[PATCH] D21991: [libunwind][ARM] Improve unwinder stack usage - Make WMMX support optional

[Asiri Rathnayake via cfe-commits]

rmaprath added inline comments.

================
Comment at: CMakeLists.txt:108
@@ -107,2 +107,3 @@
 option(LIBUNWIND_ENABLE_CROSS_UNWINDING "Enable cross-platform unwinding support." OFF)
+option(LIBUNWIND_ENABLE_ARM_WMMX "Enable unwinding support for ARM WMMX registers." ON)
 
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rmaprath wrote:
> bcraig wrote:
> > Buried in one of the .s files, I see a preprocessor definition check for __ARM_WMMX.  Can the use of the preprocessor define be used instead of adding a new configuration option?
> Missed that. Digging into some past commits bumped into http://reviews.llvm.org/D5314#74501
> 
> I think it's safe to guard the whole thing with `__ARM_WMMX`. Will do that instead.
> 
> 
Although, now I'm not sure if clang ever generates this predefine.

The ACLE clearly says it should be defined for supporting targets: http://infocenter.arm.com/help/topic/com.arm.doc.ihi0053c/IHI0053C_acle_2_0.pdf

I'm not sure if that justifies using this predefine to completely exclude all of WMMX support. Perhaps a build option is safer? @jroelofs: what's your take?


http://reviews.llvm.org/D21991