[llvm] [AMDGPU] Use std::optional in InstCombine of amdgcn_fmed3. NFC. (PR #108223)

[Shilei Tian via llvm-commits]

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@@ -353,23 +353,20 @@ bool GCNTTIImpl::canSimplifyLegacyMulToMul(const Instruction &I,
 }
 
 /// Match an fpext from half to float, or a constant we can convert.
-static bool matchFPExtFromF16(Value *Arg, Value *&FPExtSrc) {
-  if (match(Arg, m_OneUse(m_FPExt(m_Value(FPExtSrc)))))
-    return FPExtSrc->getType()->isHalfTy();
-
+static std::optional<Value *> matchFPExtFromF16(Value *Arg) {
+  Value *Src;
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shiltian wrote:

I understand here you just follow existing code, but I'd just initialize them to `nullptr`.

https://github.com/llvm/llvm-project/pull/108223