On Sat, Sep 12, 2026 at 9:25 AM Andrea Pinski <[email protected]> wrote: > > This adds a pattern to optimize `minmax (a, b) + c` into `minmax (a + c, b + > c)` when > `a + c` and `b + c` are known not to overflow and either `a + c` or `b + c` > simplifies.
Why is this good if either simplifies? Both would be obvious, but either? Also your pattern picks the 2nd operand for simplifies and uses :c to test the other variant. That's of course more expensive than a way to tell genmatch to accept either operand simplifying ... > This shows up in std::vector::push_back : > > ``` > # RANGE [irange] const size_type [0, 2147483647] MASK 0x7fffffff VALUE 0x0 > __room_33 = 2147483647 - _32; > ... > # RANGE [irange] long unsigned int [1, 2147483646] MASK 0x7fffffff VALUE 0x0 > _35 = MIN_EXPR <__room_33, _34>; > # RANGE [irange] long unsigned int [1, 4294967292] > _36 = _32 + _35; > ``` > _32 has a range of `[0, 2147483647]`, _34 has a range of `[1, 2147483646]`. > > This is transformed into: > _t = _32 + _34; > _36 = MIN_EXPR<_t, 2147483647> > > This then allows to remove a condition that was never could be executed too. > > This is currently limited to unsigned types as overflow_free_p does not tell > me if we are going to introduce new undefined overflow; it will return true > for > all TYPE_OVERFLOW_UNDEFINED types. I filed PR 127356 to add a modified > version > of overflow_free_p. But since the types in push_back is unsigned this is > enough > for now. > > Bootstrapped and tested on x86_64-linux-gnu. > > PR tree-optimization/127103 > gcc/ChangeLog: > > * match.pd (`minmax (a, b) + c`): New pattern. > > gcc/testsuite/ChangeLog: > > * gcc.dg/tree-ssa/minmax-plus-1.c: New test. > > Signed-off-by: Andrea Pinski <[email protected]> > --- > gcc/match.pd | 15 +++++++ > gcc/testsuite/gcc.dg/tree-ssa/minmax-plus-1.c | 39 +++++++++++++++++++ > 2 files changed, 54 insertions(+) > create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/minmax-plus-1.c > > diff --git a/gcc/match.pd b/gcc/match.pd > index d6ece84e186..81734b73a7d 100644 > --- a/gcc/match.pd > +++ b/gcc/match.pd > @@ -532,6 +532,21 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) > (if (gimple_match_range_of_expr (vr0, @0, @2) > && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr0)) > (max (plus @0 @0) @1))))) > + > +/* minmax (a, b) + c -> minmax (a + c, b + c) > + if a+c or b+c simplifies and a+c/b+c don't overlfow */ > +(for minmax (min max) > + (simplify > + (plus:c @0 (minmax:cs@3 @1 @2)) > + (with { int_range_max vr0, vr1, vr2; } > + (if (TYPE_UNSIGNED (type) > + && gimple_match_range_of_expr (vr0, @0) > + && gimple_match_range_of_expr (vr1, @1, @3) > + && gimple_match_range_of_expr (vr2, @2, @3) > + && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr1) > + && range_op_handler (PLUS_EXPR).overflow_free_p (vr0, vr2)) > + (minmax (plus @0 @1) (plus! @0 @2)))))) > + > #endif > > /* X * 1, X / 1 -> X. */ > diff --git a/gcc/testsuite/gcc.dg/tree-ssa/minmax-plus-1.c > b/gcc/testsuite/gcc.dg/tree-ssa/minmax-plus-1.c > new file mode 100644 > index 00000000000..75067fdb962 > --- /dev/null > +++ b/gcc/testsuite/gcc.dg/tree-ssa/minmax-plus-1.c > @@ -0,0 +1,39 @@ > +/* { dg-do compile } */ > +/* { dg-options "-O2 -fdump-tree-optimized-raw" } */ > +/* minmax (a, b) + c -> minmax (a + c, b + c) */ > +/* PR tree-optimization/127103 */ > + > +__attribute__((always_inline)) > +static inline unsigned > +min(unsigned a, unsigned b) > +{ > + if (a > b) > + return b; > + return a; > +} > +__attribute__((always_inline)) > +static inline unsigned > +max(unsigned a, unsigned b) > +{ > + if (a < b) > + return b; > + return a; > +} > + > +unsigned f(unsigned a, unsigned t1) > +{ > + if (a > __INT_MAX__) > + return 0; > + unsigned t = __INT_MAX__ - a; > + return a + min(t, a); > +} > + > +unsigned f1(unsigned a, unsigned t1) > +{ > + if (a > __INT_MAX__) > + return 0; > + unsigned t = __INT_MAX__ - a; > + return a + max(t, a); > +} > + > +/* { dg-final { scan-tree-dump-times "gimple_assign <mult_expr, _\[0-9\], > a_\[0-9\].D., 2" 2 "optimized" } } */ > -- > 2.43.0 >
