From ea7915abb25a757a9814367baa4c81eff3304f87 Mon Sep 17 00:00:00 2001 From: Nikita Popov Date: Thu, 2 Oct 2025 14:46:42 +0200 Subject: [PATCH] [InstCombine] Remove foldSelectWithFrozenICmp() fold After https://github.com/llvm/llvm-project/pull/154336 this fold no longer triggers, as the freeze will be pushed through to the icmp operands, and generic handling will take care of it. --- .../InstCombine/InstCombineSelect.cpp | 29 ------------------- 1 file changed, 29 deletions(-) diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp index b6b3a95f35c76..87000a1c36eef 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp @@ -2934,32 +2934,6 @@ static Instruction *foldSelectWithSRem(SelectInst &SI, InstCombinerImpl &IC, return nullptr; } -static Value *foldSelectWithFrozenICmp(SelectInst &Sel, InstCombiner::BuilderTy &Builder) { - FreezeInst *FI = dyn_cast(Sel.getCondition()); - if (!FI) - return nullptr; - - Value *Cond = FI->getOperand(0); - Value *TrueVal = Sel.getTrueValue(), *FalseVal = Sel.getFalseValue(); - - // select (freeze(x == y)), x, y --> y - // select (freeze(x != y)), x, y --> x - // The freeze should be only used by this select. Otherwise, remaining uses of - // the freeze can observe a contradictory value. - // c = freeze(x == y) ; Let's assume that y = poison & x = 42; c is 0 or 1 - // a = select c, x, y ; - // f(a, c) ; f(poison, 1) cannot happen, but if a is folded - // ; to y, this can happen. - CmpPredicate Pred; - if (FI->hasOneUse() && - match(Cond, m_c_ICmp(Pred, m_Specific(TrueVal), m_Specific(FalseVal))) && - (Pred == ICmpInst::ICMP_EQ || Pred == ICmpInst::ICMP_NE)) { - return Pred == ICmpInst::ICMP_EQ ? FalseVal : TrueVal; - } - - return nullptr; -} - /// Given that \p CondVal is known to be \p CondIsTrue, try to simplify \p SI. static Value *simplifyNestedSelectsUsingImpliedCond(SelectInst &SI, Value *CondVal, @@ -4446,9 +4420,6 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) { if (Instruction *PN = foldSelectToPhi(SI, DT, Builder)) return replaceInstUsesWith(SI, PN); - if (Value *Fr = foldSelectWithFrozenICmp(SI, Builder)) - return replaceInstUsesWith(SI, Fr); - if (Value *V = foldRoundUpIntegerWithPow2Alignment(SI, Builder)) return replaceInstUsesWith(SI, V);