tree-optimization/104700 - adjust constant handling in PRE

The following refactors find_or_generate_expression to more properly
handle constant valued SSA names thereby simplifying the code and
avoiding ICEing after the last change to NARY processing.

2022-02-28  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/104700
	* tree-ssa-pre.cc (get_or_alloc_expr_for): Remove and inline
	into ...
	(find_or_generate_expression): ... here, simplifying code.

	* gcc.dg/pr104700-2.c: New testcase.
	* gcc.dg/torture/pr104700-1.c: Likewise.

gcc/testsuite/gcc.dg/pr104700-2.c

@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-ccp -fno-tree-dce -fno-tree-vrp" } */
+
+int a, b;
+int main() {
+  int c = 2, d, e = 0;
+  if (a)
+    e = 2;
+  int f, g = -(1L | (e && f && f & e));
+  if (g)
+  L:
+    g = c;
+  c = 0;
+  d = e * g;
+  if (d)
+    goto L;
+  while (e) {
+    int i = (a && b) * i;
+  }
+  return 0;
+}

gcc/testsuite/gcc.dg/torture/pr104700-1.c

@@ -0,0 +1,38 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ftree-pre" } */
+
+int printf(const char *, ...);
+int a, b, c = 2, d, e, *f, g;
+void o() {
+  unsigned h = 1;
+  int j = -1, k, l = 1, m = 2, i;
+  while (c < 2)
+    ;
+L1:
+  k = h;
+  h = -1;
+  if (k < 2 && !c) {
+    printf("%d", k);
+    goto L1;
+  }
+  if (!j)
+    l = printf("0");
+  if (g)
+    k = 0;
+  if (a && k)
+    goto L2;
+  while (f) {
+    m = a;
+    d = i;
+    i = e;
+    f = &j;
+  L2:
+    if (d == l && !m)
+      l = b;
+  }
+  unsigned *n[1] = {&h};
+}
+int main() {
+  o();
+  return 0;
+}

gcc/tree-ssa-pre.cc

@@ -1197,18 +1197,6 @@ get_or_alloc_expr_for_constant (tree constant)
   return newexpr;
 }
 
-/* Get or allocate a pre_expr for a piece of GIMPLE, and return it.
-   Currently only supports constants and SSA_NAMES.  */
-static pre_expr
-get_or_alloc_expr_for (tree t)
-{
-  if (TREE_CODE (t) == SSA_NAME)
-    return get_or_alloc_expr_for_name (t);
-  else if (is_gimple_min_invariant (t))
-    return get_or_alloc_expr_for_constant (t);
-  gcc_unreachable ();
-}
-
 /* Return the folded version of T if T, when folded, is a gimple
    min_invariant or an SSA name.  Otherwise, return T.  */
 
@@ -2779,8 +2767,16 @@ create_component_ref_by_pieces (basic_block block, vn_reference_t ref,
 static tree
 find_or_generate_expression (basic_block block, tree op, gimple_seq *stmts)
 {
-  pre_expr expr = get_or_alloc_expr_for (op);
-  unsigned int lookfor = get_expr_value_id (expr);
+  /* Constants are always leaders.  */
+  if (is_gimple_min_invariant (op))
+    return op;
+
+  gcc_assert (TREE_CODE (op) == SSA_NAME);
+  vn_ssa_aux_t info = VN_INFO (op);
+  unsigned int lookfor = info->value_id;
+  if (value_id_constant_p (lookfor))
+    return info->valnum;
+
   pre_expr leader = bitmap_find_leader (AVAIL_OUT (block), lookfor);
   if (leader)
     {
@@ -2808,7 +2804,7 @@ find_or_generate_expression (basic_block block, tree op, gimple_seq *stmts)
 	 its operand values.  */
       if (temp->kind == NARY)
 	return create_expression_by_pieces (block, temp, stmts,
-					    get_expr_type (expr));
+					    TREE_TYPE (op));
     }
 
   /* Defer.  */