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 <ysrum...@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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