On Tue, Aug 11, 2026 at 5:00 PM Andrea Pinski <[email protected]> wrote: > > This adds some extra checks to see if we can remove the casts > for signed integer overflow reasons while doing a negative. > This is needed more due to the recent patch which adds them > in some cases.
Can't you use expr_not_equal_to (..., INT_MIN)? > Bootstrapped and tested on x86_64-linux-gnu. > > PR tree-optimization/107765 > > gcc/ChangeLog: > > * match.pd (`(cast)-(cast)a`): Expand to use ranger > to see if we can remove the casts. > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/neg-cast-1.c: New test. > * gcc.dg/tree-ssa/neg-cast-4.c: New test. > > Signed-off-by: Andrea Pinski <[email protected]> > --- > gcc/match.pd | 37 ++++++++++++++++++---- > gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c | 23 ++++++++++++++ > gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c | 16 ++++++++++ > 3 files changed, 69 insertions(+), 7 deletions(-) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index 751f5571183..8de356b102c 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -1233,15 +1233,38 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > show up. Else it is safe if the negation is done in an unsigned type. > Note the outer cast cannot be a boolean type as the only valid values > are 0,-1/1 (depending on the signedness of the boolean) and the negative > - is there to get the correct value. */ > + is there to get the correct value. > + Also handle the case where we */ > (simplify > - (convert (negate:s@1 (convert:s @0))) > + (convert (negate:s@1 (convert:s@ic @0))) > (if (INTEGRAL_TYPE_P (type) > - && tree_nop_conversion_p (type, TREE_TYPE (@1)) > - && (TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0)) > - || TYPE_UNSIGNED (type)) > - && TREE_CODE (type) != BOOLEAN_TYPE) > - (negate (convert @0)))) > + && tree_nop_conversion_p (type, TREE_TYPE (@1))) > + (with { > + bool can_handle = false; > +#if GIMPLE > + int_range_max vr; > +#endif > + if ((TYPE_PRECISION (type) > TYPE_PRECISION (TREE_TYPE (@0)) > + || TYPE_UNSIGNED (type)) > + && TREE_CODE (type) != BOOLEAN_TYPE) > + can_handle = true; > + else if (wi::ges_p (tree_nonzero_bits (@ic), 0)) > + can_handle = true; > +#if GIMPLE > + /* If we know that @0 does not contain signed max, then the > + conversion can be removed. */ > + else if (TREE_CODE (@0) == SSA_NAME > + && types_match (type, TREE_TYPE (@0)) > + && get_range_query (cfun)->range_of_expr (vr, @0) > + && !vr.undefined_p ()) > + { > + tree stype = signed_type_for (type); > + can_handle = !vr.contains_p (wi::min_value (stype)); > + } > +#endif > + } > + (if (can_handle) > + (negate (convert @0)))))) > > (for op (negate abs) > /* Simplify cos(-x) and cos(|x|) -> cos(x). Similarly for cosh. */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c > b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c > new file mode 100644 > index 00000000000..ec5d0e15251 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-1.c > @@ -0,0 +1,23 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized -fdump-tree-cddce1" } */ > +/* PR tree-optimization/107765 */ > + > +int a(int input) > +{ > + if (input == -__INT_MAX__-1) return 1; > + unsigned t = input; > + int tt = -t; > + return tt == -input; > +} > + > +int b(int input) > +{ > + if (input == -__INT_MAX__-1) __builtin_trap(); > + unsigned t = input; > + int tt = -t; > + return tt; > +} > + > +/* { dg-final { scan-tree-dump "return 1" "optimized" } } */ > +/* { dg-final { scan-tree-dump-not "\\(unsigned int\\)" "cddce1" } } */ > +/* { dg-final { scan-tree-dump-not "\\(int\\)" "cddce1" } } */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c > b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c > new file mode 100644 > index 00000000000..fe3fe6a2ecc > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/neg-cast-4.c > @@ -0,0 +1,16 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-phiopt2-details -fdump-tree-optimized" } */ > +/* PR tree-optimization/107765 */ > + > +int b(int input) > +{ > + if (input == -__INT_MAX__-1) return input; > + unsigned t = input; > + int tt = -t; > + return tt; > +} > + > +/* { dg-final { scan-tree-dump-not "if " "optimized" } } */ > +/* { dg-final { scan-tree-dump-times "\\(unsigned int\\)" 1 "optimized" } } > */ > +/* { dg-final { scan-tree-dump-times "\\(int\\)" 1 "optimized" } } */ > +/* { dg-final { scan-tree-dump-times "converted to straightline code" 1 > "phiopt2" } } */ > -- > 2.43.0 >
