In some cases Clang does not perform merging of instructions AND and TST (aka
ANDS xzr).
Example:
tst x2, x1
and x3, x2, x1
to:
ands x3, x2, x1
This patch add such merging during instruction selection: when AND is replaced
with ANDS instruction in LowerSELECT_CC, all users of AND also should be
changed for using this ANDS instruction
Short discussion on mailing list:
http://llvm.1065342.n5.nabble.com/llvm-dev-ARM-Peephole-optimization-instructions-tst-add-tp133109.html
Patch by Pavel Kosov.
Differential Revision: https://reviews.llvm.org/D71701
