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[Bug target/58450] -fno-trapping-math causes decrease in performance
- From: "hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Tue, 17 Sep 2013 21:33:18 +0000
- Subject: [Bug target/58450] -fno-trapping-math causes decrease in performance
- Auto-submitted: auto-generated
- References: <bug-58450-4 at http dot gcc dot gnu dot org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58450
H.J. Lu <hjl.tools at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |WAITING
Last reconfirmed| |2013-09-17
CC| |hjl.tools at gmail dot com
Ever confirmed|0 |1
--- Comment #2 from H.J. Lu <hjl.tools at gmail dot com> ---
This is related to PR 57988. Without -fno-trapping-math, there are
0x00000000004009b6 <+54>: cvtsi2sd %rdx,%xmm2
0x00000000004009bb <+59>: je 0x400998 <_Z6pi_apxv+24>
0x00000000004009bd <+61>: movapd %xmm1,%xmm4
0x00000000004009c1 <+65>: add $0x1,%rax
0x00000000004009c5 <+69>: add $0x2,%rdx
0x00000000004009c9 <+73>: cmp $0x5f5e100,%rax
0x00000000004009cf <+79>: divsd %xmm2,%xmm4
It hides the latency of cvtsi2sd %rdx,%xmm2 due to partial SSE register
stall. Please try the current trunk.