Hi Richard,
On Mon, 3 Dec 2018 at 14:37, Richard Biener <[email protected]> wrote:
>
>
> This fixes a missed optimization in EVRP by teaching the code
> figuring out conditional asserts about conversions that preserve
> the converted value.
>
> Bootstrapped and tested on x86_64-unknown-linux-gnu, applied to trunk
> sofar.
>
> Richard.
>
> 2018-12-03 Richard Biener <[email protected]>
>
> PR tree-optimization/88301
> * tree-vrp.c (register_edge_assert_for_2): Handle conversions
> that do not change the value by registering the same assert
> for the operand.
>
> * gcc.dg/tree-ssa/evrp13.c: New testcase.
>
I noticed a regression in g++ on aarch64, and git bisect indicates
this commits is the culprit.
g++.dg/warn/Wstringop-overflow-1.C -std=c++14 (test for warnings, line 14)
g++.dg/warn/Wstringop-overflow-1.C -std=c++14 (test for excess errors)
g++.dg/warn/Wstringop-overflow-1.C -std=c++17 (test for warnings, line 14)
g++.dg/warn/Wstringop-overflow-1.C -std=c++17 (test for excess errors)
g++.dg/warn/Wstringop-overflow-1.C -std=c++98 (test for warnings, line 14)
g++.dg/warn/Wstringop-overflow-1.C -std=c++98 (test for excess errors)
g++.log says:
Excess errors:
/gcc/testsuite/g++.dg/warn/Wstringop-overflow-1.C:14:21: warning:
'char* __builtin_strncpy(char*, const char*, long unsigned int)'
writing between 6 and 2147483647 bytes into a region of size 5
overflows the destination [-Wstringop-overflow=]
Christophe
> Index: gcc/tree-vrp.c
> ===================================================================
> --- gcc/tree-vrp.c (revision 266733)
> +++ gcc/tree-vrp.c (working copy)
> @@ -2966,6 +2966,23 @@ register_edge_assert_for_2 (tree name, e
> add_assert_info (asserts, name2, tmp, new_comp_code, new_val);
> }
>
> + /* If we have a conversion that doesn't change the value of the source
> + simply register the same assert for it. */
> + if (CONVERT_EXPR_CODE_P (rhs_code))
> + {
> + wide_int rmin, rmax;
> + tree rhs1 = gimple_assign_rhs1 (def_stmt);
> + if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
> + && int_fits_type_p (val, TREE_TYPE (rhs1))
> + && ((TYPE_PRECISION (TREE_TYPE (name))
> + > TYPE_PRECISION (TREE_TYPE (rhs1)))
> + || (get_range_info (rhs1, &rmin, &rmax) == VR_RANGE
> + && wi::fits_to_tree_p (rmin, TREE_TYPE (name))
> + && wi::fits_to_tree_p (rmax, TREE_TYPE (name)))))
> + add_assert_info (asserts, rhs1, rhs1,
> + comp_code, fold_convert (TREE_TYPE (rhs1), val));
> + }
> +
> /* Add asserts for NAME cmp CST and NAME being defined as
> NAME = NAME2 & CST2.
>
> Index: gcc/testsuite/gcc.dg/tree-ssa/evrp13.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/tree-ssa/evrp13.c (revision 0)
> +++ gcc/testsuite/gcc.dg/tree-ssa/evrp13.c (working copy)
> @@ -0,0 +1,7 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fdump-tree-evrp" } */
> +
> +#define ADD_NW(A,B) (__extension__({ __typeof(A+B) R;
> if(__builtin_add_overflow(A,B,&R)) __builtin_unreachable(); R ;}))
> +_Bool a_b2(unsigned A, unsigned B) { return ADD_NW(A,B) >= B; }
> +
> +/* { dg-final { scan-tree-dump "return 1;" "evrp" } } */
