ranger: Fix up REALPART_EXPR/IMAGPART_EXPR handling [PR104604]

The following testcase is miscompiled since r12-3328.
That change assumed that if rhs1 of a GIMPLE_ASSIGN is COMPLEX_CST, then
that is the value of the lhs of the stmt, but that is not the case always,
only if it is a GIMPLE_SINGLE_RHS stmt.  If it is e.g.
GIMPLE_UNARY_RHS or GIMPLE_BINARY_RHS (the latter happens in the testcase),
then it can be e.g.
__complex__ (3, 0) / var
and the REALPART_EXPR of that isn't 3, but the realpart of the division.
I assume once the ranger can do complex numbers adjust_*part_expr will just
fetch one or the other range from a underlying complex range, but until
then, we should limit this to what r12-3328 meant to do.

2022-02-22  Jakub Jelinek  <[email protected]>

	PR tree-optimization/104604
	* gimple-range-fold.cc (adjust_imagpart_expr, adjust_realpart_expr):
	Only check if gimple_assign_rhs1 is COMPLEX_CST if
	gimple_assign_rhs_code is COMPLEX_CST.

	* gcc.c-torture/execute/pr104604.c: New test.

gcc/gimple-range-fold.cc

@@ -397,7 +397,8 @@ adjust_imagpart_expr (irange &res, const gimple *stmt)
 	}
       return;
     }
-  if (is_gimple_assign (def_stmt))
+  if (is_gimple_assign (def_stmt)
+      && gimple_assign_rhs_code (def_stmt) == COMPLEX_CST)
     {
       tree cst = gimple_assign_rhs1 (def_stmt);
       if (TREE_CODE (cst) == COMPLEX_CST)
@@ -422,7 +423,8 @@ adjust_realpart_expr (irange &res, const gimple *stmt)
   if (!SSA_NAME_DEF_STMT (name))
     return;
 
-  if (is_gimple_assign (def_stmt))
+  if (is_gimple_assign (def_stmt)
+      && gimple_assign_rhs_code (def_stmt) == COMPLEX_CST)
     {
       tree cst = gimple_assign_rhs1 (def_stmt);
       if (TREE_CODE (cst) == COMPLEX_CST)

gcc/testsuite/gcc.c-torture/execute/pr104604.c

@@ -0,0 +1,34 @@
+/* PR tree-optimization/104604 */
+
+unsigned char g;
+
+__attribute__((noipa))
+unsigned char
+foo (_Complex unsigned c)
+{
+  unsigned char v = g;
+  _Complex unsigned t = 3;
+  t /= c;
+  return v + t;
+}
+
+__attribute__((noipa))
+unsigned char
+bar (_Complex unsigned c)
+{
+  unsigned char v = g;
+  _Complex unsigned t = 42;
+  t /= c;
+  return v + t;
+}
+
+int
+main ()
+{
+  unsigned char x = foo (7);
+  if (x)
+    __builtin_abort ();
+  if (bar (7) != 6)
+    __builtin_abort ();
+  return 0;
+}