https://gcc.gnu.org/g:6474b6dbad0c66976adf904bfa942e9d76764947
commit 6474b6dbad0c66976adf904bfa942e9d76764947
Author: Michael Meissner <meiss...@linux.ibm.com>
Date: Wed Jul 9 01:40:03 2025 -0400
PR target/117251: Improve vector nand to vector nor 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 #10 of 45 to generate the 'XXEVAL' instruction on power10
and power11 instead of using the Altivec 'VNAND' instruction feeding
into 'VNOR'. 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
vnor 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,16
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?
2025-07-09 Michael Meissner <meiss...@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/nor 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 f70422616ffd..c8a27a9e5471 100644
--- a/gcc/config/rs6000/fusion.md
+++ b/gcc/config/rs6000/fusion.md
@@ -2528,20 +2528,23 @@
;; logical-logical fusion pattern generated by gen_logical_addsubf
;; vector vnand -> vnor
(define_insn "*fuse_vnand_vnor"
- [(set (match_operand:VM 3 "altivec_register_operand" "=&0,&1,&v,v")
- (and:VM (not: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"))))
- (not:VM (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 (not: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"))))
+ (not:VM (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\;vnor %3,%3,%2
vnand %3,%1,%0\;vnor %3,%3,%2
vnand %3,%1,%0\;vnor %3,%3,%2
+ xxeval %x3,%x2,%x1,%x0,16
vnand %4,%1,%0\;vnor %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 -> vnor
diff --git a/gcc/config/rs6000/genfusion.pl b/gcc/config/rs6000/genfusion.pl
index 5beabe530a67..078bc6ca0dab 100755
--- a/gcc/config/rs6000/genfusion.pl
+++ b/gcc/config/rs6000/genfusion.pl
@@ -224,6 +224,7 @@ sub gen_logical_addsubf
"vorc_vand" => 11,
"vandc_vandc" => 13,
"vnand_vand" => 14,
+ "vnand_vnor" => 16,
);
KIND: foreach $kind ('scalar','vector') {
