[llvm] [InstCombine] Make `(binop ({s|u}itofp),({s|u}itofp))` transform more flexible to mismatched signs (PR #84389)

[Nikita Popov via llvm-commits]

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@@ -1406,57 +1406,48 @@ Value *InstCombinerImpl::dyn_castNegVal(Value *V) const {
 //        -> ({s|u}itofp (int_binop x, y))
 //    2) (fp_binop ({s|u}itofp x), FpC)
 //        -> ({s|u}itofp (int_binop x, (fpto{s|u}i FpC)))
-Instruction *InstCombinerImpl::foldFBinOpOfIntCasts(BinaryOperator &BO) {
-  Value *IntOps[2] = {nullptr, nullptr};
-  Constant *Op1FpC = nullptr;
-
-  // Check for:
-  //    1) (binop ({s|u}itofp x), ({s|u}itofp y))
-  //    2) (binop ({s|u}itofp x), FpC)
-  if (!match(BO.getOperand(0), m_SIToFP(m_Value(IntOps[0]))) &&
-      !match(BO.getOperand(0), m_UIToFP(m_Value(IntOps[0]))))
-    return nullptr;
-
-  if (!match(BO.getOperand(1), m_Constant(Op1FpC)) &&
-      !match(BO.getOperand(1), m_SIToFP(m_Value(IntOps[1]))) &&
-      !match(BO.getOperand(1), m_UIToFP(m_Value(IntOps[1]))))
-    return nullptr;
+//
+// Assuming the sign of the cast for x/y is `OpsFromSigned`.
+Instruction *InstCombinerImpl::foldFBinOpOfIntCastsFromSign(
+    BinaryOperator &BO, bool OpsFromSigned, SmallVector<Value *, 2> IntOps,
+    Constant *Op1FpC, SmallVectorImpl<WithCache<const Value *>> *OpsKnown) {
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nikic wrote:

Definitely prefer the reference. Also, why is this passing IntOps by value?

You might also want to replace the `SmallVector<Value *, 2>` with `std::array<Value *, 2>` here.

https://github.com/llvm/llvm-project/pull/84389