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

[Richard Biener <rguenther at suse dot de>]

On May 21, 2015 5:28:14 PM GMT+02:00, Jakub Jelinek <jakub@redhat.com> wrote:
>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?

OK.

Thanks,
Richard.

>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