[PATCH] c++: Readd [LR]ROTATE_EXPR support to constexpr.c [PR94067]

[Jakub Jelinek]

Hi!

Since r10-6527-gaaa26bf496a646778ac861aed124d960b5bf549f fold_for_warn
will perform maybe_constant_value even on some cp_fold produced trees and
so can include rotate exprs which were removed last fall from constexpr.c

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2020-03-06  Jakub Jelinek  <jakub@redhat.com>

	PR c++/94067
	Revert
	2019-10-11  Paolo Carlini  <paolo.carlini@oracle.com>

	* constexpr.c (cxx_eval_constant_expression): Do not handle
	RROTATE_EXPR and LROTATE_EXPR.

	* g++.dg/warn/Wconversion-pr94067.C: New test.

--- gcc/cp/constexpr.c.jj	2020-03-05 07:58:02.578137680 +0100
+++ gcc/cp/constexpr.c	2020-03-06 11:55:27.126682726 +0100
@@ -5730,6 +5730,8 @@ cxx_eval_constant_expression (const cons
     case MAX_EXPR:
     case LSHIFT_EXPR:
     case RSHIFT_EXPR:
+    case LROTATE_EXPR:
+    case RROTATE_EXPR:
     case BIT_IOR_EXPR:
     case BIT_XOR_EXPR:
     case BIT_AND_EXPR:
@@ -7853,6 +7855,8 @@ potential_constant_expression_1 (tree t,
     case MAX_EXPR:
     case LSHIFT_EXPR:
     case RSHIFT_EXPR:
+    case LROTATE_EXPR:
+    case RROTATE_EXPR:
     case BIT_IOR_EXPR:
     case BIT_XOR_EXPR:
     case BIT_AND_EXPR:
--- gcc/testsuite/g++.dg/warn/Wconversion-pr94067.C.jj	2020-03-06 11:57:08.335191087 +0100
+++ gcc/testsuite/g++.dg/warn/Wconversion-pr94067.C	2020-03-06 11:59:55.843722307 +0100
@@ -0,0 +1,9 @@
+// PR c++/94067
+// { dg-do compile }
+// { dg-options "-Wconversion" }
+
+static inline unsigned short
+swap (unsigned short x)
+{
+  return (x >> 8) | static_cast<unsigned short>(x << 8);
+}

	Jakub