1547 /* If this insn loads a parameter from its stack slot, then it
1548 represents a savings, rather than a cost, if the parameter is
1549 stored in memory. Record this fact.
1550
1551 Similarly if we're loading other constants from memory (constant
1552 pool, TOC references, small data areas, etc) and this is the only
1553 assignment to the destination pseudo.
At that time, preferred regclass is unknown, and GENERAL_REGS is used to
record memory move cost, but it's not accurate especially for large vector
modes, i.e. 512-bit vector in x86 which would most probably allocate with
SSE_REGS instead of GENERAL_REGS. Using GENERAL_REGS here will overestimate
the cost of this load and make RA propagate the memeory operand into many
consume instructions which causes worse performance.
Fortunately, NO_REGS is used to record the best scenario, so the patch uses
NO_REGS instead of GENERAL_REGS here, it could help RA in PR108707.
Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}
and aarch64-linux-gnu.
Ok for trunk?
gcc/ChangeLog:
PR rtl-optimization/108707
* ira-costs.cc (scan_one_insn): Use NO_REGS instead of
GENERAL_REGS when preferred reg_class is not known.
gcc/testsuite/ChangeLog:
* gcc.target/i386/pr108707.c: New test.
---
gcc/ira-costs.cc | 5 ++++-
gcc/testsuite/gcc.target/i386/pr108707.c | 16 ++++++++++++++++
2 files changed, 20 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/i386/pr108707.c
diff --git a/gcc/ira-costs.cc b/gcc/ira-costs.cc
index c0fdef807dd..d2a801ab9b0 100644
--- a/gcc/ira-costs.cc
+++ b/gcc/ira-costs.cc
@@ -1572,7 +1572,10 @@ scan_one_insn (rtx_insn *insn)
&& (! ira_use_lra_p || ! pic_offset_table_rtx
|| ! contains_symbol_ref_p (XEXP (note, 0))))
{
- enum reg_class cl = GENERAL_REGS;
+ /* Costs for NO_REGS are used in cost calculation on the
+ 1st pass when the preferred register classes are not
+ known yet. In this case we take the best scenario. */
+ enum reg_class cl = NO_REGS;
rtx reg = SET_DEST (set);
int num = COST_INDEX (REGNO (reg));
diff --git a/gcc/testsuite/gcc.target/i386/pr108707.c
b/gcc/testsuite/gcc.target/i386/pr108707.c
new file mode 100644
index 00000000000..bc1a476f551
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr108707.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-mavx512f -O2" } */
+/* { dg-final { scan-assembler-not {(?n)vfmadd[1-3]*ps.*\(} } } */
+/* { dg-final { scan-assembler-times {(?n)vfmadd[1-3]*ps[ \t]*} 3 } } */
+
+#include<immintrin.h>
+
+void
+foo (__m512 pv, __m512 a, __m512 b, __m512 c,
+ __m512* pdest, __m512* p1)
+{
+ __m512 t = *p1;
+ pdest[0] = _mm512_fmadd_ps (t, pv, a);
+ pdest[1] = _mm512_fmadd_ps (t, pv, b);
+ pdest[2] = _mm512_fmadd_ps (t, pv, c);
+}
--
2.39.1.388.g2fc9e9ca3c
