Stanislav Mekhanoshin 3197eb6981 [AMDGPU] Optimize SI_IF lowering for simple if regions ...

Currently SI_IF results in a s_and_saveexec_b64 followed by s_xor_b64.
The xor is used to extract only the changed bits. In case of a simple
if region where the only use of that value is in the SI_END_CF to
restore the old exec mask, we can omit the xor and perform an or of
the exec mask with the original exec value saved by the
s_and_saveexec_b64.

Differential Revision: https://reviews.llvm.org/D35861

llvm-svn: 309185

2017-07-26 21:29:15 +00:00

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