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* [Bug middle-end/60162] New: [4.9 lra regression] mlra appears to be using the FP registers as a set of spill registers for ARM.
@ 2014-02-12 22:08 ramana at gcc dot gnu.org
  2014-02-12 22:46 ` [Bug rtl-optimization/60162] [4.9 lra regression] mlra appears to be using the FP registers for integer values and then moving on to GPR registers pinskia at gcc dot gnu.org
                   ` (9 more replies)
  0 siblings, 10 replies; 11+ messages in thread
From: ramana at gcc dot gnu.org @ 2014-02-12 22:08 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60162

            Bug ID: 60162
           Summary: [4.9 lra regression] mlra appears to be using the FP
                    registers as a set of spill registers for ARM.
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ramana at gcc dot gnu.org

This is something that I've just noticed with spec2k gzip : longest_match. 

If the function is compiled for a cross arm-none-linux-gnueabihf toolchain with
the following parameters, 

--with-arch=armv7-a --with-fpu=neon --with-float=hard

With a cross toolchain using mlra by default I get code that loads a value into
an FP register and then moves this over to an integer register. While this is
not that big a problem on some of the newer cores, it will be an issue on older
cores where the latency of such transfers can be pretty high.

You can experiment with -mno-lra to see the difference in code generated and
this is essentially something that has shown up rather recently. 

Bisecting and will follow up in the morning with a testcase.


^ permalink raw reply	[flat|nested] 11+ messages in thread
end of thread, other threads:[~2015-01-16 15:46 UTC | newest]

Thread overview: 11+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-02-12 22:08 [Bug middle-end/60162] New: [4.9 lra regression] mlra appears to be using the FP registers as a set of spill registers for ARM ramana at gcc dot gnu.org
2014-02-12 22:46 ` [Bug rtl-optimization/60162] [4.9 lra regression] mlra appears to be using the FP registers for integer values and then moving on to GPR registers pinskia at gcc dot gnu.org
2014-02-13  9:22 ` [Bug rtl-optimization/60162] [4.9 Regression][lra] " rguenth at gcc dot gnu.org
2014-02-13 10:26 ` ramana at gcc dot gnu.org
2014-02-13 12:10 ` ktkachov at gcc dot gnu.org
2014-03-06 21:30 ` vmakarov at gcc dot gnu.org
2014-03-31  9:24 ` rguenth at gcc dot gnu.org
2014-04-22 11:35 ` [Bug rtl-optimization/60162] [4.9/4.10 " jakub at gcc dot gnu.org
2014-07-16 13:27 ` jakub at gcc dot gnu.org
2014-10-30 10:38 ` [Bug rtl-optimization/60162] [4.9/5 " jakub at gcc dot gnu.org
2015-01-16 15:46 ` ramana at gcc dot gnu.org

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