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This is my proposed minimal fix for PR target/109973 (hopefully suitable for backporting) that follows Jakub Jelinek's suggestion that we introduce CCZmode and CCCmode variants of ptest and vptest, so that the i386 backend treats [v]ptest instructions similarly to testl instructions; using different CCmodes to indicate which condition flags are desired, and then relying on the RTL cmpelim pass to eliminate redundant tests. This conveniently matches Intel's intrinsics, that provide different functions for retrieving different flags, _mm_testz_si128 tests the Z flag, _mm_testc_si128 tests the carry flag. Currently we use the same instruction (pattern) for both, and unfortunately the *ptest<mode>_and optimization is only valid when the ptest/vptest instruction is used to set/test the Z flag. The downside, as predicted by Jakub, is that GCC's cmpelim pass is currently COMPARE-centric and not able to merge the ptests from expressions such as _mm256_testc_si256 (a, b) + _mm256_testz_si256 (a, b), which is a known issue, PR target/80040. 2023-06-01 Roger Sayle <roger@nextmovesoftware.com> Uros Bizjak <ubizjak@gmail.com> gcc/ChangeLog PR target/109973 * config/i386/i386-builtin.def (__builtin_ia32_ptestz128): Use new CODE_for_sse4_1_ptestzv2di. (__builtin_ia32_ptestc128): Use new CODE_for_sse4_1_ptestcv2di. (__builtin_ia32_ptestz256): Use new CODE_for_avx_ptestzv4di. (__builtin_ia32_ptestc256): Use new CODE_for_avx_ptestcv4di. * config/i386/i386-expand.cc (ix86_expand_branch): Use CCZmode when expanding UNSPEC_PTEST to compare against zero. * config/i386/i386-features.cc (scalar_chain::convert_compare): Likewise generate CCZmode UNSPEC_PTESTs when converting comparisons. (general_scalar_chain::convert_insn): Use CCZmode for COMPARE result. (timode_scalar_chain::convert_insn): Use CCZmode for COMPARE result. * config/i386/i386-protos.h (ix86_match_ptest_ccmode): Prototype. * config/i386/i386.cc (ix86_match_ptest_ccmode): New predicate to check for suitable matching modes for the UNSPEC_PTEST pattern. * config/i386/sse.md (define_split): When splitting UNSPEC_MOVMSK to UNSPEC_PTEST, preserve the FLAG_REG mode as CCZ. (*<sse4_1>_ptest<mode>): Add asterisk to hide define_insn. Remove ":CC" mode of FLAGS_REG, instead use ix86_match_ptest_ccmode. (<sse4_1>_ptestz<mode>): New define_expand to specify CCZ. (<sse4_1>_ptestc<mode>): New define_expand to specify CCC. (<sse4_1>_ptest<mode>): A define_expand using CC to preserve the current behavior. (*ptest<mode>_and): Specify CCZ to only perform this optimization when only the Z flag is required. gcc/testsuite/ChangeLog PR target/109973 * gcc.target/i386/pr109973-1.c: New test case. * gcc.target/i386/pr109973-2.c: Likewise. |
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