https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118089
--- Comment #6 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Earnshaw <rearn...@gcc.gnu.org>: https://gcc.gnu.org/g:0b6453d5575d4aa773a1fe25060123bc6f539891 commit r15-7430-g0b6453d5575d4aa773a1fe25060123bc6f539891 Author: Richard Earnshaw <rearn...@arm.com> Date: Fri Feb 7 13:55:58 2025 +0000 arm: Prefer POP {lo-reg} over LDR lo-reg, ... for thumb2 [PR118089] For thumb2, popping a single low register off the stack should prefer POP over LDR to mirror the behaviour of the PUSH on entry. This saves a couple of bytes in the resulting image. This is a relatively niche case as it's rare to push a single low register onto the stack, but still worth getting right. Whilst fixing this I've also restructured the code here somewhat to fix a bug I observed by inspection and to improve the code slightly. Firstly, the single register case is hoisted above the main loop. This not only avoids creating some RTL that immediately becomes garbage but also avoids us needing to check for this case in every iteration of the main loop body. Secondly, we iterate over just the non-zero bits in the reg mask rather than every bit and then checking if there's work to do for that bit. Finally, when emitting a pop that also pops SP off the stack we shouldn't be emitting a stack-adjust CFA note. The new SP value comes from the popped value, not from an adjustment of the previous SP value. gcc: PR target/118089 * config/arm/arm.cc (arm_emit_multi_reg_pop): Restructure. Don't emit LDR on thumb2 when POP can be used for smaller code. Don't add a CFA adjust note when SP is popped off the stack. gcc/testsuite: PR target/118089 * gcc.target/arm/thumb2-pop-loreg.c: New test.
