[gcc r14-8742] tree-ssa-math-opts: Fix is_widening_mult_rhs_p - unbreak bootstrap [PR113705]

[gcc r14-8742] tree-ssa-math-opts: Fix is_widening_mult_rhs_p - unbreak bootstrap [PR113705]

[Jakub Jelinek]

https://gcc.gnu.org/g:a8f335ccb61bf6105192a4197ef2d84900614dc1

commit r14-8742-ga8f335ccb61bf6105192a4197ef2d84900614dc1
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Feb 2 11:25:13 2024 +0100

    tree-ssa-math-opts: Fix is_widening_mult_rhs_p - unbreak bootstrap [PR113705]
    
    On Tue, Jan 30, 2024 at 07:33:10AM -0000, Roger Sayle wrote:
    +             wide_int bits = wide_int::from (tree_nonzero_bits (rhs),
    +                                             prec,
    +                                             TYPE_SIGN (TREE_TYPE (rhs)));
    ...
    > +               if (gimple_assign_rhs_code (stmt) == BIT_AND_EXPR
    > +                   && TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST
    > +                   && wi::to_wide (gimple_assign_rhs2 (stmt))
    > +                      == wi::mask (hprec, false, prec))
    
    This change broke bootstrap on aarch64-linux.
    The problem can be seen even on the reduced testcase.
    
    The IL on the unreduced testcase before widening_mul has:
      # val_583 = PHI <val_26(13), val_164(40)>
    ...
      pretmp_266 = MEM[(const struct wide_int_storage *)&D.160657].len;
      _264 = pretmp_266 & 65535;
    ...
      _176 = (sizetype) val_583;
      _439 = (sizetype) _264;
      _284 = _439 * 8;
      _115 = _176 + _284;
    where 583/266/264 have unsigned int type and 176/439/284/115 have sizetype.
    widening_mul first turns that into:
      # val_583 = PHI <val_26(13), val_164(40)>
    ...
      pretmp_266 = MEM[(const struct wide_int_storage *)&D.160657].len;
      _264 = pretmp_266 & 65535;
    ...
      _176 = (sizetype) val_583;
      _439 = (sizetype) _264;
      _284 = _264 w* 8;
      _115 = _176 + _284;
    and then is_widening_mult_rhs_p is called, with type sizetype (64-bit),
    rhs _264, hprec 32 and prec 64.  Now tree_nonzero_bits (rhs) is
    65535, so bits is 64-bit wide_int 65535, stmt is BIT_AND_EXPR,
    but we ICE on the
    wi::to_wide (gimple_assign_rhs2 (stmt)) == wi::mask (hprec, false, prec)
    comparison because wi::to_wide on gimple_assign_rhs2 (stmt) - unsigned int
    65535 gives 32-bit wide_int 65535, while wi::mask (hprec, false, prec)
    gives 64-bit wide_int 0xffffffff and comparison between different precision
    wide_ints is forbidden.
    
    The following patch fixes it the same way how bits is computed earlier,
    by calling wide_int::from on the wi::to_wide (gimple_assign_rhs2 (stmt)),
    so we compare 64-bit 65535 with 64-bit 0xffffffff.
    
    2024-02-02  Jakub Jelinek  <jakub@redhat.com>
    
            PR middle-end/113705
            * tree-ssa-math-opts.cc (is_widening_mult_rhs_p): Use wide_int_from
            around wi::to_wide in order to compare value in prec precision.
    
            * g++.dg/opt/pr113705.C: New test.

Diff:
---
 gcc/testsuite/g++.dg/opt/pr113705.C | 68 +++++++++++++++++++++++++++++++++++++
 gcc/tree-ssa-math-opts.cc           |  3 +-
 2 files changed, 70 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/g++.dg/opt/pr113705.C b/gcc/testsuite/g++.dg/opt/pr113705.C
new file mode 100644
index 000000000000..39fb047077ef
--- /dev/null
+++ b/gcc/testsuite/g++.dg/opt/pr113705.C
@@ -0,0 +1,68 @@
+// PR middle-end/113705
+// { dg-do compile { target c++17 } }
+// { dg-options "-O2 -w" }
+
+void foo ();
+template <typename T> struct A : T { long bar () const; };
+int a;
+
+template <typename T>
+long
+A<T>::bar () const
+{
+  return this->baz ()[a];
+}
+
+struct B {
+  struct { long b[1]; long c; } u;
+  unsigned d;
+  int e;
+  B (const B &);
+  ~B ();
+  const long *baz () const;
+  unsigned qux () const;
+};
+
+B::B (const B &)
+{
+  if (__builtin_expect (e, 0))
+    u.c = 0;
+}
+
+B::~B ()
+{
+  if (__builtin_expect (e, 0))
+    foo ();
+}
+
+const long *
+B::baz () const
+{
+  return u.b;
+}
+
+unsigned
+B::qux () const
+{
+  return d;
+}
+
+struct C { A<B> corge () const; A<B> *f; };
+
+A<B>
+C::corge () const
+{
+  return f[1];
+}
+
+void
+test (C r, long *h, unsigned short *d)
+{
+  for (int j = 0; j < 8; ++j)
+    {
+      A g = r.corge ();
+      *d = g.qux ();
+      for (unsigned i = 0; i < *d; ++i)
+	*h++ = g.bar ();
+    }
+}
diff --git a/gcc/tree-ssa-math-opts.cc b/gcc/tree-ssa-math-opts.cc
index cffe7573f794..aa9f7b579994 100644
--- a/gcc/tree-ssa-math-opts.cc
+++ b/gcc/tree-ssa-math-opts.cc
@@ -2572,7 +2572,8 @@ is_widening_mult_rhs_p (tree type, tree rhs, tree *type_out,
 	      if (is_gimple_assign (stmt)
 		  && gimple_assign_rhs_code (stmt) == BIT_AND_EXPR
 		  && TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST
-		  && wi::to_wide (gimple_assign_rhs2 (stmt))
+		  && wide_int::from (wi::to_wide (gimple_assign_rhs2 (stmt)),
+				     prec, TYPE_SIGN (TREE_TYPE (rhs)))
 		     == wi::mask (hprec, false, prec))
 		*new_rhs_out = gimple_assign_rhs1 (stmt);
 	      else