| Message ID | alpine.DEB.2.02.1303191659110.4515@stedding.saclay.inria.fr |
|---|---|
| State | New |
| Headers | show |
On 03/19/2013 10:08 AM, Marc Glisse wrote: > Hello, > > this patch extends the property that x*x is non-negative, which was > already known for floats, to integers with undefined overflow. > > 2013-03-19 Marc Glisse <marc.glisse@inria.fr> > > PR tree-optimization/56355 > gcc/ > * fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>: > Also handle integers with undefined overflow. > > gcc/testsuite/ > * gcc.dg/pr56355-1.c: New file. Fine for the trunk. Though I would suggest waiting for http service & web archives to return before committing. BTW, did you check if VRP creates a non-negative range for this case as well? jeff
On Tue, 19 Mar 2013, Jeff Law wrote: > On 03/19/2013 10:08 AM, Marc Glisse wrote: >> Hello, >> >> this patch extends the property that x*x is non-negative, which was >> already known for floats, to integers with undefined overflow. >> >> 2013-03-19 Marc Glisse <marc.glisse@inria.fr> >> >> PR tree-optimization/56355 >> gcc/ >> * fold-const.c (tree_binary_nonnegative_warnv_p) <MULT_EXPR>: >> Also handle integers with undefined overflow. >> >> gcc/testsuite/ >> * gcc.dg/pr56355-1.c: New file. > Fine for the trunk. Though I would suggest waiting for http service & web > archives to return before committing. Yep. > BTW, did you check if VRP creates a non-negative range for this case as well? It doesn't :-( It would probably need to be done in extract_range_from_binary_expr since extract_range_from_binary_expr_1 does not see the expression, maybe after calling extract_range_from_binary_expr_1, and we would remove the negative part of the interval it returned.
Index: gcc/testsuite/gcc.dg/pr56355-1.c =================================================================== --- gcc/testsuite/gcc.dg/pr56355-1.c (revision 0) +++ gcc/testsuite/gcc.dg/pr56355-1.c (revision 0) @@ -0,0 +1,8 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -Wstrict-overflow=4" } */ + +int +f (int i) +{ + return __builtin_abs (i * i); /* { dg-warning "assuming signed overflow" } */ +} Property changes on: gcc/testsuite/gcc.dg/pr56355-1.c ___________________________________________________________________ Added: svn:eol-style + native Added: svn:keywords + Author Date Id Revision URL Index: gcc/fold-const.c =================================================================== --- gcc/fold-const.c (revision 196633) +++ gcc/fold-const.c (working copy) @@ -15286,29 +15286,32 @@ tree_binary_nonnegative_warnv_p (enum tr && TREE_CODE (inner2) == INTEGER_TYPE && TYPE_UNSIGNED (inner2)) { unsigned int prec = MAX (TYPE_PRECISION (inner1), TYPE_PRECISION (inner2)) + 1; return prec < TYPE_PRECISION (type); } } break; case MULT_EXPR: - if (FLOAT_TYPE_P (type)) + if (FLOAT_TYPE_P (type) || TYPE_OVERFLOW_UNDEFINED (type)) { - /* x * x for floating point x is always non-negative. */ - if (operand_equal_p (op0, op1, 0)) - return true; - return (tree_expr_nonnegative_warnv_p (op0, - strict_overflow_p) - && tree_expr_nonnegative_warnv_p (op1, - strict_overflow_p)); + /* x * x is always non-negative for floating point x + or without overflow. */ + if (operand_equal_p (op0, op1, 0) + || (tree_expr_nonnegative_warnv_p (op0, strict_overflow_p) + && tree_expr_nonnegative_warnv_p (op1, strict_overflow_p))) + { + if (TYPE_OVERFLOW_UNDEFINED (type)) + *strict_overflow_p = true; + return true; + } } /* zero_extend(x) * zero_extend(y) is non-negative if x and y are both unsigned and their total bits is shorter than the result. */ if (TREE_CODE (type) == INTEGER_TYPE && (TREE_CODE (op0) == NOP_EXPR || TREE_CODE (op0) == INTEGER_CST) && (TREE_CODE (op1) == NOP_EXPR || TREE_CODE (op1) == INTEGER_CST)) { tree inner0 = (TREE_CODE (op0) == NOP_EXPR) ? TREE_TYPE (TREE_OPERAND (op0, 0))