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re PR middle-end/53676 (empty loop is not always removed now) 

2012-06-27  Richard Guenther  <rguenther@suse.de>

	PR middle-end/53676
	* tree-chrec.c (chrec_convert_1): Represent truncation to
	a type with undefined overflow as truncation to an unsigned
	type converted to the type with undefined overflow.
	* tree-scalar-evolution.c (interpret_rhs_expr): For computing
	the scalar evolution of a truncated widened operation avoid
	looking at the non-existing evolution of the widened operation
	result.

	* gcc.dg/tree-ssa/scev-6.c: New testcase.

From-SVN: r189013
This commit is contained in:
Richard Guenther 2012-06-27 11:32:30 +00:00 committed by Richard Biener
parent be7493cabb
commit 195b4c507f
5 changed files with 80 additions and 1 deletions
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11
gcc/ChangeLog
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@ -1,3 +1,14 @@
2012-06-27 Richard Guenther <rguenther@suse.de>
PR middle-end/53676
* tree-chrec.c (chrec_convert_1): Represent truncation to
a type with undefined overflow as truncation to an unsigned
type converted to the type with undefined overflow.
* tree-scalar-evolution.c (interpret_rhs_expr): For computing
the scalar evolution of a truncated widened operation avoid
looking at the non-existing evolution of the widened operation
result.
2012-06-27 Richard Guenther <rguenther@suse.de>
PR tree-optimization/53774

5
gcc/testsuite/ChangeLog
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@ -1,3 +1,8 @@
2012-06-27 Richard Guenther <rguenther@suse.de>
PR middle-end/53676
* gcc.dg/tree-ssa/scev-6.c: New testcase.
2012-06-26 Janis Johnson <janisjo@codesourcery.com>
* lib/scandump.exp (scan-dump, scan-dump-not, scan-dump-dem,

23
gcc/testsuite/gcc.dg/tree-ssa/scev-6.c Normal file
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@ -0,0 +1,23 @@
/* { dg-do run } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
int main()
{
int i;
signed char result = 0;
for (i = 0; i != 8000; ++i)
{
int tem = result;
tem = tem + 2;
result = tem;
}
if (__builtin_abs ((int)(signed char)((unsigned char ) result + 128)) != 0)
__builtin_abort ();
return 0;
}
/* SCEV constant propagation should be able to compute the overall effect
of the loop. */
/* { dg-final { scan-tree-dump-not "abort" "optimized" } } */
/* { dg-final { cleanup-tree-dump "optimized" } } */

17
gcc/tree-chrec.c
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@ -1365,6 +1365,23 @@ keep_cast:
res = fold_build2 (TREE_CODE (chrec), type,
fold_convert (type, TREE_OPERAND (chrec, 0)),
fold_convert (type, TREE_OPERAND (chrec, 1)));
/* Similar perform the trick that (signed char)((int)x + 2) can be
narrowed to (signed char)((unsigned char)x + 2). */
else if (use_overflow_semantics
&& TREE_CODE (chrec) == POLYNOMIAL_CHREC
&& TREE_CODE (ct) == INTEGER_TYPE
&& TREE_CODE (type) == INTEGER_TYPE
&& TYPE_OVERFLOW_UNDEFINED (type)
&& TYPE_PRECISION (type) < TYPE_PRECISION (ct))
{
tree utype = unsigned_type_for (type);
res = build_polynomial_chrec (CHREC_VARIABLE (chrec),
fold_convert (utype,
CHREC_LEFT (chrec)),
fold_convert (utype,
CHREC_RIGHT (chrec)));
res = chrec_convert_1 (type, res, at_stmt, use_overflow_semantics);
}
else
res = fold_convert (type, chrec);

25
gcc/tree-scalar-evolution.c
View File

@ -1634,6 +1634,7 @@ interpret_rhs_expr (struct loop *loop, gimple at_stmt,
tree type, tree rhs1, enum tree_code code, tree rhs2)
{
tree res, chrec1, chrec2;
gimple def;
if (get_gimple_rhs_class (code) == GIMPLE_SINGLE_RHS)
{
@ -1759,7 +1760,29 @@ interpret_rhs_expr (struct loop *loop, gimple at_stmt,
break;
CASE_CONVERT:
chrec1 = analyze_scalar_evolution (loop, rhs1);
/* In case we have a truncation of a widened operation that in
the truncated type has undefined overflow behavior analyze
the operation done in an unsigned type of the same precision
as the final truncation. We cannot derive a scalar evolution
for the widened operation but for the truncated result. */
if (TREE_CODE (type) == INTEGER_TYPE
&& TREE_CODE (TREE_TYPE (rhs1)) == INTEGER_TYPE
&& TYPE_PRECISION (type) < TYPE_PRECISION (TREE_TYPE (rhs1))
&& TYPE_OVERFLOW_UNDEFINED (type)
&& TREE_CODE (rhs1) == SSA_NAME
&& (def = SSA_NAME_DEF_STMT (rhs1))
&& is_gimple_assign (def)
&& TREE_CODE_CLASS (gimple_assign_rhs_code (def)) == tcc_binary
&& TREE_CODE (gimple_assign_rhs2 (def)) == INTEGER_CST)
{
tree utype = unsigned_type_for (type);
chrec1 = interpret_rhs_expr (loop, at_stmt, utype,
gimple_assign_rhs1 (def),
gimple_assign_rhs_code (def),
gimple_assign_rhs2 (def));
}
else
chrec1 = analyze_scalar_evolution (loop, rhs1);
res = chrec_convert (type, chrec1, at_stmt);
break;