[PATCH] unswitch: Fold case label lo/hi values to index type [PR105770]

[Jakub Jelinek via Gcc-patches]

Hi!

The following testcase ICEs because we use different types in comparison,
idx has int type, while CASE_LOW has char type.

While I believe all CASE_{LOW,HIGH} in the same switch have to use the same
or compatible type, the index expression can have a promoted type as happens
in this testcase.  Other spots that handle switches do such foldings too.

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

2022-05-31  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/105770
        * tree-ssa-loop-unswitch.cc (find_unswitching_predicates_for_bb): Cast
        CASE_LOW and CASE_HIGH to TREE_TYPE (idx) before comparisons with idx.

        * gcc.dg/pr105770.c: New test.

--- gcc/tree-ssa-loop-unswitch.cc.jj    2022-05-25 11:07:29.754185772 +0200
+++ gcc/tree-ssa-loop-unswitch.cc       2022-05-30 10:57:23.165131441 +0200
@@ -494,6 +494,7 @@ find_unswitching_predicates_for_bb (basi
     {
       unsigned nlabels = gimple_switch_num_labels (stmt);
       tree idx = gimple_switch_index (stmt);
+      tree idx_type = TREE_TYPE (idx);
       if (TREE_CODE (idx) != SSA_NAME
          || nlabels < 1)
        return;
@@ -526,16 +527,18 @@ find_unswitching_predicates_for_bb (basi
          if (CASE_HIGH (lab) != NULL_TREE)
            {
              tree cmp1 = fold_build2 (GE_EXPR, boolean_type_node, idx,
-                                      CASE_LOW (lab));
+                                      fold_convert (idx_type,
+                                                    CASE_LOW (lab)));
              tree cmp2 = fold_build2 (LE_EXPR, boolean_type_node, idx,
-                                      CASE_HIGH (lab));
+                                      fold_convert (idx_type,
+                                                    CASE_HIGH (lab)));
              cmp = fold_build2 (BIT_AND_EXPR, boolean_type_node, cmp1, cmp2);
              lab_range.set (CASE_LOW (lab), CASE_HIGH (lab));
            }
          else
            {
              cmp = fold_build2 (EQ_EXPR, boolean_type_node, idx,
-                                CASE_LOW (lab));
+                                fold_convert (idx_type, CASE_LOW (lab)));
              lab_range.set (CASE_LOW (lab));
            }
 
--- gcc/testsuite/gcc.dg/pr105770.c.jj  2022-05-30 11:08:30.603530499 +0200
+++ gcc/testsuite/gcc.dg/pr105770.c     2022-05-30 11:07:12.066406193 +0200
@@ -0,0 +1,19 @@
+/* PR tree-optimization/105770 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -funswitch-loops -fno-tree-forwprop" } */
+
+char a;
+
+void
+foo (void)
+{
+  while (a)
+    switch (a)
+      {
+      case ' ':
+      case '\t':
+       return;
+      }
+
+  __builtin_unreachable ();
+}

        Jakub