[PATCH] Fix factor_out_conditional_conversion caused ICE (PR tree-optimization/83521)

[Jakub Jelinek]

Hi!

The problem here is that the code expects fold_build1 will actually not
fold, because using gimple_build_assign (..., VIEW_CONVERT_EXPR, temp);
is valid only if TREE_CODE (temp) == VIEW_CONVERT_EXPR.
So, either we can replace the fold_build1 with build1, or we should just
use the gimple_build_assign overload that will handle even what
<view_convert_expr <SSA_NAME_result_of_phi>> will fold to (in this case
a <nop_expr <SSA_NAME_result_of_phi>>).

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2017-12-21  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/83521
        * tree-ssa-phiopt.c (factor_out_conditional_conversion): Use
        gimple_build_assign without code on result of
        fold_build1 (VIEW_CONVERT_EXPR, ...), as it might not create
        a VIEW_CONVERT_EXPR.

        * gcc.dg/pr83521.c: New test.

--- gcc/tree-ssa-phiopt.c.jj    2017-12-20 20:40:18.000000000 +0100
+++ gcc/tree-ssa-phiopt.c       2017-12-21 11:25:33.335004838 +0100
@@ -548,8 +548,12 @@ factor_out_conditional_conversion (edge
 
   /* Create the conversion stmt and insert it.  */
   if (convert_code == VIEW_CONVERT_EXPR)
-    temp = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (result), temp);
-  new_stmt = gimple_build_assign (result, convert_code, temp);
+    {
+      temp = fold_build1 (VIEW_CONVERT_EXPR, TREE_TYPE (result), temp);
+      new_stmt = gimple_build_assign (result, temp);
+    }
+  else
+    new_stmt = gimple_build_assign (result, convert_code, temp);
   gsi = gsi_after_labels (gimple_bb (phi));
   gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
 
--- gcc/testsuite/gcc.dg/pr83521.c.jj   2017-12-21 11:29:54.348662949 +0100
+++ gcc/testsuite/gcc.dg/pr83521.c      2017-12-21 11:29:41.000000000 +0100
@@ -0,0 +1,10 @@
+/* PR tree-optimization/83521 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -fno-tree-forwprop" } */
+
+int
+foo (unsigned int x, int y)
+{
+  int *z = (int *)&x;
+  return (y == 0) ? y : *z;
+}

        Jakub