[gcc r11-9038] rs6000: Disable optimizing multiple xxsetaccz instructions into one xxsetaccz
Peter Bergner
bergner@gcc.gnu.org
Wed Sep 29 19:17:18 GMT 2021
https://gcc.gnu.org/g:1f377a1f51e99bacb8b77b603e69523f79649498
commit r11-9038-g1f377a1f51e99bacb8b77b603e69523f79649498
Author: Peter Bergner <bergner@linux.ibm.com>
Date: Tue Sep 14 10:47:18 2021 -0500
rs6000: Disable optimizing multiple xxsetaccz instructions into one xxsetaccz
Fwprop will happily optimize two xxsetaccz instructions into one xxsetaccz
by propagating the results of the first to the uses of the second.
We really don't want that to happen given the late priming/depriming of
accumulators. I fixed this by making the xxsetaccz source operand an
unspec volatile. I also removed the mma_xxsetaccz define_expand and
define_insn_and_split and replaced it with a simple define_insn.
The expand and splitter patterns were leftovers from the pre opaque mode
code when the xxsetaccz code was part of the movpxi pattern, and we don't
need them now.
Rather than a new test case, I was able to just modify the current test case
to add another __builtin_mma_xxsetaccz call which shows the bad code gen
with unpatched compilers.
2021-09-14 Peter Bergner <bergner@linux.ibm.com>
gcc/
* config/rs6000/mma.md (unspec): Delete UNSPEC_MMA_XXSETACCZ.
(unspecv): Add UNSPECV_MMA_XXSETACCZ.
(*mma_xxsetaccz): Delete.
(mma_xxsetaccz): Change to define_insn. Remove operand 1.
Use UNSPECV_MMA_XXSETACCZ. Update comment.
* config/rs6000/rs6000.c (rs6000_rtx_costs): Use UNSPECV_MMA_XXSETACCZ.
gcc/testsuite/
* gcc.target/powerpc/mma-builtin-6.c: Add second call to xxsetacc
built-in. Update instruction counts.
(cherry picked from commit f80b9be083e0e7d49e7744b7e531b9aa52acd563)
Diff:
---
gcc/config/rs6000/mma.md | 31 ++++++++----------------
gcc/config/rs6000/rs6000.c | 2 +-
gcc/testsuite/gcc.target/powerpc/mma-builtin-6.c | 14 ++++++-----
3 files changed, 19 insertions(+), 28 deletions(-)
diff --git a/gcc/config/rs6000/mma.md b/gcc/config/rs6000/mma.md
index 1f6fc03d2ac..1990a2183f6 100644
--- a/gcc/config/rs6000/mma.md
+++ b/gcc/config/rs6000/mma.md
@@ -91,7 +91,10 @@
UNSPEC_MMA_XVI8GER4SPP
UNSPEC_MMA_XXMFACC
UNSPEC_MMA_XXMTACC
- UNSPEC_MMA_XXSETACCZ
+ ])
+
+(define_c_enum "unspecv"
+ [UNSPECV_MMA_XXSETACCZ
])
;; MMA instructions with 1 accumulator argument
@@ -467,30 +470,16 @@
"<acc> %A0"
[(set_attr "type" "mma")])
-;; We can't have integer constants in XOmode so we wrap this in an UNSPEC.
-
-(define_expand "mma_xxsetaccz"
- [(set (match_operand:XO 0 "fpr_reg_operand")
- (const_int 0))]
- "TARGET_MMA"
-{
- rtx xo0 = gen_rtx_UNSPEC (XOmode, gen_rtvec (1, const0_rtx),
- UNSPEC_MMA_XXSETACCZ);
- emit_insn (gen_rtx_SET (operands[0], xo0));
- DONE;
-})
+;; We can't have integer constants in XOmode so we wrap this in an
+;; UNSPEC_VOLATILE.
-(define_insn_and_split "*mma_xxsetaccz"
+(define_insn "mma_xxsetaccz"
[(set (match_operand:XO 0 "fpr_reg_operand" "=d")
- (unspec:XO [(match_operand 1 "const_0_to_1_operand" "O")]
- UNSPEC_MMA_XXSETACCZ))]
+ (unspec_volatile:XO [(const_int 0)]
+ UNSPECV_MMA_XXSETACCZ))]
"TARGET_MMA"
"xxsetaccz %A0"
- "&& reload_completed"
- [(set (match_dup 0) (unspec:XO [(match_dup 1)] UNSPEC_MMA_XXSETACCZ))]
- ""
- [(set_attr "type" "mma")
- (set_attr "length" "4")])
+ [(set_attr "type" "mma")])
(define_insn "mma_<vv>"
[(set (match_operand:XO 0 "fpr_reg_operand" "=&d")
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 8cdb9369ee0..3bd9643409e 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -21939,7 +21939,7 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int outer_code,
break;
case UNSPEC:
- if (XINT (x, 1) == UNSPEC_MMA_XXSETACCZ)
+ if (XINT (x, 1) == UNSPECV_MMA_XXSETACCZ)
{
*total = 0;
return true;
diff --git a/gcc/testsuite/gcc.target/powerpc/mma-builtin-6.c b/gcc/testsuite/gcc.target/powerpc/mma-builtin-6.c
index 0c6517211e3..715b28138e9 100644
--- a/gcc/testsuite/gcc.target/powerpc/mma-builtin-6.c
+++ b/gcc/testsuite/gcc.target/powerpc/mma-builtin-6.c
@@ -5,14 +5,16 @@
void
foo (__vector_quad *dst)
{
- __vector_quad acc;
- __builtin_mma_xxsetaccz (&acc);
- *dst = acc;
+ __vector_quad acc0, acc1;
+ __builtin_mma_xxsetaccz (&acc0);
+ __builtin_mma_xxsetaccz (&acc1);
+ dst[0] = acc0;
+ dst[1] = acc1;
}
/* { dg-final { scan-assembler-not {\mlxv\M} } } */
/* { dg-final { scan-assembler-not {\mlxvp\M} } } */
/* { dg-final { scan-assembler-not {\mxxmtacc\M} } } */
-/* { dg-final { scan-assembler-times {\mxxsetaccz\M} 1 } } */
-/* { dg-final { scan-assembler-times {\mxxmfacc\M} 1 } } */
-/* { dg-final { scan-assembler-times {\mstxvp\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mxxsetaccz\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mxxmfacc\M} 2 } } */
+/* { dg-final { scan-assembler-times {\mstxvp\M} 4 } } */
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