mirror of
https://github.com/crosstool-ng/crosstool-ng.git
synced 2024-12-22 22:22:23 +00:00
380ac20c2d
[This]patch is a bit more involved. The patch addresses a gcc regression in the 4.3 series (specifically this patch is against 4.3.2 which does *not* have a lot of other issues which affect kernel building) GCC bug tracker has this issue as #38453 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38453 #32044 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=32044 comment 65 of #32044 has the fix being applied to gcc trunk as revision #142719 The attached patch is a backport to gcc 4.3.2 which allows this version to be used to generate correct output for various ARM kernel build (and indeed is teh correct answer in general). /trunk/patches/gcc/4.3.2/360-fix-expensive-optimize.patch | 207 207 0 0 +++++++++++++++++++++ 1 file changed, 207 insertions(+)
208 lines
6.4 KiB
Diff
208 lines
6.4 KiB
Diff
PR tree-optimization/32044
|
|
|
|
From: rakdver
|
|
Date: 2008-12-12 21:32:47 +0100
|
|
|
|
* tree-scalar-evolution.h (expression_expensive_p): Declare.
|
|
* tree-scalar-evolution.c (expression_expensive_p): New function.
|
|
(scev_const_prop): Avoid introducing expensive expressions.
|
|
* tree-ssa-loop-ivopts.c (may_eliminate_iv): Ditto.
|
|
|
|
* gcc.dg/pr34027-1.c: Change outcome.
|
|
* gcc.dg/tree-ssa/pr32044.c: New test.
|
|
|
|
cherry picked from svn://gcc.gnu.org/svn/gcc/trunk, rev 142719 and adapted to
|
|
apply on gcc 4.3.2
|
|
|
|
------------------------------------------------------------------------
|
|
Index: gcc-4.3.2/gcc/tree-scalar-evolution.c
|
|
===================================================================
|
|
--- gcc-4.3.2.orig/gcc/tree-scalar-evolution.c 2009-01-28 10:14:37.000000000 +0100
|
|
+++ gcc-4.3.2/gcc/tree-scalar-evolution.c 2009-01-28 10:17:50.000000000 +0100
|
|
@@ -2716,6 +2716,50 @@
|
|
scalar_evolution_info = NULL;
|
|
}
|
|
|
|
+/* Returns true if the expression EXPR is considered to be too expensive
|
|
+ for scev_const_prop. */
|
|
+
|
|
+bool
|
|
+expression_expensive_p (tree expr)
|
|
+{
|
|
+ enum tree_code code;
|
|
+
|
|
+ if (is_gimple_val (expr))
|
|
+ return false;
|
|
+
|
|
+ code = TREE_CODE (expr);
|
|
+ if (code == TRUNC_DIV_EXPR
|
|
+ || code == CEIL_DIV_EXPR
|
|
+ || code == FLOOR_DIV_EXPR
|
|
+ || code == ROUND_DIV_EXPR
|
|
+ || code == TRUNC_MOD_EXPR
|
|
+ || code == CEIL_MOD_EXPR
|
|
+ || code == FLOOR_MOD_EXPR
|
|
+ || code == ROUND_MOD_EXPR
|
|
+ || code == EXACT_DIV_EXPR)
|
|
+ {
|
|
+ /* Division by power of two is usually cheap, so we allow it.
|
|
+ Forbid anything else. */
|
|
+ if (!integer_pow2p (TREE_OPERAND (expr, 1)))
|
|
+ return true;
|
|
+ }
|
|
+
|
|
+ switch (TREE_CODE_CLASS (code))
|
|
+ {
|
|
+ case tcc_binary:
|
|
+ case tcc_comparison:
|
|
+ if (expression_expensive_p (TREE_OPERAND (expr, 1)))
|
|
+ return true;
|
|
+
|
|
+ /* Fallthru. */
|
|
+ case tcc_unary:
|
|
+ return expression_expensive_p (TREE_OPERAND (expr, 0));
|
|
+
|
|
+ default:
|
|
+ return true;
|
|
+ }
|
|
+}
|
|
+
|
|
/* Replace ssa names for that scev can prove they are constant by the
|
|
appropriate constants. Also perform final value replacement in loops,
|
|
in case the replacement expressions are cheap.
|
|
@@ -2802,12 +2846,6 @@
|
|
continue;
|
|
|
|
niter = number_of_latch_executions (loop);
|
|
- /* We used to check here whether the computation of NITER is expensive,
|
|
- and avoided final value elimination if that is the case. The problem
|
|
- is that it is hard to evaluate whether the expression is too
|
|
- expensive, as we do not know what optimization opportunities the
|
|
- the elimination of the final value may reveal. Therefore, we now
|
|
- eliminate the final values of induction variables unconditionally. */
|
|
if (niter == chrec_dont_know)
|
|
continue;
|
|
|
|
@@ -2838,7 +2876,15 @@
|
|
/* Moving the computation from the loop may prolong life range
|
|
of some ssa names, which may cause problems if they appear
|
|
on abnormal edges. */
|
|
- || contains_abnormal_ssa_name_p (def))
|
|
+ || contains_abnormal_ssa_name_p (def)
|
|
+ /* Do not emit expensive expressions. The rationale is that
|
|
+ when someone writes a code like
|
|
+
|
|
+ while (n > 45) n -= 45;
|
|
+
|
|
+ he probably knows that n is not large, and does not want it
|
|
+ to be turned into n %= 45. */
|
|
+ || expression_expensive_p (def))
|
|
continue;
|
|
|
|
/* Eliminate the PHI node and replace it by a computation outside
|
|
Index: gcc-4.3.2/gcc/tree-scalar-evolution.h
|
|
===================================================================
|
|
--- gcc-4.3.2.orig/gcc/tree-scalar-evolution.h 2009-01-28 10:22:47.000000000 +0100
|
|
+++ gcc-4.3.2/gcc/tree-scalar-evolution.h 2009-01-28 10:23:10.000000000 +0100
|
|
@@ -35,6 +35,7 @@
|
|
extern void scev_analysis (void);
|
|
unsigned int scev_const_prop (void);
|
|
|
|
+bool expression_expensive_p (tree);
|
|
extern bool simple_iv (struct loop *, tree, tree, affine_iv *, bool);
|
|
|
|
/* Returns the loop of the polynomial chrec CHREC. */
|
|
Index: gcc-4.3.2/gcc/testsuite/gcc.dg/pr34027-1.c
|
|
===================================================================
|
|
--- gcc-4.3.2.orig/gcc/testsuite/gcc.dg/pr34027-1.c 2009-01-28 10:24:09.000000000 +0100
|
|
+++ gcc-4.3.2/gcc/testsuite/gcc.dg/pr34027-1.c 2009-01-28 10:24:43.000000000 +0100
|
|
@@ -8,5 +8,9 @@
|
|
return ns;
|
|
}
|
|
|
|
-/* { dg-final { scan-tree-dump "ns % 10000" "optimized" } } */
|
|
+/* This test was originally introduced to test that we transform
|
|
+ to ns % 10000. See the discussion of PR 32044 why we do not do
|
|
+ that anymore. */
|
|
+/* { dg-final { scan-tree-dump-times "%" 0 "optimized" } } */
|
|
+/* { dg-final { scan-tree-dump-times "/" 0 "optimized" } } */
|
|
/* { dg-final { cleanup-tree-dump "optimized" } } */
|
|
Index: gcc-4.3.2/gcc/testsuite/gcc.dg/tree-ssa/pr32044.c
|
|
===================================================================
|
|
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
|
|
+++ gcc-4.3.2/gcc/testsuite/gcc.dg/tree-ssa/pr32044.c 2009-01-28 10:25:50.000000000 +0100
|
|
@@ -0,0 +1,55 @@
|
|
+/* { dg-do compile } */
|
|
+/* { dg-options "-O2 -fdump-tree-empty -fdump-tree-final_cleanup" } */
|
|
+
|
|
+int foo (int n)
|
|
+{
|
|
+ while (n >= 45)
|
|
+ n -= 45;
|
|
+
|
|
+ return n;
|
|
+}
|
|
+
|
|
+int bar (int n)
|
|
+{
|
|
+ while (n >= 64)
|
|
+ n -= 64;
|
|
+
|
|
+ return n;
|
|
+}
|
|
+
|
|
+int bla (int n)
|
|
+{
|
|
+ int i = 0;
|
|
+
|
|
+ while (n >= 45)
|
|
+ {
|
|
+ i++;
|
|
+ n -= 45;
|
|
+ }
|
|
+
|
|
+ return i;
|
|
+}
|
|
+
|
|
+int baz (int n)
|
|
+{
|
|
+ int i = 0;
|
|
+
|
|
+ while (n >= 64)
|
|
+ {
|
|
+ i++;
|
|
+ n -= 64;
|
|
+ }
|
|
+
|
|
+ return i;
|
|
+}
|
|
+
|
|
+/* The loops computing division/modulo by 64 should be eliminated. */
|
|
+/* { dg-final { scan-tree-dump-times "Removing empty loop" 2 "empty" } } */
|
|
+
|
|
+/* There should be no division/modulo in the final dump (division and modulo
|
|
+ by 64 are done using bit operations). */
|
|
+/* { dg-final { scan-tree-dump-times "/" 0 "final_cleanup" } } */
|
|
+/* { dg-final { scan-tree-dump-times "%" 0 "final_cleanup" } } */
|
|
+
|
|
+/* { dg-final { cleanup-tree-dump "empty" } } */
|
|
+/* { dg-final { cleanup-tree-dump "final_cleanup" } } */
|
|
Index: gcc-4.3.2/gcc/tree-ssa-loop-ivopts.c
|
|
===================================================================
|
|
--- gcc-4.3.2.orig/gcc/tree-ssa-loop-ivopts.c 2009-01-28 10:26:04.000000000 +0100
|
|
+++ gcc-4.3.2/gcc/tree-ssa-loop-ivopts.c 2009-01-28 10:27:09.000000000 +0100
|
|
@@ -3778,7 +3778,12 @@
|
|
return false;
|
|
|
|
cand_value_at (loop, cand, use->stmt, nit, &bnd);
|
|
+
|
|
*bound = aff_combination_to_tree (&bnd);
|
|
+ /* It is unlikely that computing the number of iterations using division
|
|
+ would be more profitable than keeping the original induction variable. */
|
|
+ if (expression_expensive_p (*bound))
|
|
+ return false;
|
|
return true;
|
|
}
|
|
|
|
|