https://gcc.gnu.org/g:3928830b0fa97afc8f2ca54b7a9b203c8502dc3a
commit 3928830b0fa97afc8f2ca54b7a9b203c8502dc3a
Author: Michael Meissner <meiss...@linux.ibm.com>
Date: Wed Jul 9 01:55:11 2025 -0400
PR target/117251: Improve vector xor to vector nand 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 #42 of 45 to generate the 'XXEVAL' instruction on power10
and power11 instead of using the Altivec 'VXOR' instruction feeding
into 'VNAND'. 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:
vxor t,c,d
vnand 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,249
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 xor => nand 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 39b586918c17..e0f9ac17659a 100644
--- a/gcc/config/rs6000/fusion.md
+++ b/gcc/config/rs6000/fusion.md
@@ -2477,20 +2477,23 @@
;; logical-logical fusion pattern generated by gen_logical_addsubf
;; vector vxor -> vnand
(define_insn "*fuse_vxor_vnand"
- [(set (match_operand:VM 3 "altivec_register_operand" "=&0,&1,&v,v")
- (ior: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")))
- (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")
+ (ior: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")))
+ (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)"
"@
vxor %3,%1,%0\;vnand %3,%3,%2
vxor %3,%1,%0\;vnand %3,%3,%2
vxor %3,%1,%0\;vnand %3,%3,%2
+ xxeval %x3,%x2,%x1,%x0,249
vxor %4,%1,%0\;vnand %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 vand -> vnor
diff --git a/gcc/config/rs6000/genfusion.pl b/gcc/config/rs6000/genfusion.pl
index 86bca81286ca..5d22a0732df6 100755
--- a/gcc/config/rs6000/genfusion.pl
+++ b/gcc/config/rs6000/genfusion.pl
@@ -256,6 +256,7 @@ sub gen_logical_addsubf
"veqv_vnand" => 246,
"vnor_vnand" => 247,
"vor_vnand" => 248,
+ "vxor_vnand" => 249,
);
KIND: foreach $kind ('scalar','vector') {
