https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120811
--- Comment #11 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <[email protected]>: https://gcc.gnu.org/g:304d7359a67b8f7b979bf5941c7a5cbabf1aebcf commit r16-4402-g304d7359a67b8f7b979bf5941c7a5cbabf1aebcf Author: Shreya Munnangi <[email protected]> Date: Mon Oct 13 16:13:44 2025 -0600 [RISC-V][PR target/120811] Improving address reloads in LRA In pr120811, we have cases where GCC is emitting an extra addi instruction instead of using the 12-bit signed-immediate of ld. addi t1, t1, 1 ld t1, 0(t1) This problem occurs when fp -> sp+offset elimination results in an out-of-range constant and we generate an address reload in LRA using addsi/adddi expanders. We've already adjusted the expanders to widen the set of valid operands to allow more constants for the 2nd input operand. These expanders, rather than constructing the constant into a register and using an add instruction, will generate two addi instructions (or shNadd) during initial RTL generation. We define a new pattern for cases where we need to access the current frame and the offsets are too large. This gets reasonable code out of LRA in a form fold-mem-offsets can handle, rather than having to wait for sched2 to do the height reduction transformation and leaving in the unnecessary add instruction in the RTL stream. To avoid the two addi instructions being squashed back together in the post-reload combine, we remove the adddi3_const_sum_of_two_s12 pattern. We are seeing about 100 billion dynamic instructions saved which is about 5% on cactuBSSN and a 2% improvement in performance on the BPI. PR target/120811 gcc/ * config/riscv/riscv.cc (synthesize_add): Exchange constant terms when generating addi pairs. (synthesize_addsi): Similarly. * config/riscv/riscv.md (addptr<mode>3): New define_expand. (*add<mode>3_const_sum_of_two_s12): Remove pattern. gcc/testsuite/ * gcc.target/riscv/add-synthesis-1.c: Adjust const to fit in range. * gcc.target/riscv/pr120811.c: Add new test case. * gcc.target/riscv/sum-of-two-s12-const-1.c: Adjust const to fit in range.
