https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116826
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jennifer Schmitz <jschm...@gcc.gnu.org>: https://gcc.gnu.org/g:4be7d2d340a013d01a47c43d2feb6826d1b67af0 commit r15-4267-g4be7d2d340a013d01a47c43d2feb6826d1b67af0 Author: Jennifer Schmitz <jschm...@nvidia.com> Date: Wed Sep 25 03:21:22 2024 -0700 match.pd: Fold logarithmic identities. This patch implements 4 rules for logarithmic identities in match.pd under -funsafe-math-optimizations: 1) logN(1.0/a) -> -logN(a). This avoids the division instruction. 2) logN(C/a) -> logN(C) - logN(a), where C is a real constant. Same as 1). 3) logN(a) + logN(b) -> logN(a*b). This reduces the number of calls to log function. 4) logN(a) - logN(b) -> logN(a/b). Same as 4). Tests were added for float, double, and long double. The patch was bootstrapped and regtested on aarch64-linux-gnu and x86_64-linux-gnu, no regression. Additionally, SPEC 2017 fprate was run. While the transform does not seem to be triggered, we also see no non-noise impact on performance. OK for mainline? Signed-off-by: Jennifer Schmitz <jschm...@nvidia.com> gcc/ PR tree-optimization/116826 PR tree-optimization/86710 * match.pd: Fold logN(1.0/a) -> -logN(a), logN(C/a) -> logN(C) - logN(a), logN(a) + logN(b) -> logN(a*b), and logN(a) - logN(b) -> logN(a/b). gcc/testsuite/ PR tree-optimization/116826 PR tree-optimization/86710 * gcc.dg/tree-ssa/log_ident.c: New test.
