Backport: fma3 instruction generation for 'march=native' in AMD processors
Gopalasubramanian, Ganesh
Ganesh.Gopalasubramanian@amd.com
Wed May 9 10:26:00 GMT 2012
Hello,
Below is the patch that has been committed in trunk (Revision: 187075).
We like to backport it to GCC 4.7 branch as couple of AMD processors require this change for fma3 instruction generation.
Bootstrapping and testing are successful.
Is it OK to commit in GCC 4.7 branch?
Regards
Ganesh
PATCH
=====
* config/i386/driver-i386.c (host_detect_local_cpu): Reset
has_fma4 for AMD processors with both fma3 and fma4 support.
Index: config/i386/driver-i386.c
===================================================================
--- config/i386/driver-i386.c (revision 186897)
+++ config/i386/driver-i386.c (working copy)
@@ -472,6 +472,8 @@
has_abm = ecx & bit_ABM;
has_lwp = ecx & bit_LWP;
has_fma4 = ecx & bit_FMA4;
+ if (vendor == SIG_AMD && has_fma4 && has_fma)
+ has_fma4 = 0;
has_xop = ecx & bit_XOP;
has_tbm = ecx & bit_TBM;
has_lzcnt = ecx & bit_LZCNT;
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