https://gcc.gnu.org/g:795a37a5b3009dbbf1ca0a478d5d7a5776dac978
commit 795a37a5b3009dbbf1ca0a478d5d7a5776dac978 Author: Michael Meissner <[email protected]> Date: Fri Jan 30 17:04:47 2026 -0500 PR target/117251: Improve vector nand to vector or fusion See the following post for a complete explanation of what the patches for PR target/117251: * https://gcc.gnu.org/pipermail/gcc-patches/2025-June/686474.html This is patch #36 of 45 to generate the 'XXEVAL' instruction on power10 and power11 instead of using the Altivec 'VNAND' instruction feeding into 'VOR'. The 'XXEVAL' instruction can use all 64 vector registers, instead of the 32 registers that traditional Altivec vector instructions use. By allowing all of the vector registers to be used, it reduces the amount of spilling that a large benchmark generated. Currently the following code: vector int a, b, c, d; a = (~ (c & d)) | b; Generates: vnand t,c,d vor a,t,b Now in addition with this patch, if the arguments or result is allocated to a traditional FPR register, the GCC compiler will now generate the following code instead of adding vector move instructions: xxeval a,b,c,239 Since fusion using 2 Altivec instructions is slightly faster than using the 'XXEVAL' instruction we prefer to generate the Altivec instructions if we can. In addition, because 'XXEVAL' is a prefixed instruction, it possibly might generate an extra NOP instruction to align the 'XXEVAL' instruction. I have tested these patches on both big endian and little endian PowerPC servers, with no regressions. Can I check these patchs into the trunk? 2026-01-30 Michael Meissner <[email protected]> gcc/ PR target/117251 * config/rs6000/fusion.md: Regenerate. * config/rs6000/genfusion.pl (gen_logical_addsubf): Add support to generate vector nand => or fusion if XXEVAL is supported. Diff: --- gcc/config/rs6000/fusion.md | 15 +++++++++------ gcc/config/rs6000/genfusion.pl | 1 + 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/gcc/config/rs6000/fusion.md b/gcc/config/rs6000/fusion.md index 3f8e8f174109..3e2ca9c2a587 100644 --- a/gcc/config/rs6000/fusion.md +++ b/gcc/config/rs6000/fusion.md @@ -2711,20 +2711,23 @@ ;; logical-logical fusion pattern generated by gen_logical_addsubf ;; vector vnand -> vor (define_insn "*fuse_vnand_vor" - [(set (match_operand:VM 3 "altivec_register_operand" "=&0,&1,&v,v") - (ior:VM (ior:VM (not:VM (match_operand:VM 0 "altivec_register_operand" "v,v,v,v")) - (not:VM (match_operand:VM 1 "altivec_register_operand" "v,v,v,v"))) - (match_operand:VM 2 "altivec_register_operand" "v,v,v,v"))) - (clobber (match_scratch:VM 4 "=X,X,X,&v"))] + [(set (match_operand:VM 3 "vector_fusion_operand" "=&0,&1,&v,wa,v") + (ior:VM (ior:VM (not:VM (match_operand:VM 0 "vector_fusion_operand" "v,v,v,wa,v")) + (not:VM (match_operand:VM 1 "vector_fusion_operand" "v,v,v,wa,v"))) + (match_operand:VM 2 "vector_fusion_operand" "v,v,v,wa,v"))) + (clobber (match_scratch:VM 4 "=X,X,X,X,&v"))] "(TARGET_P10_FUSION)" "@ vnand %3,%1,%0\;vor %3,%3,%2 vnand %3,%1,%0\;vor %3,%3,%2 vnand %3,%1,%0\;vor %3,%3,%2 + xxeval %x3,%x2,%x1,%x0,239 vnand %4,%1,%0\;vor %3,%4,%2" [(set_attr "type" "fused_vector") (set_attr "cost" "6") - (set_attr "length" "8")]) + (set_attr "length" "8") + (set_attr "prefixed" "*,*,*,yes,*") + (set_attr "isa" "*,*,*,xxeval,*")]) ;; logical-logical fusion pattern generated by gen_logical_addsubf ;; vector vnor -> vor diff --git a/gcc/config/rs6000/genfusion.pl b/gcc/config/rs6000/genfusion.pl index 33b083f9d6f2..8c742a9e6673 100755 --- a/gcc/config/rs6000/genfusion.pl +++ b/gcc/config/rs6000/genfusion.pl @@ -250,6 +250,7 @@ sub gen_logical_addsubf "vandc_veqv" => 210, "vand_vnor" => 224, "vnand_vxor" => 225, + "vnand_vor" => 239, ); KIND: foreach $kind ('scalar','vector') {
