diff mbox series

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

Message ID ZbwfF+oAgCCq002P@tucnak
State Unresolved
Headers
Series tree-ssa-math-opts: Fix is_widening_mult_rhs_p - unbreak bootstrap [PR113705] |

Checks

Context Check Description
snail/gcc-patch-check warning Git am fail log

Commit Message

Jakub Jelinek Feb. 1, 2024, 10:45 p.m. UTC 
  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.

Bootstrapped/regtested on x86_64-linux and i686-linux plus tested on the
testcase using cross to aarch64-linux, ok for trunk?

2024-02-01  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.



	Jakub

Comments

Richard Biener Feb. 2, 2024, 10:19 a.m. UTC | #1 
> Am 01.02.2024 um 23:46 schrieb Jakub Jelinek <jakub@redhat.com>:
> 
> 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.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux plus tested on the
> testcase using cross to aarch64-linux, ok for trunk?

Ok

Richard 
> 2024-02-01  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.
> 
> --- gcc/tree-ssa-math-opts.cc.jj    2024-02-01 09:14:16.623549514 +0100
> +++ gcc/tree-ssa-math-opts.cc    2024-02-01 17:48:59.151771177 +0100
> @@ -2572,7 +2572,8 @@ is_widening_mult_rhs_p (tree type, tree
>          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
> --- gcc/testsuite/g++.dg/opt/pr113705.C.jj    2024-02-01 19:02:29.181388575 +0100
> +++ gcc/testsuite/g++.dg/opt/pr113705.C    2024-02-01 19:03:03.211918152 +0100
> @@ -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 ();
> +    }
> +}
> 
> 
>    Jakub
>
diff mbox series

Patch

--- gcc/tree-ssa-math-opts.cc.jj	2024-02-01 09:14:16.623549514 +0100
+++ gcc/tree-ssa-math-opts.cc	2024-02-01 17:48:59.151771177 +0100
@@ -2572,7 +2572,8 @@  is_widening_mult_rhs_p (tree type, tree
 	      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
--- gcc/testsuite/g++.dg/opt/pr113705.C.jj	2024-02-01 19:02:29.181388575 +0100
+++ gcc/testsuite/g++.dg/opt/pr113705.C	2024-02-01 19:03:03.211918152 +0100
@@ -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 ();
+    }
+}