tree-optimization/95308 - really avoid forward propagating of &TMR

This fixes a hole that still allowed forwarding of TARGET_MEM_REF
addresses.

2020-05-25  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/95308
	* tree-ssa-forwprop.c (pass_forwprop::execute): Generalize
	test for TARGET_MEM_REFs.

	* g++.dg/torture/pr95308.C: New testcase.

gcc/testsuite/g++.dg/torture/pr95308.C

+// { dg-do compile }
+// { dg-additional-options "-march=skylake-avx512" { target x86_64-*-* i?86-*-* } }
+
+extern int a[][18];
+extern short b[], c[];
+extern char d[][18];
+int e;
+void i(char f, long g[][100][100][100])
+{
+  for (int h = 0;; h += 2)
+    for (char j = 0; j < 17; j++) {
+	if (e ? f : 0) {
+	    a[h][j] = 5;
+	    for (int k = 0; k < 12; k += 4)
+	      for (short l = 0; l < 015; l += 2)
+		b[k * 3 + l] = bool(g[2][j][k][l]);
+	} else
+	  d[h][j] = 0;
+	c[j] = 3;
+    }
+}

gcc/tree-ssa-forwprop.c

@@ -2771,18 +2771,18 @@ pass_forwprop::execute (function *fun)
 
 	  /* If this statement sets an SSA_NAME to an address,
 	     try to propagate the address into the uses of the SSA_NAME.  */
-	  if (code == ADDR_EXPR
+	  if ((code == ADDR_EXPR
 	       /* Handle pointer conversions on invariant addresses
 		  as well, as this is valid gimple.  */
 	       || (CONVERT_EXPR_CODE_P (code)
 		   && TREE_CODE (rhs) == ADDR_EXPR
 		   && POINTER_TYPE_P (TREE_TYPE (lhs))))
+	      && TREE_CODE (TREE_OPERAND (rhs, 0)) != TARGET_MEM_REF)
 	    {
 	      tree base = get_base_address (TREE_OPERAND (rhs, 0));
 	      if ((!base
 		   || !DECL_P (base)
 		   || decl_address_invariant_p (base))
-		  && TREE_CODE (base) != TARGET_MEM_REF
 		  && !stmt_references_abnormal_ssa_name (stmt)
 		  && forward_propagate_addr_expr (lhs, rhs, true))
 		{