On 3/23/23 8:47 AM, Jeff Law wrote: > On 3/23/23 04:38, Ajit Agarwal wrote: >> * ree.cc: Modification for AND opcode support to eliminate >> unnecessary signed extension. >> * testsuite/g++.target/powerpc/sext-elim.C: New tests. > Just a note. I'll look at this once the trunk is open for gcc-14 development. > It's really not appropriate for gcc-13.
Hi Jeff, yes, we agree 100% that this is stage1 material! I'm sorry if this wasn't clear. >> https://gcc.gnu.org/PR41742 > > These are not addressed in the trunk patch, because int c is not initialized > with registers and for this reason we cannot eliminate them. If we initialize > int c then zero extension goes away. I'm sorry that I don't know how REE works. Why can't it optimize this? I see in the REE dump: (insn 20 18 22 3 (set (reg:DI 4 4) (zero_extend:DI (reg:QI 4 4 [orig:120 cD.3556+3 ] [120]))) "pr41742.c":6:41 8 {zero_extendqidi2} (nil)) (call_insn 22 20 41 3 (parallel [ (set (reg:DI 3 3) (call (mem:SI (symbol_ref:DI ("memset") [flags 0x41] <function_decl 0x7fff925f8400 __builtin_memset>) [0 memsetD.1196 S4 A8]) (const_int 64 [0x40]))) (use (const_int 0 [0])) (clobber (reg:DI 96 lr)) ... Is there a reason why REE cannot see that our (reg:QI 4) is a param register and thus due to our ABI, already correctly sign/zero extended? >> https://gcc.gnu.org/PR65010 >> https://gcc.gnu.org/PR82940 >> https://gcc.gnu.org/PR107949 >> > > My patch fixes these PR's which were not fixed in trunk patch. Great! Once this goes is, please include these PR #s in your commit log and mark the PRs as RESOLVED/FIXED. That said, I see we don't enable -free at -O2 and above like other architectures do, so we'll get no benefit without explicitly adding -free: ./gcc/common/config/riscv/riscv-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ./gcc/common/config/aarch64/aarch64-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ./gcc/common/config/h8300/h8300-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ./gcc/common/config/i386/i386-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ./gcc/common/config/sparc/sparc-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ./gcc/common/config/alpha/alpha-common.cc: { OPT_LEVELS_2_PLUS, OPT_free, NULL, 1 }, ...maybe we should enable it too (in a separate patch) once yours goes in now that it will actually do something for us? Thoughts? I'll note the docs/man page only mention x86, Aarch64 and Alpha enabling REE at -O2 and above, but clearly others have been added since, so if we enable REE at -O2 and above, we should fix that too. Peter
