re PR tree-optimization/87546 (Gcc miscompiles at -O3 on valid code)

	PR tree-optimization/87546
	* tree-vect-patterns.c (vect_look_through_possible_promotion): Add
	min_precision variable, initially set it to orig_precision, only does
	something if op_type's precision is <= min_precision and update
	min_precision whenever calling set_op.

	* gcc.dg/vect/O3-pr87546.c: New test.

From-SVN: r266237

gcc/ChangeLog

+2018-11-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/87546
+	* tree-vect-patterns.c (vect_look_through_possible_promotion): Add
+	min_precision variable, initially set it to orig_precision, only does
+	something if op_type's precision is <= min_precision and update
+	min_precision whenever calling set_op.
+
 2018-11-16  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR ipa/87957

gcc/testsuite/ChangeLog

+2018-11-17  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/87546
+	* gcc.dg/vect/O3-pr87546.c: New test.
+
 2018-11-17  Jozef Lawrynowicz  <jozef.l@mittosystems.com>
 
 	PR middle-end/87854

gcc/testsuite/gcc.dg/vect/O3-pr87546.c

+#include "tree-vect.h"
+
+int a;
+long b, f;
+signed char c, g;
+short int d = 219;
+int e[64];
+
+__attribute__((noipa)) void
+foo (void)
+{
+  asm volatile ("" : : "g" (&a), "g" (&d) : "memory");
+  for (c = 0; c < 64; c++)
+    {
+      g = d < 0 ? d : d >> a;
+      f = g + b;
+      e[c] = f;
+    }
+  if (e[1] != (signed char) d)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  check_vect ();
+  foo ();
+  return 0;
+}

gcc/tree-vect-patterns.c

@@ -367,6 +367,7 @@ vect_look_through_possible_promotion (vec_info *vinfo, tree op,
   tree res = NULL_TREE;
   tree op_type = TREE_TYPE (op);
   unsigned int orig_precision = TYPE_PRECISION (op_type);
+  unsigned int min_precision = orig_precision;
   stmt_vec_info caster = NULL;
   while (TREE_CODE (op) == SSA_NAME && INTEGRAL_TYPE_P (op_type))
     {
@@ -385,7 +386,7 @@ vect_look_through_possible_promotion (vec_info *vinfo, tree op,
 	 This copes with cases such as the result of an arithmetic
 	 operation being truncated before being stored, and where that
 	 arithmetic operation has been recognized as an over-widened one.  */
-      if (TYPE_PRECISION (op_type) <= orig_precision)
+      if (TYPE_PRECISION (op_type) <= min_precision)
 	{
 	  /* Use OP as the UNPROM described above if we haven't yet
 	     found a promotion, or if using the new input preserves the
@@ -393,7 +394,10 @@ vect_look_through_possible_promotion (vec_info *vinfo, tree op,
 	  if (!res
 	      || TYPE_PRECISION (unprom->type) == orig_precision
 	      || TYPE_SIGN (unprom->type) == TYPE_SIGN (op_type))
-	    unprom->set_op (op, dt, caster);
+	    {
+	      unprom->set_op (op, dt, caster);
+	      min_precision = TYPE_PRECISION (op_type);
+	    }
 	  /* Stop if we've already seen a promotion and if this
 	     conversion does more than change the sign.  */
 	  else if (TYPE_PRECISION (op_type)