tree fdc729a48243fcc998eadf9cbef7146c78efdacc
parent 1219711ceb48390669efdafb77a18f6d346d6bc8
author Hans Wennborg <hans@hanshq.net> 1516206550 +0000
committer Hans Wennborg <hans@hanshq.net> 1516206550 +0000

Merging r322313:
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r322313 | matze | 2018-01-11 13:57:03 -0800 (Thu, 11 Jan 2018) | 18 lines

PeepholeOptimizer: Do not form PHI with subreg arguments

When replacing a PHI the PeepholeOptimizer currently takes the register
class of the register at the first operand. This however is not correct
if this argument has a subregister index.

As there is currently no API to query the register class resulting from
applying a subregister index to all registers in a class, we can only
abort in these cases and not perform the transformation.

This changes findNextSource() to require the end of all copy chains to
not use a subregister if there is any PHI in the chain. I had to rewrite
the overly complicated inner loop there to have a good place to insert
the new check.

This fixes https://llvm.org/PR33071 (aka rdar://32262041)

Differential Revision: https://reviews.llvm.org/D40758
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llvm-svn: 322684