https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108247
Andrew Waterman <andrew at sifive dot com> changed:
What |Removed |Added
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CC| |andrew at sifive dot com
--- Comment #1 from Andrew Waterman <andrew at sifive dot com> ---
The base-ISA-only code sequence has the same instruction count but smaller code
size:
slli a1, a1, 1
addw a0, a1, a0
ret
I guess this example is a proxy for a broader set of missed optimizations, some
of which are actually improved by Zba, so maybe my comment is moot. But it
would be best not to de-optimize code size in pursuit of opportunities to use
the Zba instructions.
(It also occurs to me that the sh1add + sext.w sequence is easier to fuse
because the instructions have the same destination. But choosing to increase
code size to avail a fusion opportunity is a uarch-specific tuning decision.)
