https://gcc.gnu.org/bugzilla/show_bug.cgi?id=31985
--- Comment #4 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:95020d33ad6991fe4fbdccf70e7133116cac68f4 commit r14-1892-g95020d33ad6991fe4fbdccf70e7133116cac68f4 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Fri Jun 16 16:18:27 2023 +0100 PR target/31985: Improve memory operand use with doubleword add. This patch addresses the last remaining issue with PR target/31985, that GCC could make better use of memory addressing modes when implementing double word addition. This is achieved by adding a define_insn_and_split that combines an *add<dwi>3_doubleword with a *concat<mode><dwi>3, so that the components of the concat can be used directly, without first being loaded into a double word register. For test_c in the bugzilla PR: Before: pushl %ebx subl $16, %esp movl 28(%esp), %eax movl 36(%esp), %ecx movl 32(%esp), %ebx movl 24(%esp), %edx addl %ecx, %eax adcl %ebx, %edx movl %eax, 8(%esp) movl %edx, 12(%esp) addl $16, %esp popl %ebx ret After: test_c: subl $20, %esp movl 36(%esp), %eax movl 32(%esp), %edx addl 28(%esp), %eax adcl 24(%esp), %edx movl %eax, 8(%esp) movl %edx, 12(%esp) addl $20, %esp ret 2023-06-16 Roger Sayle <ro...@nextmovesoftware.com> Uros Bizjak <ubiz...@gmail.com> gcc/ChangeLog PR target/31985 * config/i386/i386.md (*add<dwi>3_doubleword_concat): New define_insn_and_split combine *add<dwi>3_doubleword with a *concat<mode><dwi>3 for more efficient lowering after reload. gcc/testsuite/ChangeLog PR target/31985 * gcc.target/i386/pr31985.c: New test case.
