[clang] [llvm] [AArch64] Add FEAT_FPAC to Grace (PR #133054)

[David Green via llvm-commits]

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@@ -1067,7 +1067,8 @@ def ProcessorFeatures {
                                      FeatureDotProd, FeatureFPARMv8, FeatureMatMulInt8,
                                      FeatureSSBS, FeatureCCIDX,
                                      FeatureJS, FeatureLSE, FeatureRAS, FeatureRCPC, FeatureRDM];
-  list<SubtargetFeature> Grace = !listconcat(NeoverseV2, [FeatureSVE2SM4, FeatureSVEAES, FeatureSVE2SHA3]);
+  list<SubtargetFeature> Grace = !listconcat(NeoverseV2, [FeatureSVE2SM4, FeatureSVEAES, FeatureSVE2SHA3,
+                                                          FeatureFPAC]);
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davemgreen wrote:

Yeah that sounds good - there are a number of other cores that have it but are not marked, but I don't have a list. The features was added after the cores were added and it didn't add them to all. Adding for V2 is a good start.

It can change the way PACBTI is emitted, I believe to make it more efficient and shouldn't be an issue so long as the instructions do throw exceptions.

https://github.com/llvm/llvm-project/pull/133054