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re PR tree-optimization/17892 (gcc-4.0 should not reassociate floating point add or multiplication)

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PR 17892.
OKed by Roger Sayle.

From-SVN: r88950
This commit is contained in:
Fariborz Jahanian 2004-10-12 20:50:08 +00:00 committed by Fariborz Jahanian
parent 967af719d2
commit 01d8c00bfc
4 changed files with 49 additions and 1 deletions
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8
gcc/ChangeLog
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@ -1,3 +1,11 @@
2004-10-12 Fariborz Jahanian <fjahanian@apple.com>
PR 17892
* tree-ssa-dom.c (unsafe_associative_fp_binop): New function.
(simplify_rhs_and_lookup_avail_expr): Disallow associativity
and constant folding of floating point MULT_EXPR/PLUS_EXPR
expressions.
2004-10-12 Ulrich Weigand <uweigand@de.ibm.com>
* config/s390/s390.c (s390_va_start): Use build_va_arg_indirect_ref.

19
gcc/testsuite/gcc.c-torture/execute/ieee/unsafe-fp-assoc.c Normal file
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@ -0,0 +1,19 @@
#include <float.h>
extern void abort(void);
static const double C = DBL_MAX;
double foo(double x)
{
return ( ( (x * C) * C ) * C);
}
int main ()
{
double d = foo (0.0);
if (d != 0.0)
abort ();
return 0;
}

8
gcc/tree-outof-ssa.c
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@ -1634,12 +1634,20 @@ find_replaceable_in_bb (temp_expr_table_p tab, basic_block bb)
var_map map = tab->map;
value_expr_p p;
ssa_op_iter iter;
bitmap_iterator bi;
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
{
stmt = bsi_stmt (bsi);
ann = stmt_ann (stmt);
if (TREE_CODE (stmt) == ASM_EXPR && ASM_VOLATILE_P (stmt))
{
/* Volatile ASM_EXPRs kill all current expressions. */
EXECUTE_IF_SET_IN_BITMAP ((tab->partition_in_use), 0, partition, bi)
kill_expr (tab, partition, false);
continue;
}
/* Determine if this stmt finishes an existing expression. */
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_USE)
{

15
gcc/tree-ssa-dom.c
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@ -266,6 +266,7 @@ static void restore_currdefs_to_original_value (void);
static void register_definitions_for_stmt (tree);
static edge single_incoming_edge_ignoring_loop_edges (basic_block);
static void restore_nonzero_vars_to_original_value (void);
static inline bool unsafe_associative_fp_binop (tree);
/* Local version of fold that doesn't introduce cruft. */
@ -1549,6 +1550,18 @@ record_equality (tree x, tree y)
record_const_or_copy_1 (x, y, prev_x);
}
/* Return true, if it is ok to do folding of an associative expression.
EXP is the tree for the associative expression. */
static inline bool
unsafe_associative_fp_binop (tree exp)
{
enum tree_code code = TREE_CODE (exp);
return !(!flag_unsafe_math_optimizations
&& (code == MULT_EXPR || code == PLUS_EXPR)
&& FLOAT_TYPE_P (TREE_TYPE (exp)));
}
/* STMT is a MODIFY_EXPR for which we were unable to find RHS in the
hash tables. Try to simplify the RHS using whatever equivalences
we may have recorded.
@ -1608,7 +1621,7 @@ simplify_rhs_and_lookup_avail_expr (struct dom_walk_data *walk_data,
tree rhs_def_rhs = TREE_OPERAND (rhs_def_stmt, 1);
enum tree_code rhs_def_code = TREE_CODE (rhs_def_rhs);
if (rhs_code == rhs_def_code
if ((rhs_code == rhs_def_code && unsafe_associative_fp_binop (rhs))
|| (rhs_code == PLUS_EXPR && rhs_def_code == MINUS_EXPR)
|| (rhs_code == MINUS_EXPR && rhs_def_code == PLUS_EXPR))
{