On Fri, Aug 15, 2014 at 03:45:33PM +0400, Yuri Rumyantsev wrote:
> gcc/ChangeLog
> 2014-08-15 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.
--- config/i386/i386.md (revision 213842)
+++ config/i386/i386.md (working copy)
@@ -12111,7 +12111,13 @@
""
{
if (TARGET_BMI)
- return "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
+ {
+ if (ix86_avoid_false_dep_for_bm (insn, operands))
+ return "xor{<imodesuffix>}\t%0, %0\n\t"
+ "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
+ else
+ return "tzcnt{<imodesuffix>}\t{%1, %0|%0, %1}";
+ }
else if (optimize_function_for_size_p (cfun))
;
else if (TARGET_GENERIC)
etc., this will make lenght attribute incorrect though.
Jakub
