[InstCombine] add helper function for icmp+zext/sext; NFC
llvm-svn: 369421
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index dc6dcc3..b318d0b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4026,6 +4026,87 @@
return nullptr;
}
+static Instruction *foldICmpWithZextOrSext(ICmpInst &ICmp) {
+ assert(isa<CastInst>(ICmp.getOperand(0)) && "Expected cast for operand 0");
+ auto *CastOp0 = cast<CastInst>(ICmp.getOperand(0));
+ Value *X;
+ if (!match(CastOp0, m_ZExtOrSExt(m_Value(X))))
+ return nullptr;
+
+ bool IsSignedExt = CastOp0->getOpcode() == Instruction::SExt;
+ bool IsSignedCmp = ICmp.isSigned();
+ if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
+ // If the signedness of the two casts doesn't agree (i.e. one is a sext
+ // and the other is a zext), then we can't handle this.
+ if (CastOp0->getOpcode() != CastOp1->getOpcode())
+ return nullptr;
+
+ // Not an extension from the same type?
+ // TODO: Handle this by extending the narrower operand to the type of
+ // the wider operand.
+ Value *Y = CastOp1->getOperand(0);
+ if (X->getType() != Y->getType())
+ return nullptr;
+
+ // (zext X) == (zext Y) --> X == Y
+ // (sext X) == (sext Y) --> X == Y
+ if (ICmp.isEquality())
+ return new ICmpInst(ICmp.getPredicate(), X, Y);
+
+ // A signed comparison of sign extended values simplifies into a
+ // signed comparison.
+ if (IsSignedCmp && IsSignedExt)
+ return new ICmpInst(ICmp.getPredicate(), X, Y);
+
+ // The other three cases all fold into an unsigned comparison.
+ return new ICmpInst(ICmp.getUnsignedPredicate(), X, Y);
+ }
+
+ // Below here, we are only folding a compare with constant.
+ auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
+ if (!C)
+ return nullptr;
+
+ // Compute the constant that would happen if we truncated to SrcTy then
+ // re-extended to DestTy.
+ Type *SrcTy = CastOp0->getSrcTy();
+ Type *DestTy = CastOp0->getDestTy();
+ Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
+ Constant *Res2 = ConstantExpr::getCast(CastOp0->getOpcode(), Res1, DestTy);
+
+ // If the re-extended constant didn't change...
+ if (Res2 == C) {
+ if (ICmp.isEquality())
+ return new ICmpInst(ICmp.getPredicate(), X, Res1);
+
+ // A signed comparison of sign extended values simplifies into a
+ // signed comparison.
+ if (IsSignedExt && IsSignedCmp)
+ return new ICmpInst(ICmp.getPredicate(), X, Res1);
+
+ // The other three cases all fold into an unsigned comparison.
+ return new ICmpInst(ICmp.getUnsignedPredicate(), X, Res1);
+ }
+
+ // The re-extended constant changed, partly changed (in the case of a vector),
+ // or could not be determined to be equal (in the case of a constant
+ // expression), so the constant cannot be represented in the shorter type.
+ // All the cases that fold to true or false will have already been handled
+ // by SimplifyICmpInst, so only deal with the tricky case.
+ if (IsSignedCmp || !IsSignedExt || !isa<ConstantInt>(C))
+ return nullptr;
+
+ // Is source op positive?
+ // icmp ult (sext X), C --> icmp sgt X, -1
+ if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
+ return new ICmpInst(CmpInst::ICMP_SGT, X, Constant::getAllOnesValue(SrcTy));
+
+ // Is source op negative?
+ // icmp ugt (sext X), C --> icmp slt X, 0
+ assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
+ return new ICmpInst(CmpInst::ICMP_SLT, X, Constant::getNullValue(SrcTy));
+}
+
/// Handle icmp (cast x), (cast or constant).
Instruction *InstCombiner::foldICmpWithCastOp(ICmpInst &ICmp) {
auto *CastOp0 = dyn_cast<CastInst>(ICmp.getOperand(0));
@@ -4067,82 +4148,7 @@
return new ICmpInst(ICmp.getPredicate(), Op0Src, NewOp1);
}
- // The code below only handles extension cast instructions, so far.
- // Enforce this.
- if (CastOp0->getOpcode() != Instruction::ZExt &&
- CastOp0->getOpcode() != Instruction::SExt)
- return nullptr;
-
- bool isSignedExt = CastOp0->getOpcode() == Instruction::SExt;
- bool isSignedCmp = ICmp.isSigned();
-
- if (auto *CastOp1 = dyn_cast<CastInst>(ICmp.getOperand(1))) {
- // Not an extension from the same type?
- Value *Op1Src = CastOp1->getOperand(0);
- if (Op1Src->getType() != Op0Src->getType())
- return nullptr;
-
- // If the signedness of the two casts doesn't agree (i.e. one is a sext
- // and the other is a zext), then we can't handle this.
- if (CastOp1->getOpcode() != CastOp0->getOpcode())
- return nullptr;
-
- // Deal with equality cases early.
- if (ICmp.isEquality())
- return new ICmpInst(ICmp.getPredicate(), Op0Src, Op1Src);
-
- // A signed comparison of sign extended values simplifies into a
- // signed comparison.
- if (isSignedCmp && isSignedExt)
- return new ICmpInst(ICmp.getPredicate(), Op0Src, Op1Src);
-
- // The other three cases all fold into an unsigned comparison.
- return new ICmpInst(ICmp.getUnsignedPredicate(), Op0Src, Op1Src);
- }
-
- // If we aren't dealing with a constant on the RHS, exit early.
- auto *C = dyn_cast<Constant>(ICmp.getOperand(1));
- if (!C)
- return nullptr;
-
- // Compute the constant that would happen if we truncated to SrcTy then
- // re-extended to DestTy.
- Constant *Res1 = ConstantExpr::getTrunc(C, SrcTy);
- Constant *Res2 = ConstantExpr::getCast(CastOp0->getOpcode(), Res1, DestTy);
-
- // If the re-extended constant didn't change...
- if (Res2 == C) {
- // Deal with equality cases early.
- if (ICmp.isEquality())
- return new ICmpInst(ICmp.getPredicate(), Op0Src, Res1);
-
- // A signed comparison of sign extended values simplifies into a
- // signed comparison.
- if (isSignedExt && isSignedCmp)
- return new ICmpInst(ICmp.getPredicate(), Op0Src, Res1);
-
- // The other three cases all fold into an unsigned comparison.
- return new ICmpInst(ICmp.getUnsignedPredicate(), Op0Src, Res1);
- }
-
- // The re-extended constant changed, partly changed (in the case of a vector),
- // or could not be determined to be equal (in the case of a constant
- // expression), so the constant cannot be represented in the shorter type.
- // All the cases that fold to true or false will have already been handled
- // by SimplifyICmpInst, so only deal with the tricky case.
- if (isSignedCmp || !isSignedExt || !isa<ConstantInt>(C))
- return nullptr;
-
- // Is source op positive?
- // icmp ult (sext X), C --> icmp sgt X, -1
- if (ICmp.getPredicate() == ICmpInst::ICMP_ULT)
- return new ICmpInst(CmpInst::ICMP_SGT, Op0Src,
- Constant::getAllOnesValue(SrcTy));
-
- // Is source op negative?
- // icmp ugt (sext X), C --> icmp slt X, 0
- assert(ICmp.getPredicate() == ICmpInst::ICMP_UGT && "ICmp should be folded!");
- return new ICmpInst(CmpInst::ICMP_SLT, Op0Src, Constant::getNullValue(SrcTy));
+ return foldICmpWithZextOrSext(ICmp);
}
static bool isNeutralValue(Instruction::BinaryOps BinaryOp, Value *RHS) {