[PATCH] Fix (ocvt (icvt at 1 @0)) simplification (PR tree-optimization/66233)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

We ICE on the following testcase at -O3 on x86_64-linux, because
gimple folding attempts to simplify FLOAT_EXPR conversion of
signed V4SI to V4SF feeding FIX_TRUNC_EXPR to unsigned V4SI
into a FIX_TRUNC_EXPR with unsigned V4SI lhs and signed V4SI rhs1,
which is invalid GIMPLE.
All the other simplifications in the same iterator block don't
optimize anything for vector types, and I can't find out any case
where something like this would be beneficial for vector types.
These days we represent source level casts of vectors to same sized
integers as VIEW_CONVERT_EXPR, which isn't handled in here,
and *_prec doesn't really mean what it tests for vector types
(it is log2 of number of elements), vector integer or float widening
is not represented using convert/float/fix_trunc, but using VEC_PERM_EXPR,
VEC_UNPACK*_{LO,HI}_EXPR etc.
I've bootstrapped/regtested with a logging variant and if
(inside_vec || inter_vec || final_vec) is true, we (mis)optimize
anything only on the testcase included in the patch and on
gfortran.dg/stfunc_4.f90 testcase, in both cases it is
V4SI -> V4SF -> V4SI, which we really shouldn't be optimizing,
because SF mode obviously can't represent all integers exactly.

So, this patch disables optimizing vectors.
Ok for trunk/5.2 if bootstrap/regtest succeeds?

For 4.9/4.8 a similar patch will be needed, but to
fold-const.c/tree-ssa-forwprop.c instead of match.pd.

2015-05-21  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/66233
	* match.pd (ocvt (icvt@1 @0)): Don't handle vector types.
	Simplify.

	* gcc.c-torture/execute/pr66233.c: New test.

--- gcc/match.pd.jj	2015-05-19 15:53:43.000000000 +0200
+++ gcc/match.pd	2015-05-21 16:21:35.627916502 +0200
@@ -730,16 +730,12 @@ (define_operator_list inverted_tcc_compa
       (for integers).  Avoid this if the final type is a pointer since
       then we sometimes need the middle conversion.  Likewise if the
       final type has a precision not equal to the size of its mode.  */
-   (if (((inter_int && inside_int)
-	 || (inter_float && inside_float)
-	 || (inter_vec && inside_vec))
+   (if (((inter_int && inside_int) || (inter_float && inside_float))
+	&& (final_int || final_float)
 	&& inter_prec >= inside_prec
-	&& (inter_float || inter_vec
-	    || inter_unsignedp == inside_unsignedp)
-	&& ! (final_prec != GET_MODE_PRECISION (element_mode (type))
-	      && element_mode (type) == element_mode (inter_type))
-	&& ! final_ptr
-	&& (! final_vec || inter_prec == inside_prec))
+	&& (inter_float || inter_unsignedp == inside_unsignedp)
+	&& ! (final_prec != GET_MODE_PRECISION (TYPE_MODE (type))
+	      && TYPE_MODE (type) == TYPE_MODE (inter_type)))
     (ocvt @0))
 
    /* If we have a sign-extension of a zero-extended value, we can
--- gcc/testsuite/gcc.c-torture/execute/pr66233.c.jj	2015-05-21 17:13:32.639713225 +0200
+++ gcc/testsuite/gcc.c-torture/execute/pr66233.c	2015-05-21 17:10:57.000000000 +0200
@@ -0,0 +1,22 @@
+/* PR tree-optimization/66233 */
+
+unsigned int v[8];
+
+__attribute__((noinline, noclone)) void
+foo (void)
+{
+  int i;
+  for (i = 0; i < 8; i++)
+    v[i] = (float) i;
+}
+
+int
+main ()
+{
+  unsigned int i;
+  foo ();
+  for (i = 0; i < 8; i++)
+    if (v[i] != i)
+      __builtin_abort ();
+  return 0;
+}

	Jakub