[InstSimplify] Remove redundant icmp+ptrtoint fold

[nikic]

There is a generic fold for recursively calling simplifyICmpInst with the ptrtoint cast stripped:

llvm-project/llvm/lib/Analysis/InstructionSimplify.cpp

Lines 3850 to 3867 in 9b6b52b

	// Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input
	// if the integer type is the same size as the pointer type.
	if (MaxRecurse && isa<PtrToIntInst>(LI) &&
	Q.DL.getTypeSizeInBits(SrcTy) == DstTy->getPrimitiveSizeInBits()) {
	if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
	// Transfer the cast to the constant.
	if (Value *V = simplifyICmpInst(Pred, SrcOp,
	ConstantExpr::getIntToPtr(RHSC, SrcTy),
	Q, MaxRecurse - 1))
	return V;
	} else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) {
	if (RI->getOperand(0)->getType() == SrcTy)
	// Compare without the cast.
	if (Value *V = simplifyICmpInst(Pred, SrcOp, RI->getOperand(0), Q,
	MaxRecurse - 1))
	return V;
	}
	}

As such, we shouldn't have to explicitly do this for the computePointerICmp() fold.

This is not strictly NFC because the recursion limit applies to the generic fold, though I wouldn't expect this to matter in practice.

[llvmbot]

@llvm/pr-subscribers-llvm-analysis

Author: Nikita Popov (nikic)

Changes

There is a generic fold for recursively calling simplifyICmpInst with the ptrtoint cast stripped:

llvm-project/llvm/lib/Analysis/InstructionSimplify.cpp

Lines 3850 to 3867 in 9b6b52b

	// Turn icmp (ptrtoint x), (ptrtoint/constant) into a compare of the input
	// if the integer type is the same size as the pointer type.
	if (MaxRecurse && isa<PtrToIntInst>(LI) &&
	Q.DL.getTypeSizeInBits(SrcTy) == DstTy->getPrimitiveSizeInBits()) {
	if (Constant *RHSC = dyn_cast<Constant>(RHS)) {
	// Transfer the cast to the constant.
	if (Value *V = simplifyICmpInst(Pred, SrcOp,
	ConstantExpr::getIntToPtr(RHSC, SrcTy),
	Q, MaxRecurse - 1))
	return V;
	} else if (PtrToIntInst *RI = dyn_cast<PtrToIntInst>(RHS)) {
	if (RI->getOperand(0)->getType() == SrcTy)
	// Compare without the cast.
	if (Value *V = simplifyICmpInst(Pred, SrcOp, RI->getOperand(0), Q,
	MaxRecurse - 1))
	return V;
	}
	}

As such, we shouldn't have to explicitly do this for the computePointerICmp() fold.

This is not strictly NFC because the recursion limit applies to the generic fold, though I wouldn't expect this to matter in practice.

---

Full diff: https://github.com/llvm/llvm-project/pull/171807.diff

1 Files Affected:

• (modified) llvm/lib/Analysis/InstructionSimplify.cpp (-8)

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 1d82515cd84f9..63930617071f3 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4077,14 +4077,6 @@ static Value *simplifyICmpInst(CmpPredicate Pred, Value *LHS, Value *RHS,
   if (LHS->getType()->isPointerTy())
     if (auto *C = computePointerICmp(Pred, LHS, RHS, Q))
       return C;
-  if (auto *CLHS = dyn_cast<PtrToIntOperator>(LHS))
-    if (auto *CRHS = dyn_cast<PtrToIntOperator>(RHS))
-      if (CLHS->getPointerOperandType() == CRHS->getPointerOperandType() &&
-          Q.DL.getTypeSizeInBits(CLHS->getPointerOperandType()) ==
-              Q.DL.getTypeSizeInBits(CLHS->getType()))
-        if (auto *C = computePointerICmp(Pred, CLHS->getPointerOperand(),
-                                         CRHS->getPointerOperand(), Q))
-          return C;
 
   // If the comparison is with the result of a select instruction, check whether
   // comparing with either branch of the select always yields the same value.

[nikic]

No changes on llvm-opt-benchmark.