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[PATCH PR62011]


Hi All,

Here is a fix for PR 62011 - remove false dependency for unary
bit-manipulation instructions for latest BigCore chips (Sandybridge
and Haswell) by outputting in assembly file zeroing destination
register before bmi instruction. I checked that performance restored
for popcnt, lzcnt and tzcnt instructions.

Bootstrap and regression testing did not show any new failures.

Is it OK for trunk?

gcc/ChangeLog
2014-08-14  Yuri Rumyantsev  <ysrumyan@gmail.com>

PR target/62011
* config/i386/i386-protos.h (ix86_avoid_false_dep_for_bm): New function
 prototype.
* config/i386/i386.c (ix86_avoid_false_dep_for_bm): New function.
* config/i386/i386.h (TARGET_AVOID_FALSE_DEP_FOR_BM) New macros.
* config/i386/i386.md (ctz<mode>2, clz<mode>2_lzcnt, popcount<mode>2,
 *popcount<mode>2_cmp, *popcountsi2_cmp_zext): Output zeroing
 destination register for unary bit-manipulation instructions
 if required.
* config/i386/x86-tune.def (X86_TUNE_AVOID_FALSE_DEP_FOR_BM): New.

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