[Bug target/23302] [4.1 Regression] extra move generated on x86

[hubicka at gcc dot gnu dot org]

------- Additional Comments From hubicka at gcc dot gnu dot org  2005-09-28 16:51 -------
The actual problem here is that from combine's point of view the two
alternatives (lea preceeded by loads, or add with memory operand followed by
shift) looks equivalent and previously the shorter sequence was purely choosed
by luck because combine followed the right edge first. It is not quite possible
to solve this by combine's splitting mechanizm as the number of instruction
don't change before the read-modify instructions are broken up.

While it might be probably possible to design peephole or combiner insn patter
I am tempted to close this and PR 23303 as WONTFIX as it seems to me we was
optimizing this by pure luck and the patch seems to have overall positive effect
on code size...

Honza

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23302