re PR tree-optimization/81303 (410.bwaves regression caused by r249919)

	PR tree-optimization/81303
	* Makefile.in (gimple-loop-interchange.o): New object file.
	* common.opt (floop-interchange): Reuse the option from graphite.
	* doc/invoke.texi (-floop-interchange): Ditto.  New document for
	-floop-interchange and mention it for -O3.
	* opts.c (default_options_table): Enable -floop-interchange at -O3.
	* gimple-loop-interchange.cc: New file.
	* params.def (PARAM_LOOP_INTERCHANGE_MAX_NUM_STMTS): New parameter.
	(PARAM_LOOP_INTERCHANGE_STRIDE_RATIO): New parameter.
	* passes.def (pass_linterchange): New pass.
	* timevar.def (TV_LINTERCHANGE): New time var.
	* tree-pass.h (make_pass_linterchange): New declaration.
	* tree-ssa-loop-ivcanon.c (create_canonical_iv): Change to external
	interchange.  Record IV before/after increment in new parameters.
	* tree-ssa-loop-ivopts.h (create_canonical_iv): New declaration.
	* tree-vect-loop.c (vect_is_simple_reduction): Factor out reduction
	path check into...
	(check_reduction_path): ...New function here.
	* tree-vectorizer.h (check_reduction_path): New declaration.

	gcc/testsuite
	* gcc.dg/tree-ssa/loop-interchange-1.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-1b.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-2.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-3.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-4.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-5.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-6.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-7.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-8.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-9.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-10.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-11.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-12.c: New test.
	* gcc.dg/tree-ssa/loop-interchange-13.c: New test.

Co-Authored-By: Richard Biener <rguenther@suse.de>

From-SVN: r255472

1 files changed, 26 insertions, 2 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 447b66a..50740c5 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -7409,6 +7409,7 @@ by @option{-O2} and also turns on the following optimization flags:
 -ftree-loop-vectorize @gol
 -ftree-loop-distribution @gol
 -ftree-loop-distribute-patterns @gol
+-floop-interchange @gol
 -fsplit-paths @gol
 -ftree-slp-vectorize @gol
 -fvect-cost-model @gol
@@ -8508,12 +8509,10 @@ Perform loop optimizations on trees.  This flag is enabled by default
 at @option{-O} and higher.
 
 @item -ftree-loop-linear
-@itemx -floop-interchange
 @itemx -floop-strip-mine
 @itemx -floop-block
 @itemx -floop-unroll-and-jam
 @opindex ftree-loop-linear
-@opindex floop-interchange
 @opindex floop-strip-mine
 @opindex floop-block
 @opindex floop-unroll-and-jam
@@ -8608,6 +8607,25 @@ ENDDO
 @end smallexample
 and the initialization loop is transformed into a call to memset zero.
 
+@item -floop-interchange
+@opindex floop-interchange
+Perform loop interchange outside of graphite.  This flag can improve cache
+performance on loop nest and allow further loop optimizations, like
+vectorization, to take place.  For example, the loop
+@smallexample
+for (int i = 0; i < N; i++)
+  for (int j = 0; j < N; j++)
+    for (int k = 0; k < N; k++)
+      c[i][j] = c[i][j] + a[i][k]*b[k][j];
+@end smallexample
+is transformed to
+@smallexample
+for (int i = 0; i < N; i++)
+  for (int k = 0; k < N; k++)
+    for (int j = 0; j < N; j++)
+      c[i][j] = c[i][j] + a[i][k]*b[k][j];
+@end smallexample
+
 @item -ftree-loop-im
 @opindex ftree-loop-im
 Perform loop invariant motion on trees.  This pass moves only invariants that
@@ -10479,6 +10497,12 @@ The size of L1 cache, in kilobytes.
 @item l2-cache-size
 The size of L2 cache, in kilobytes.
 
+@item loop-interchange-max-num-stmts
+The maximum number of stmts in a loop to be interchanged.
+
+@item loop-interchange-stride-ratio
+The minimum ratio between stride of two loops for interchange to be profitable.
+
 @item min-insn-to-prefetch-ratio
 The minimum ratio between the number of instructions and the
 number of prefetches to enable prefetching in a loop.