https://gcc.gnu.org/g:a4a23171994a253cfb9eeafda7a7b710a62317b4
commit a4a23171994a253cfb9eeafda7a7b710a62317b4
Author: Michael Meissner <meiss...@linux.ibm.com>
Date: Wed Jul 9 01:49:05 2025 -0400
PR target/117251: Improve vector eqv to vector xor 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 #28 of 45 to generate the 'XXEVAL' instruction on power10
and power11 instead of using the Altivec 'VEQV' instruction feeding
into 'VXOR'. 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:
veqv t,c,d
vxor 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,150
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 eqv => xor 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 e5ea37c567d6..bb62ae26445a 100644
--- a/gcc/config/rs6000/fusion.md
+++ b/gcc/config/rs6000/fusion.md
@@ -2987,20 +2987,23 @@
;; logical-logical fusion pattern generated by gen_logical_addsubf
;; vector veqv -> vxor
(define_insn "*fuse_veqv_vxor"
- [(set (match_operand:VM 3 "altivec_register_operand" "=&0,&1,&v,v")
- (xor:VM (not:VM (xor:VM (match_operand:VM 0 "altivec_register_operand"
"v,v,v,v")
- (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")
+ (xor:VM (not:VM (xor:VM (match_operand:VM 0 "vector_fusion_operand"
"v,v,v,wa,v")
+ (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)"
"@
veqv %3,%1,%0\;vxor %3,%3,%2
veqv %3,%1,%0\;vxor %3,%3,%2
veqv %3,%1,%0\;vxor %3,%3,%2
+ xxeval %x3,%x2,%x1,%x0,150
veqv %4,%1,%0\;vxor %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 vnand -> vxor
diff --git a/gcc/config/rs6000/genfusion.pl b/gcc/config/rs6000/genfusion.pl
index d713d10a1dbc..726e29c798bc 100755
--- a/gcc/config/rs6000/genfusion.pl
+++ b/gcc/config/rs6000/genfusion.pl
@@ -242,6 +242,7 @@ sub gen_logical_addsubf
"vnor_vxor" => 135,
"vnor_vor" => 143,
"vxor_vnor" => 144,
+ "veqv_vxor" => 150,
);
KIND: foreach $kind ('scalar','vector') {
