833,7 +4877,7 @@
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
@@ -4874,7 +4918,7 @@
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));
@@ -4904,7 +4948,7 @@
}
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;