[llvm] Apply the `AdjustICmpImmAndPred` optimization when it results in a one-instruction immediate materialization over a two-instruction materialization. (PR #83218)

[David Green via llvm-commits]

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@@ -658,9 +659,12 @@ tryAdjustICmpImmAndPred(Register RHS, CmpInst::Predicate P,
   // predicate if it is.
   if (Size == 32)
     C = static_cast<uint32_t>(C);
-  if (!isLegalArithImmed(C))
-    return std::nullopt;
-  return {{C, P}};
+  if (isLegalArithImmed(C))
+    return {{C, P}};
+  if (AArch64_AM::isLogicalImmediate(C, Size) &&
+      !AArch64_AM::isLogicalImmediate(OriginalC, Size))
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davemgreen wrote:

It would be a bit more code, but could this all use `AArch64_IMM::expandMOVImm(Imm, BitSize, Insn); Insn.size() == 1`? I believe that is what this is trying to achieve, and it would be more general to capture all the different ways for the immediate to be a single instruction.

https://github.com/llvm/llvm-project/pull/83218