[Bug tree-optimization/50413] Incorrect instruction is used to shift value of 128 bit xmm0 registrer

aries.nah at gmail dot com gcc-bugzilla@gcc.gnu.org
Thu Sep 15 13:48:00 GMT 2011


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50413

Anatoly <aries.nah at gmail dot com> changed:

           What    |Removed                     |Added
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             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |

--- Comment #4 from Anatoly <aries.nah at gmail dot com> 2011-09-15 13:42:05 UTC ---
It's not serious. 
Yes, I'm not an expert in SSE instructions (and in ASM at all), and it seems
you're right about shifting.
But, the bug is a real. GCC losts lower bit of upper quadword during shifting
by psrlq.
Try to compile my code and check it out.

We have V.bitmap.b63 = V.bitmap.b64; to shift a lower bit of the upper quadword
but GCC has decided not to do this.



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