[gcc(refs/users/meissner/heads/work235-sha)] PR target/117251: Improve vector nand to vector and fusion

[Michael Meissner]

https://gcc.gnu.org/g:ae2a7802aeaa619363b7482024018037e3e83213

commit ae2a7802aeaa619363b7482024018037e3e83213
Author: Michael Meissner <meissner@linux.ibm.com>
Date:   Fri Jan 30 16:46:16 2026 -0500

    PR target/117251: Improve vector nand to vector and 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 #9 of 45 to generate the 'XXEVAL' instruction on power10
    and power11 instead of using the Altivec 'VNAND' instruction feeding
    into 'VAND'.  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
            vand   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,14
    
    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  <meissner@linux.ibm.com>
    
    gcc/
    
            PR target/117251
            * config/rs6000/fusion.md: Regenerate.
            * config/rs6000/genfusion.pl (gen_logical_addsubf): Add support
            to generate vector/vector nand/and 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 6b283c2f29e1..6b4610d2188b 100644
--- a/gcc/config/rs6000/fusion.md
+++ b/gcc/config/rs6000/fusion.md
@@ -1934,20 +1934,23 @@
 ;; logical-logical fusion pattern generated by gen_logical_addsubf
 ;; vector vnand -> vand
 (define_insn "*fuse_vnand_vand"
-  [(set (match_operand:VM 3 "altivec_register_operand" "=&0,&1,&v,v")
-        (and: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")
+        (and: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\;vand %3,%3,%2
    vnand %3,%1,%0\;vand %3,%3,%2
    vnand %3,%1,%0\;vand %3,%3,%2
+   xxeval %x3,%x2,%x1,%x0,14
    vnand %4,%1,%0\;vand %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 -> vand
diff --git a/gcc/config/rs6000/genfusion.pl b/gcc/config/rs6000/genfusion.pl
index 53021a8005b7..3257f80580e1 100755
--- a/gcc/config/rs6000/genfusion.pl
+++ b/gcc/config/rs6000/genfusion.pl
@@ -223,6 +223,7 @@ sub gen_logical_addsubf
       "veqv_vand"   =>   9,
       "vorc_vand"   =>  11,
       "vandc_vandc" =>  13,
+      "vnand_vand"  =>  14,
     );
 
     KIND: foreach $kind ('scalar','vector') {