https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116024
--- Comment #9 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <l...@gcc.gnu.org>: https://gcc.gnu.org/g:0883c88664d48463dfc79335dccaf15a69230952 commit r15-4186-g0883c88664d48463dfc79335dccaf15a69230952 Author: Artemiy Volkov <artemiy.vol...@synopsys.com> Date: Tue Oct 8 17:51:08 2024 -0600 tree-optimization/116024 - simplify C1-X cmp C2 for UB-on-overflow types Implement a match.pd pattern for C1 - X cmp C2, where C1 and C2 are integer constants and X is of a UB-on-overflow type. The pattern is simplified to X rcmp C1 - C2 by moving X and C2 to the other side of the comparison (with opposite signs). If C1 - C2 happens to overflow, replace the whole expression with either a constant 0 or a constant 1 node, depending on the comparison operator and the sign of the overflow. This transformation allows to occasionally save load-immediate / subtraction instructions, e.g. the following statement: 10 - (int) x <= 9; now compiles to sgt a0,a0,zero instead of li a5,10 sub a0,a5,a0 slti a0,a0,10 on 32-bit RISC-V. Additional examples can be found in the newly added test file. This patch has been bootstrapped and regtested on aarch64, x86_64, and i386, and additionally regtested on riscv32. Existing tests were adjusted where necessary. gcc/ChangeLog: PR tree-optimization/116024 * match.pd: New transformation around integer comparison. gcc/testsuite/ChangeLog: * gcc.dg/tree-ssa/pr116024.c: New test. * gcc.dg/pr67089-6.c: Adjust.
