On Tue, Jun 06, 2023 at 11:31:42PM +0100, Roger Sayle wrote: > > This patch resolves PR target/110104, a missed optimization on x86 around > adc with memory operands. In i386.md, there's a peephole2 after the > pattern for *add<mode>3_cc_overflow_1 that converts the sequence > reg = add(reg,mem); mem = reg [where the reg is dead afterwards] into > the equivalent mem = add(mem,reg). The equivalent peephole2 for adc > is missing (after addcarry<mode>), and is added by this patch. > > For the example code provided in the bugzilla PR:
Seems to be pretty much the same as one of the 12 define_peephole2 patterns I've posted in https://gcc.gnu.org/pipermail/gcc-patches/2023-June/620821.html > 2023-06-07 Roger Sayle <ro...@nextmovesoftware.com> > > gcc/ChangeLog > PR target/110104 > * config/i386/i386.md (define_peephole2): Transform reg=adc(reg,mem) > followed by mem=reg into mem=adc(mem,reg) when applicable. > > gcc/testsuite/ChangeLog > PR target/110104 > * gcc.target/i386/pr110104.c: New test case. The testcase will be useful though (but I'd go with including the intrin header and using the intrinsic rather than builtin). Jakub
