[PATCH][i386] Fix PR 6585 redundant movl instructions

Paolo Bonzini bonzini@gnu.org
Thu Dec 20 00:03:00 GMT 2007

>    It records a conflict between register 61 and 66 and ends up allocating
> register 61 to (%esi:%ebx) where we would prefer (%edx:%eax). This patch
> fixes it by splitting the DImode destination into two SImode parts before
> register allocation, which allows the second subreg lowering pass to replace
> the subregs with plain SImode regs which the register allocator can handle.


A few hours ago I've attached to PR17236 a patch which obtains the same 
result in a target-independent way.  I'm currently bootstrapping and 
SPEC-testing the patch; I'll let target and middle-end maintainers judge 
which approach to prefer.  Yours has the obvious advantage of being 
localized to the i386 backend (mine touches three passes, local-alloc, 
regclass and combine...).


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