OpenE2K
/
gcc
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

re PR tree-optimization/79721 (Scalar evolution introduces signed overflow) 

2017-03-01  Richard Biener  <rguenther@suse.de>

	PR middle-end/79721
	* tree-chrec.c (chrec_evaluate): Perform computation of Newtons
	interpolating formula in wrapping arithmetic.
	(chrec_apply): Convert chrec_evaluate return value to wanted type.

	* gcc.dg/torture/pr79721.c: New testcase.

From-SVN: r245803
This commit is contained in:
Richard Biener 2017-03-01 08:54:29 +00:00 committed by Richard Biener
parent e3e9e8ca83
commit 0100ae4302
4 changed files with 50 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
gcc/ChangeLog
View File

@ -1,3 +1,10 @@
2017-03-01 Richard Biener <rguenther@suse.de>
PR middle-end/79721
* tree-chrec.c (chrec_evaluate): Perform computation of Newtons
interpolating formula in wrapping arithmetic.
(chrec_apply): Convert chrec_evaluate return value to wanted type.
2017-03-01 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/79734

5
gcc/testsuite/ChangeLog
View File

@ -1,3 +1,8 @@
2017-03-01 Richard Biener <rguenther@suse.de>
PR middle-end/79721
* gcc.dg/torture/pr79721.c: New testcase.
2017-03-01 Jakub Jelinek <jakub@redhat.com>
PR c++/79746

21
gcc/testsuite/gcc.dg/torture/pr79721.c Normal file
View File

@ -0,0 +1,21 @@
/* { dg-do run } */
/* { dg-require-effective-target int32plus } */
/* We use -ftrapv so that when SCEV final value replacement introduces
undefined overflow we trap. UBSAN inhibits final value replacement. */
/* { dg-additional-options "-ftrapv" } */
int __attribute__((noclone,noinline))
foo(int a, int b)
{
int sum = 0;
for (int i = 0; i < 60000; i++)
sum += a + i * b;
return sum;
}
int main(int argc, char **argv)
{
if (foo (-30000, 2) != 1799940000)
__builtin_abort ();
return 0;
}

25
gcc/tree-chrec.c
View File

@ -536,7 +536,8 @@ tree_fold_binomial (tree type, tree n, unsigned int k)
}
/* Helper function. Use the Newton's interpolating formula for
evaluating the value of the evolution function. */
evaluating the value of the evolution function.
The result may be in an unsigned type of CHREC. */
static tree
chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
@ -549,25 +550,33 @@ chrec_evaluate (unsigned var, tree chrec, tree n, unsigned int k)
&& flow_loop_nested_p (var_loop, get_chrec_loop (chrec)))
chrec = CHREC_LEFT (chrec);
/* The formula associates the expression and thus we have to make
sure to not introduce undefined overflow. */
tree ctype = type;
if (INTEGRAL_TYPE_P (type)
&& ! TYPE_OVERFLOW_WRAPS (type))
ctype = unsigned_type_for (type);
if (TREE_CODE (chrec) == POLYNOMIAL_CHREC
&& CHREC_VARIABLE (chrec) == var)
{
arg1 = chrec_evaluate (var, CHREC_RIGHT (chrec), n, k + 1);
if (arg1 == chrec_dont_know)
return chrec_dont_know;
binomial_n_k = tree_fold_binomial (type, n, k);
binomial_n_k = tree_fold_binomial (ctype, n, k);
if (!binomial_n_k)
return chrec_dont_know;
arg0 = fold_build2 (MULT_EXPR, type,
CHREC_LEFT (chrec), binomial_n_k);
return chrec_fold_plus (type, arg0, arg1);
tree l = chrec_convert (ctype, CHREC_LEFT (chrec), NULL);
arg0 = fold_build2 (MULT_EXPR, ctype, l, binomial_n_k);
return chrec_fold_plus (ctype, arg0, arg1);
}
binomial_n_k = tree_fold_binomial (type, n, k);
binomial_n_k = tree_fold_binomial (ctype, n, k);
if (!binomial_n_k)
return chrec_dont_know;
return fold_build2 (MULT_EXPR, type, chrec, binomial_n_k);
return fold_build2 (MULT_EXPR, ctype,
chrec_convert (ctype, chrec, NULL), binomial_n_k);
}
/* Evaluates "CHREC (X)" when the varying variable is VAR.
@ -623,7 +632,7 @@ chrec_apply (unsigned var,
else if (TREE_CODE (x) == INTEGER_CST
&& tree_int_cst_sgn (x) == 1)
/* testsuite/.../ssa-chrec-38.c. */
res = chrec_evaluate (var, chrec, x, 0);
res = chrec_convert (type, chrec_evaluate (var, chrec, x, 0), NULL);
else
res = chrec_dont_know;
break;