Re: [PATCH] match.pd: Optimize __builtin_mul_overflow_p (x, cst, (utype)0) to x > ~(utype)0 / cst [PR30314]

[Jakub Jelinek <jakub@redhat.com>]

On Thu, Jun 02, 2022 at 08:36:42AM +0000, Richard Biener wrote:
> > --- gcc/match.pd.jj	2022-06-01 13:54:32.000654151 +0200
> > +++ gcc/match.pd	2022-06-01 15:13:35.473084402 +0200
> > @@ -5969,6 +5969,17 @@ (define_operator_list SYNC_FETCH_AND_AND
> >         && (!TYPE_UNSIGNED (TREE_TYPE (@2)) || TYPE_UNSIGNED (TREE_TYPE (@0))))
> >     (ovf @1 @0))))
> >  
> > +/* Optimize __builtin_mul_overflow_p (x, cst, (utype) 0) if all 3 types
> > +   are unsigned to x > (umax / cst).  */
> > +(simplify
> > + (imagpart (IFN_MUL_OVERFLOW:cs@2 @0 integer_nonzerop@1))
> 
> does :c work here?  I think it is at least ignored, possibly diagnostic
> in genmatch is missing ...

I saw it used in another pattern, so thought it will work fine:
  (cmp:c (realpart (IFN_ADD_OVERFLOW:c@2 @0 @1)) @0)

And looking at the generated source, I think it does work:
              case CFN_MUL_OVERFLOW:
                if (gimple_call_num_args (_c1) == 2)
                  {
                    tree _q20 = gimple_call_arg (_c1, 0);
                    _q20 = do_valueize (valueize, _q20);
                    tree _q21 = gimple_call_arg (_c1, 1);
                    _q21 = do_valueize (valueize, _q21);
                    if (integer_nonzerop (_q21))
                      {
                        {
/* #line 5976 "../../gcc/match.pd" */
                          tree captures[3] ATTRIBUTE_UNUSED = { _p0, _q20, _q21 };
                          if (gimple_simplify_256 (res_op, seq, valueize, type, captures))
                            return true;
                        }
                      }
                    if (integer_nonzerop (_q20))
                      {
                        {
/* #line 5976 "../../gcc/match.pd" */
                          tree captures[3] ATTRIBUTE_UNUSED = { _p0, _q21, _q20 };
                          if (gimple_simplify_256 (res_op, seq, valueize, type, captures))
                            return true;
                        }
                      }
                  }
Though, sure, I should test it in the testcase too.
Here is what I've committed as obvious after testing on x86_64-linux
-m32/-m64:

2022-06-02  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/30314
	* gcc.dg/tree-ssa/pr30314.c: Add tests with swapped arguments.

--- gcc/testsuite/gcc.dg/tree-ssa/pr30314.c.jj	2022-06-01 17:54:30.000000000 +0200
+++ gcc/testsuite/gcc.dg/tree-ssa/pr30314.c	2022-06-02 11:01:27.818987766 +0200
@@ -4,6 +4,8 @@
 /* { dg-final { scan-tree-dump-not "\.MUL_OVERFLOW " "optimized" } } */
 /* { dg-final { scan-tree-dump " > 122713351" "optimized" { target int32 } } } */
 /* { dg-final { scan-tree-dump " > 527049830677415760" "optimized" { target lp64 } } } */
+/* { dg-final { scan-tree-dump " > 102261126" "optimized" { target int32 } } } */
+/* { dg-final { scan-tree-dump " > 439208192231179800" "optimized" { target lp64 } } } */
 
 int
 foo (unsigned int x)
@@ -16,3 +18,15 @@ bar (unsigned long int x)
 {
   return __builtin_mul_overflow_p (x, 35UL, 0UL);
 }
+
+int
+baz (unsigned int x)
+{
+  return __builtin_mul_overflow_p (42, x, 0U);
+}
+
+int
+qux (unsigned long int x)
+{
+  return __builtin_mul_overflow_p (42, x, 0UL);
+}


	Jakub