On 11/21/18 2:33 PM, Uros Bizjak wrote:
Hello!
Before the recent patch to post-reload mode switching, vzeroupper
insertion depended on the existence of the return copy instructions
pair in functions that return a value. The first instruction in the
pair represents a move to a function return hard register, and the
second was a USE of the function return hard register. Sometimes a nop
move was generated (e.g. %eax->%eax) for the first instruction of the
return copy instructions pair and the patch [1] teached LRA to remove
these useless instructions on the fly.
The removal caused optimize mode switching to trigger the assert,
since the first instruction of a return pair was not found. The
relevant part of the patch was later reverted. With the recent
optimize mode switching patch, this is no longer necessary for
vzeroupper insertion pass, so attached patch reverts the revert.
2018-11-21 Uros Bizjak <ubiz...@gmail.com>
Revert the revert:
2013-10-26 Vladimir Makarov <vmaka...@redhat.com>
Revert:
2013-10-25 Vladimir Makarov <vmaka...@redhat.com>
* lra-spills.c (lra_final_code_change): Remove useless move insns.
Patch was bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
OK for mainline?
Sure, Uros. I support the patch. But I think it would be wise to
postpone its committing after releasing GCC-9. Simply it is hard to
predict the patch effect to other targets and I would avoid any risk at
this stage.
[1] https://gcc.gnu.org/ml/gcc-patches/2013-10/msg02208.html
Uros.
