================
@@ -1898,6 +1882,55 @@ static Instruction *foldSelectICmpEq(SelectInst &SI,
ICmpInst *ICI,
return nullptr;
}
+// Turn select (Cmp X C1) (BOp X C2) C3
+// -> BOp (min/max X C1) C2
+// iff C3 == BOp C1 C2
+// Fold `select` with a const operand to a binary operation.
+// This allows for better canonicalization.
+static Value *foldSelectWithConstOpToBinOp(ICmpInst *Cmp, Value *TrueVal,
+ Value *FalseVal,
+ IRBuilderBase &Builder) {
+ BinaryOperator *BOp;
+ Constant *C1, *C2, *C3;
+ Value *X, *NewTrue, *NewFalse;
+ ICmpInst::Predicate Predicate;
+
+ if (!match(Cmp, m_ICmp(Predicate, m_Value(X), m_Constant(C1))))
+ return nullptr;
+
+ if (match(TrueVal, m_Constant())) {
+ std::swap(FalseVal, TrueVal);
+ NewTrue = C1;
+ NewFalse = X;
+ } else {
+ NewTrue = X;
+ NewFalse = C1;
+ }
+
+ if (!match(TrueVal, m_BinOp(BOp)) || !match(FalseVal, m_Constant(C3)))
+ return nullptr;
+
+ if (!match(BOp, m_OneUse(m_c_BinOp(m_Specific(X), m_Constant(C2)))))
+ return nullptr;
+
+ // `select (Cmp X C1) (sub C2 X) (sub C1 C2)` cannot be transformed
+ // into something like `sub (select (Cmp X C1) X C1) C2`
+ if (!BOp->isCommutative() && BOp->getOperand(0) != X)
+ return nullptr;
----------------
dtcxzyw wrote:
```suggestion
if (!match(BOp, m_OneUse(m_BinOp(m_Specific(X), m_Constant(C2)))))
return nullptr;
```
It is unnecessary to use `m_c_BinOp` if you don't want to handle `sub C, X`
cases.
https://github.com/llvm/llvm-project/pull/116888
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