expand: Fix up expand_cond_expr_using_cmove [PR106030]

If expand_cond_expr_using_cmove can't find a cmove optab for a particular
mode, it tries to promote the mode and perform the cmove in the promoted
mode.

The testcase in the patch ICEs on arm because in that case we pass temp which
has the promoted mode (SImode) as target to expand_operands where the
operands have the non-promoted mode (QImode).
Later on the function uses paradoxical subregs:
  if (GET_MODE (op1) != mode)
    op1 = gen_lowpart (mode, op1);

  if (GET_MODE (op2) != mode)
    op2 = gen_lowpart (mode, op2);
to change the operand modes.

The following patch fixes it by passing NULL_RTX as target if it has
promoted mode.

2022-06-21  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/106030
	* expr.c (expand_cond_expr_using_cmove): Pass NULL_RTX instead of
	temp to expand_operands if mode has been promoted.

	* gcc.c-torture/compile/pr106030.c: New test.

(cherry picked from commit 2df1df945fac85d7b3d084001414a66a2709d8fe)

diff --git a/gcc/expr.c b/gcc/expr.c
index dabee8142400ce83f88d4030c536e2506536b07c..a904b4c978534886fc4950a83fc0f67a9b958e5d 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -8411,7 +8411,8 @@ expand_cond_expr_using_cmove (tree treeop0 ATTRIBUTE_UNUSED,
   expanding_cond_expr_using_cmove = true;
   start_sequence ();
   expand_operands (treeop1, treeop2,
-                  temp, &op1, &op2, EXPAND_NORMAL);
+                  mode == orig_mode ? temp : NULL_RTX, &op1, &op2,
+                  EXPAND_NORMAL);
 
   if (TREE_CODE (treeop0) == SSA_NAME
       && (srcstmt = get_def_for_expr_class (treeop0, tcc_comparison)))

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr106030.c b/gcc/testsuite/gcc.c-torture/compile/pr106030.c
new file mode 100644 (file)
index 0000000..7514b34
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr106030.c
@@ -0,0 +1,16 @@
+/* PR middle-end/106030 */
+
+int a, b, c;
+
+char
+foo (int x, int y)
+{
+  return x * y;
+}
+
+void
+bar (void)
+{
+  char d = (foo <= b) * a;
+  c = foo (2 != bar, d);
+}