Hi All,
The following patch has been bootstrapped and regtested on powerpc64le-linux.
Disable easy_vector_constant_msb and easy_vector_constant_add_self splitters on
POWER10. On POWER9, bypass these splitters when xxspltib can directly generate
8-bit signed constants, for avoiding redundant vaddubm/vslb sequences. For
word constants on POWER9, retain the splitters since xxspltiw is not available.
2025-07-21 Jeevitha Palanisamy <jeevi...@linux.ibm.com>
gcc/
PR target/118480
* config/rs6000/altivec.md (easy_vector_constant_msb splitter): Disable
on POWER10, and on POWER9 when xxspltib can generate the constant.
(easy_vector_constant_add_self splitter): Likewise
gcc/testsuite/
PR target/118480
* gcc.target/powerpc/pr118480-1.c: New
* gcc.target/powerpc/pr118480-2.c: New
* gcc.target/powerpc/vec-splat-constant-v4sf.c: Adjust test to handle
failed case by msb splitter.
diff --git a/gcc/config/rs6000/altivec.md b/gcc/config/rs6000/altivec.md
index 7edc288a656..509681c4e05 100644
--- a/gcc/config/rs6000/altivec.md
+++ b/gcc/config/rs6000/altivec.md
@@ -283,9 +283,14 @@
(define_split
[(set (match_operand:VM 0 "altivec_register_operand")
(match_operand:VM 1 "easy_vector_constant_msb"))]
- "VECTOR_UNIT_ALTIVEC_OR_VSX_P (<MODE>mode) && reload_completed"
+ "VECTOR_UNIT_ALTIVEC_OR_VSX_P (<MODE>mode) && reload_completed
+ && !TARGET_POWER10"
[(const_int 0)]
{
+ int value = 256;
+ int num_insns = -1;
+ if (xxspltib_constant_p (operands[1], <MODE>mode, &num_insns, &value))
+ DONE;
rtx dest = operands[0];
machine_mode mode;
rtvec v;
@@ -321,10 +326,15 @@
(define_split
[(set (match_operand:VM 0 "altivec_register_operand")
(match_operand:VM 1 "easy_vector_constant_add_self"))]
- "VECTOR_UNIT_ALTIVEC_OR_VSX_P (<MODE>mode) && reload_completed"
+ "VECTOR_UNIT_ALTIVEC_OR_VSX_P (<MODE>mode) && reload_completed
+ && !TARGET_POWER10"
[(set (match_dup 0) (match_dup 3))
(set (match_dup 0) (match_dup 4))]
{
+ int value = 256;
+ int num_insns = -1;
+ if (xxspltib_constant_p (operands[1], <MODE>mode, &num_insns, &value))
+ DONE;
rtx dup = gen_easy_altivec_constant (operands[1]);
rtx const_vec;
machine_mode op_mode = <MODE>mode;
diff --git a/gcc/testsuite/gcc.target/powerpc/pr118480-1.c
b/gcc/testsuite/gcc.target/powerpc/pr118480-1.c
new file mode 100644
index 00000000000..6e1d7b45fc1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr118480-1.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mdejagnu-cpu=power9 -mvsx" } */
+
+/* On P9, vec_splats(18) should use xxspltib directly,
+ not the add-self sequence with vaddubm. */
+
+#include <altivec.h>
+
+typedef vector unsigned char vui8_t;
+
+vui8_t test_splat7_char_18(void)
+{
+ return vec_splats((unsigned char)18);
+}
+
+/* { dg-final { scan-assembler "xxspltib" } } */
+/* { dg-final { scan-assembler-not "vaddubm" } } */
+
diff --git a/gcc/testsuite/gcc.target/powerpc/pr118480-2.c
b/gcc/testsuite/gcc.target/powerpc/pr118480-2.c
new file mode 100644
index 00000000000..8c858231848
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr118480-2.c
@@ -0,0 +1,17 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mdejagnu-cpu=power9 -mvsx" } */
+
+/* On P9, vec_splats(-128) should be a single xxspltib,
+ not the msb-splitter sequence with vslb. */
+
+#include <altivec.h>
+
+typedef vector signed char vui8_t;
+
+vui8_t test_msb(void)
+{
+ return vec_splats((signed char)-128);
+}
+
+ /* { dg-final { scan-assembler "xxspltib" } } */
+ /* { dg-final { scan-assembler-not "vslb" } } */
diff --git a/gcc/testsuite/gcc.target/powerpc/vec-splat-constant-v4sf.c
b/gcc/testsuite/gcc.target/powerpc/vec-splat-constant-v4sf.c
index 1f0475cf47a..8f742df2f9f 100644
--- a/gcc/testsuite/gcc.target/powerpc/vec-splat-constant-v4sf.c
+++ b/gcc/testsuite/gcc.target/powerpc/vec-splat-constant-v4sf.c
@@ -33,7 +33,7 @@ v4sf_const_inf (void)
vector float
v4sf_const_m0 (void)
{
- return (vector float) { -0.0f, -0.0f, -0.0f, -0.0f }; /*
XXSPLTIB/VSLW. */
+ return (vector float) { -0.0f, -0.0f, -0.0f, -0.0f }; /* XXSPLTIW */
}
vector float
@@ -57,11 +57,9 @@ v4sf_splats_inf (void)
vector float
v8hi_splats_m0 (void)
{
- return vec_splats (-0.0f); /* XXSPLTIB/VSLW. */
+ return vec_splats (-0.0f); /* XXSPLTIW */
}
-/* { dg-final { scan-assembler-times {\mxxspltiw\M} 6 } } */
-/* { dg-final { scan-assembler-times {\mxxspltib\M} 2 } } */
-/* { dg-final { scan-assembler-times {\mvslw\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mxxspltiw\M} 8 } } */
/* { dg-final { scan-assembler-not {\mlxvx?\M} } } */
/* { dg-final { scan-assembler-not {\mplxv\M} } } */
