lebedev.ri updated this revision to Diff 310855.
lebedev.ri added a comment.
This revision is now accepted and ready to land.
Partial rebase (without updating test coverage)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D87188/new/
https://reviews.llvm.org/D87188
Files:
llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
Index: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1048,89 +1048,28 @@
return &Sel;
}
-/// There are many select variants for each of ABS/NABS.
-/// In matchSelectPattern(), there are different compare constants, compare
-/// predicates/operands and select operands.
-/// In isKnownNegation(), there are different formats of negated operands.
-/// Canonicalize all these variants to 1 pattern.
-/// This makes CSE more likely.
static Instruction *canonicalizeAbsNabs(SelectInst &Sel, ICmpInst &Cmp,
InstCombinerImpl &IC) {
if (!Cmp.hasOneUse() || !isa<Constant>(Cmp.getOperand(1)))
return nullptr;
- // Choose a sign-bit check for the compare (likely simpler for codegen).
- // ABS: (X <s 0) ? -X : X
- // NABS: (X <s 0) ? X : -X
Value *LHS, *RHS;
SelectPatternFlavor SPF = matchSelectPattern(&Sel, LHS, RHS).Flavor;
if (SPF != SelectPatternFlavor::SPF_ABS &&
SPF != SelectPatternFlavor::SPF_NABS)
return nullptr;
- Value *TVal = Sel.getTrueValue();
- Value *FVal = Sel.getFalseValue();
- assert(isKnownNegation(TVal, FVal) &&
- "Unexpected result from matchSelectPattern");
+ bool IntMinIsPoison = match(RHS, m_NSWNeg(m_Specific(LHS)));
+ Constant *IntMinIsPoisonC =
+ ConstantInt::get(Type::getInt1Ty(Sel.getContext()), IntMinIsPoison);
+ Instruction *Abs =
+ IC.Builder.CreateBinaryIntrinsic(Intrinsic::abs, LHS, IntMinIsPoisonC);
- // The compare may use the negated abs()/nabs() operand, or it may use
- // negation in non-canonical form such as: sub A, B.
- bool CmpUsesNegatedOp = match(Cmp.getOperand(0), m_Neg(m_Specific(TVal))) ||
- match(Cmp.getOperand(0), m_Neg(m_Specific(FVal)));
+ if (SPF == SelectPatternFlavor::SPF_NABS)
+ return IntMinIsPoison ? BinaryOperator::CreateNSWNeg(Abs)
+ : BinaryOperator::CreateNeg(Abs);
- bool CmpCanonicalized = !CmpUsesNegatedOp &&
- match(Cmp.getOperand(1), m_ZeroInt()) &&
- Cmp.getPredicate() == ICmpInst::ICMP_SLT;
- bool RHSCanonicalized = match(RHS, m_Neg(m_Specific(LHS)));
-
- // Is this already canonical?
- if (CmpCanonicalized && RHSCanonicalized)
- return nullptr;
-
- // If RHS is not canonical but is used by other instructions, don't
- // canonicalize it and potentially increase the instruction count.
- if (!RHSCanonicalized)
- if (!(RHS->hasOneUse() || (RHS->hasNUses(2) && CmpUsesNegatedOp)))
- return nullptr;
-
- // Create the canonical compare: icmp slt LHS 0.
- if (!CmpCanonicalized) {
- Cmp.setPredicate(ICmpInst::ICMP_SLT);
- Cmp.setOperand(1, ConstantInt::getNullValue(Cmp.getOperand(0)->getType()));
- if (CmpUsesNegatedOp)
- Cmp.setOperand(0, LHS);
- }
-
- // Create the canonical RHS: RHS = sub (0, LHS).
- if (!RHSCanonicalized) {
- assert(RHS->hasOneUse() && "RHS use number is not right");
- RHS = IC.Builder.CreateNeg(LHS);
- if (TVal == LHS) {
- // Replace false value.
- IC.replaceOperand(Sel, 2, RHS);
- FVal = RHS;
- } else {
- // Replace true value.
- IC.replaceOperand(Sel, 1, RHS);
- TVal = RHS;
- }
- }
-
- // If the select operands do not change, we're done.
- if (SPF == SelectPatternFlavor::SPF_NABS) {
- if (TVal == LHS)
- return &Sel;
- assert(FVal == LHS && "Unexpected results from matchSelectPattern");
- } else {
- if (FVal == LHS)
- return &Sel;
- assert(TVal == LHS && "Unexpected results from matchSelectPattern");
- }
-
- // We are swapping the select operands, so swap the metadata too.
- Sel.swapValues();
- Sel.swapProfMetadata();
- return &Sel;
+ return IC.replaceInstUsesWith(Sel, Abs);
}
/// If we have a select with an equality comparison, then we know the value in
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