[PATCH] D24540: [AArch64] Add Cavium ThunderX subtarget support.

James Greenhalgh via llvm-commits llvm-commits at lists.llvm.org
Tue Oct 18 06:21:46 PDT 2016

jgreenhalgh added inline comments.

Comment at: lib/Target/AArch64/AArch64.td:267
+                                   FeaturePostRAScheduler,
+				   HasV8_1aOps]>;
jmolloy wrote:
> Indentation is off here.
I'm confused by this feature bit, and it doesn't line up with the -mcpu=thunderx support in GCC.

As far as I am aware, HasV8_1aOps enables support for all of the ARMv8.1-A extensions, i.e. the Large System Extensions, PAN, and the RDMA instructions. But, there exist ThunderX implementations which don't provide support for all of these extensions. For these ThunderX targets, the set of extensions enabled here would be too large.

The GCC implementation only enables ARMv8-A with the CRC, Advanced SIMD, Floating-Point and Cryptography extensions.

Would that be more correct here?



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