https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88873
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:12b78b0b42d53019eb2c500d386094194e90ad16 commit r14-2406-g12b78b0b42d53019eb2c500d386094194e90ad16 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Mon Jul 10 09:06:52 2023 +0100 i386: Add new insvti_lowpart_1 and insvdi_lowpart_1 patterns. This patch implements another of Uros' suggestions, to investigate a insvti_lowpart_1 pattern to improve TImode parameter passing on x86_64. In PR 88873, the RTL the middle-end expands for passing V2DF in TImode is subtly different from what it does for V2DI in TImode, sufficiently so that my explanations for why insvti_lowpart_1 isn't required don't apply in this case. This patch adds an insvti_lowpart_1 pattern, complementing the existing insvti_highpart_1 pattern, and also a 32-bit variant, insvdi_lowpart_1. Because the middle-end represents 128-bit constants using CONST_WIDE_INT and 64-bit constants using CONST_INT, it's easiest to treat these as different patterns, rather than attempt <dwi> parameterization. This patch also includes a peephole2 (actually a pair) to transform xchg instructions into mov instructions, when one of the destinations is unused. This optimization is required to produce the optimal code sequences below. For the 64-bit case: __int128 foo(__int128 x, unsigned long long y) { __int128 m = ~((__int128)~0ull); __int128 t = x & m; __int128 r = t | y; return r; } Before: xchgq %rdi, %rsi movq %rdx, %rax xorl %esi, %esi xorl %edx, %edx orq %rsi, %rax orq %rdi, %rdx ret After: movq %rdx, %rax movq %rsi, %rdx ret For the 32-bit case: long long bar(long long x, int y) { long long mask = ~0ull << 32; long long t = x & mask; long long r = t | (unsigned int)y; return r; } Before: pushl %ebx movl 12(%esp), %edx xorl %ebx, %ebx xorl %eax, %eax movl 16(%esp), %ecx orl %ebx, %edx popl %ebx orl %ecx, %eax ret After: movl 12(%esp), %eax movl 8(%esp), %edx ret 2023-07-10 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog * config/i386/i386.md (peephole2): Transform xchg insn with a REG_UNUSED note to a (simple) move. (*insvti_lowpart_1): New define_insn_and_split. (*insvdi_lowpart_1): Likewise. gcc/testsuite/ChangeLog * gcc.target/i386/insvdi_lowpart-1.c: New test case. * gcc.target/i386/insvti_lowpart-1.c: Likewise.
