https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120925
Bug ID: 120925 Summary: partial kortest pattern not recognized Product: gcc Version: 16.0 Status: UNCONFIRMED Keywords: missed-optimization Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: mkretz at gcc dot gnu.org Target Milestone: --- Target: x86_64-* i?86-*-* Test case (https://compiler-explorer.com/z/ebTT6W664): static constexpr unsigned char im = 0x3f; inline bool all_of1(unsigned char k) { return (k & im) == im; } inline bool all_of2(unsigned char k) { return __builtin_ia32_kortestcqi(k, ~im); } using V [[gnu::vector_size(8 * 8)]] = double; inline unsigned char eq(V a, V b) { return __builtin_ia32_cmppd512_mask(a, b, 0x00, -1, 0x04); } V f1(V a, V b) { if (all_of1(eq(a, b))) return a; else return V(); } V f2(V a, V b) { if (all_of2(eq(a, b))) return a; else return V(); } f1 and f2 are equivalent functions. The all_of1 & branch in f1 should be recognized and transformed into a kortest instruction. I can think of two patterns: 1. if((__mmaskN & k1) == k1) 2. if((__mmaskN | __mmaskN(~k1)) == ~__mmaskN)