[PATCH] Fix powerpc* ICE with vec builtins with -mno-altivec (PR target/82848)

[Jakub Jelinek <jakub@redhat.com>]

Hi!

With -mno-altivec -mno-vsx -mno-fold-gimple we error on __builtin_vec*
builtins used when corresponding ISA is not enabled.
When folding gimple, in some cases we get away with it (e.g. when folding
the builtin to PLUS_EXPR on the generic vectors), because
tree-vect-generic.c lowers those into scalar piecewise operations,
but e.g. in case of FMA_EXPR tree-vect-generic.c isn't doing anything,
expects that FMA_EXPR is actually used only if supported, I think similarly
for various vector widening operations etc.

One option is not to fold into gimple only those builtins where we know it
will not work on generic vectors; my preference is to not fold any builtin
which would be rejected at expansion time, so user get at least consistent
diagnostics.  Usually people are using the altivec.h etc. headers that error
if the ISA is not enabled, so this will only affect people that use the
builtins directly.

Bootstrapped/regtested on powerpc64{,le}-linux, ok for trunk?

2017-11-23  Jakub Jelinek  <jakub@redhat.com>

	PR target/82848
	* config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Don't fold
	builtins not enabled in the currently selected ISA.

--- gcc/config/rs6000/rs6000.c.jj	2017-11-23 10:29:01.000000000 +0100
+++ gcc/config/rs6000/rs6000.c	2017-11-23 10:30:54.930019590 +0100
@@ -16143,6 +16143,12 @@ rs6000_gimple_fold_builtin (gimple_stmt_
   if (!gimple_call_lhs (stmt) && !rs6000_builtin_valid_without_lhs (fn_code))
     return false;

+  /* Don't fold invalid builtins, let rs6000_expand_builtin diagnose it.  */
+  HOST_WIDE_INT mask = rs6000_builtin_info[uns_fncode].mask;
+  bool func_valid_p = (rs6000_builtin_mask & mask) == mask;
+  if (!func_valid_p)
+    return false;
+
   switch (fn_code)
     {
     /* Flavors of vec_add.  We deliberately don't expand
--- gcc/testsuite/gcc.target/powerpc/pr82848.c.jj	2017-11-23 10:34:14.670471607 +0100
+++ gcc/testsuite/gcc.target/powerpc/pr82848.c	2017-11-23 10:36:22.754841465 +0100
@@ -0,0 +1,13 @@
+/* PR target/82848 */
+/* { dg-do compile } */
+/* { dg-options "-mno-altivec -mno-vsx -Wno-psabi" } */
+
+#define C 3.68249351546114573519399405666776E-44f
+#define vector __attribute__ ((altivec (vector__)))
+
+vector float
+foo (vector float a)
+{
+  vector float b = __builtin_vec_madd (b, a, (vector float) { C, C, C, C });	/* { dg-error "requires the '-maltivec' option" } */
+  return b;
+}

	Jakub