[llvm] [TTI][TLI] Support scalable immediates with isLegalAddImmediate (PR #84173)

[David Green via llvm-commits]

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@@ -16595,6 +16595,21 @@ bool AArch64TargetLowering::isLegalAddImmediate(int64_t Immed) const {
   return IsLegal;
 }
 
+bool AArch64TargetLowering::isLegalAddScalableImmediate(int64_t Imm) const {
+  // Scalable immediates require SVE support.
+  if (!Subtarget->hasSVE())
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davemgreen wrote:

Should all of this require sve2? Otherwise we don't generate the instructions.

https://github.com/llvm/llvm-project/pull/84173