Hi,
I think 20 insns to copy for loop header is way too much. The constant came
from jump.c that was operating with quite different IL and compiler.
This patch adds --param for it so we can fine tune it for new millenia.
Bootstrapped/regtested x86_64-linux, OK?
Honza
* invoke.texi (max-loop-headers-insns): Document.
* params.def (PARAM_MAX_LOOP_HEADER_INSNS): New.
* tree-ssa-loop-ch.c (should_duplicate_loop_header_p): Update comment.
(ch_base::copy_headers): Use PARAM_MAX_LOOP_HEADER_INSNS.
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 237184)
+++ doc/invoke.texi (working copy)
@@ -9066,6 +9066,9 @@ The maximum number of insns of an unswit
@item max-unswitch-level
The maximum number of branches unswitched in a single loop.
+@item max-loop-headers-insns
+The maximum number of insns in loop header duplicated by copy loop headers
pass.
+
@item lim-expensive
The minimum cost of an expensive expression in the loop invariant motion.
Index: params.def
===================================================================
--- params.def (revision 237184)
+++ params.def (working copy)
@@ -344,6 +344,13 @@ DEFPARAM(PARAM_MAX_UNSWITCH_LEVEL,
"The maximum number of unswitchings in a single loop.",
3, 0, 0)
+/* The maximum number of insns in loop header duplicated by copy loop headers
+ pass. */
+DEFPARAM(PARAM_MAX_LOOP_HEADER_INSNS,
+ "max-loop-header-insns",
+ "The maximum number of insns in loop header duplicated by copy loop
headers pass.",
+ 20, 0, 0)
+
/* The maximum number of iterations of a loop the brute force algorithm
for analysis of # of iterations of the loop tries to evaluate. */
DEFPARAM(PARAM_MAX_ITERATIONS_TO_TRACK,
Index: tree-ssa-loop-ch.c
===================================================================
--- tree-ssa-loop-ch.c (revision 237184)
+++ tree-ssa-loop-ch.c (working copy)
@@ -33,6 +33,7 @@ along with GCC; see the file COPYING3.
#include "tree-inline.h"
#include "tree-ssa-scopedtables.h"
#include "tree-ssa-threadedge.h"
+#include "params.h"
/* Duplicates headers of loops if they are small enough, so that the statements
in the loop body are always executed when the loop is entered. This
@@ -106,8 +107,7 @@ should_duplicate_loop_header_p (basic_bl
return false;
}
- /* Approximately copy the conditions that used to be used in jump.c --
- at most 20 insns and no calls. */
+ /* Count number of instructions and punt on calls. */
for (bsi = gsi_start_bb (header); !gsi_end_p (bsi); gsi_next (&bsi))
{
last = gsi_stmt (bsi);
@@ -290,8 +290,8 @@ ch_base::copy_headers (function *fun)
FOR_EACH_LOOP (loop, 0)
{
- /* Copy at most 20 insns. */
- int limit = 20;
+ int ninsns = PARAM_VALUE (PARAM_MAX_LOOP_HEADER_INSNS);
+ int limit = ninsns;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file,
"Analyzing loop %i\n", loop->num);
@@ -333,7 +333,8 @@ ch_base::copy_headers (function *fun)
fprintf (dump_file,
"Duplicating header of the loop %d up to edge %d->%d,"
" %i insns.\n",
- loop->num, exit->src->index, exit->dest->index, 20 - limit);
+ loop->num, exit->src->index, exit->dest->index,
+ ninsns - limit);
/* Ensure that the header will have just the latch as a predecessor
inside the loop. */
