Re: [PATCH] Fix ICE with widen_mult and -ftrapv (PR tree-optimization/83523)

[Richard Biener <rguenther@suse.de>]

On December 21, 2017 6:54:51 PM GMT+01:00, Jakub Jelinek <jakub@redhat.com> wrote:
>Hi!
>
>Converting widening mult, or widen_{plus,minus}_expr, or integral mult
>to
>fma is IMNSHO undesirable with -ftrapv for signed types - the expansion
>of
>those doesn't detect overflows and by giving up we don't need to worry
>about
>formerly trapping MULT_EXPR becoming something that isn't trapping and
>performing EH cleanups etc.
>
>Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK. 

Richard. 

>2017-12-21  Jakub Jelinek  <jakub@redhat.com>
>
>	PR tree-optimization/83523
>	* tree-ssa-math-opts.c (is_widening_mult_p): Return false if
>	for INTEGER_TYPE TYPE_OVERFLOW_TRAPS.
>	(convert_mult_to_fma): Likewise.
>
>	* g++.dg/tree-ssa/pr83523.C: New test.
>
>--- gcc/tree-ssa-math-opts.c.jj	2017-12-21 09:43:19.000000000 +0100
>+++ gcc/tree-ssa-math-opts.c	2017-12-21 12:22:10.576488270 +0100
>@@ -2196,8 +2196,12 @@ is_widening_mult_p (gimple *stmt,
> {
>   tree type = TREE_TYPE (gimple_assign_lhs (stmt));
> 
>-  if (TREE_CODE (type) != INTEGER_TYPE
>-      && TREE_CODE (type) != FIXED_POINT_TYPE)
>+  if (TREE_CODE (type) == INTEGER_TYPE)
>+    {
>+      if (TYPE_OVERFLOW_TRAPS (type))
>+	return false;
>+    }
>+  else if (TREE_CODE (type) != FIXED_POINT_TYPE)
>     return false;
> 
>if (!is_widening_mult_rhs_p (type, gimple_assign_rhs1 (stmt),
>type1_out,
>@@ -2656,7 +2660,7 @@ convert_mult_to_fma (gimple *mul_stmt, t
> 
>   /* We don't want to do bitfield reduction ops.  */
>   if (INTEGRAL_TYPE_P (type)
>-      && !type_has_mode_precision_p (type))
>+      && (!type_has_mode_precision_p (type) || TYPE_OVERFLOW_TRAPS
>(type)))
>     return false;
> 
>/* If the target doesn't support it, don't generate it.  We assume that
>--- gcc/testsuite/g++.dg/tree-ssa/pr83523.C.jj	2017-12-21
>12:20:56.555403891 +0100
>+++ gcc/testsuite/g++.dg/tree-ssa/pr83523.C	2017-12-21
>12:20:02.000000000 +0100
>@@ -0,0 +1,25 @@
>+// PR tree-optimization/83523
>+// { dg-do compile }
>+// { dg-options "-O2 -fexceptions -fnon-call-exceptions -ftrapv" }
>+
>+#ifdef __SIZEOF_INT128__
>+typedef __int128 T;
>+typedef long long int U;
>+#else
>+typedef long long int T;
>+typedef int U;
>+#endif
>+
>+struct S { S (); ~S (); };
>+void bar ();
>+
>+T
>+foo (U x, U y)
>+{
>+  T z = x;
>+  S s;
>+  bar ();
>+  z *= y;
>+  bar ();
>+  return z;
>+}
>
>	Jakub