[Bug target/95078] Missing fwprop for SIB address
rguenth at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Tue May 12 11:34:33 GMT 2020
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95078
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
TER should go away, not be extended. So you are suggesting that we replace
leaq 44(%rdi,%rdx,4), %rdx --- redundant could be fwprop
movl (%rdx), %eax
movl $3, (%rsi)
addl (%rdx), %eax
with
movl 44(%rdi,%rdx,4), %eax
movl $3, (%rsi)
addl 44(%rdi,%rdx,4), %eax
? The variant that looks bigger is actually one byte smaller. Note as
soon as there are three uses it will be larger again...
So this is really something for RTL and yeah, fwprop only makes "local"
decisions. Note that I think that your proposed variant will consume
more resources since the complex addressing modes are likely split into
a separate uop. Yes, overall I'd expect less latency for your sequence.
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