Hi,
since this caused a critical performance regression in the OpenJ9 byte code
interpreter after
migrating from GCC 4.8 to GCC 7 I would like to backport this patch also to GCC
8 and 9 branch.
Ok - after bootstrap and regression test went fine?
Andreas
commit d3dc20418aad41af83fe45ccba527deb0b334983
Author: krebbel <krebbel@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Thu Jun 6 11:35:04 2019 +0000
Fix PR88751
This patch implements a small improvement for the heuristic in lra
which decides when it has to activate the simpler register allocation
algorithm.
gcc/ChangeLog:
2019-06-06 Andreas Krebbel <kreb...@linux.ibm.com>
PR rtl-optimization/88751
* ira.c (ira): Use the number of the actually referenced registers
when calculating the threshold.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@271996
138bc75d-0d04-0410-961f-82ee72b054a4
diff --git a/gcc/ira.c b/gcc/ira.c
index 4a14fb31583..725636d8dc5 100644
--- a/gcc/ira.c
+++ b/gcc/ira.c
@@ -5198,6 +5198,8 @@ ira (FILE *f)
int ira_max_point_before_emit;
bool saved_flag_caller_saves = flag_caller_saves;
enum ira_region saved_flag_ira_region = flag_ira_region;
+ unsigned int i;
+ int num_used_regs = 0;
clear_bb_flags ();
@@ -5213,12 +5215,17 @@ ira (FILE *f)
ira_conflicts_p = optimize > 0;
+ /* Determine the number of pseudos actually requiring coloring. */
+ for (i = FIRST_PSEUDO_REGISTER; i < DF_REG_SIZE (df); i++)
+ num_used_regs += !!(DF_REG_USE_COUNT (i) + DF_REG_DEF_COUNT (i));
+
/* If there are too many pseudos and/or basic blocks (e.g. 10K
pseudos and 10K blocks or 100K pseudos and 1K blocks), we will
use simplified and faster algorithms in LRA. */
lra_simple_p
= (ira_use_lra_p
- && max_reg_num () >= (1 << 26) / last_basic_block_for_fn (cfun));
+ && num_used_regs >= (1 << 26) / last_basic_block_for_fn (cfun));
+
if (lra_simple_p)
{
/* It permits to skip live range splitting in LRA. */
