[PATCH] D71992: [ARM] Unrestrict Armv8 IT blocks

Mon Jan 13 14:58:20 PST 2020

efriedma added a comment.

Are there any cores where we don't want FeatureDontRestrictIT ?  I mean, multi-instruction it blocks were formally deprecated, but I'm not sure anyone actually took advantage of that.

I think we currently generate a warning in the assembler for deprecated it blocks? Do we want to eliminate that?

================
Comment at: llvm/lib/Target/ARM/ARMFeatures.h:77
 // there are some "conditionally deprecated" opcodes
   case ARM::tADDspr:
   case ARM::tBLXr:
----------------
The checks for tADDspr and tADDrSP look wrong; neither of those instructions are deprecated, as far as I can tell. Maybe it was confused with something else?  (I guess this isn't really part of you patch; feel free to ignore.)

Are these checks intentionally not controlled by the "Restricted" boolean?

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Comment at: llvm/lib/Target/ARM/ARMSubtarget.h:423
+  /// deprecated IT blocks, ignoring conformation to ARMv8 rule.
+  bool ForceNoRestrictIT = false;
+
----------------
Maybe worth noting in the comments that the "Force" booleans correspond to command-line options, not subtarget features?

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  https://reviews.llvm.org/D71992/new/

https://reviews.llvm.org/D71992