[PATCH] match: Simplify double not and double negate to a non_lvalue

[Mikael Morin]

From: Mikael Morin <mik...@gcc.gnu.org>

Regression tested on x86_64-linux.  OK for master?

-- 8< --

gcc/ChangeLog:

        * match.pd (`-(-X)`, `~(~X)`): Add a NON_LVALUE_EXPR wrapper to the
        simplification of doubled unary operators NEGATE_EXPR and
        BIT_NOT_EXPR.

gcc/testsuite/ChangeLog:

        * gfortran.dg/non_lvalue_1.f90: New test.
---
 gcc/match.pd                               |  4 ++--
 gcc/testsuite/gfortran.dg/non_lvalue_1.f90 | 23 ++++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gfortran.dg/non_lvalue_1.f90

diff --git a/gcc/match.pd b/gcc/match.pd
index 0f53c162fce..ad0fa8f1004 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -2357,7 +2357,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
 /* ~~x -> x */
 (simplify
   (bit_not (bit_not @0))
-  @0)
+  (non_lvalue @0))
 
 /* zero_one_valued_p will match when a value is known to be either
    0 or 1 including constants 0 or 1.
@@ -4037,7 +4037,7 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
   (negate (nop_convert? (negate @1)))
   (if (!TYPE_OVERFLOW_SANITIZED (type)
        && !TYPE_OVERFLOW_SANITIZED (TREE_TYPE (@1)))
-   (view_convert @1)))
+   (non_lvalue (view_convert @1))))
 
  /* We can't reassociate floating-point unless -fassociative-math
     or fixed-point plus or minus because of saturation to +-Inf.  */
diff --git a/gcc/testsuite/gfortran.dg/non_lvalue_1.f90 
b/gcc/testsuite/gfortran.dg/non_lvalue_1.f90
new file mode 100644
index 00000000000..536c86b1eb6
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/non_lvalue_1.f90
@@ -0,0 +1,23 @@
+! { dg-do compile }
+! { dg-additional-options "-fdump-tree-original" }
+!
+! Check the generation of NON_LVALUE_EXPR expressions in cases where a unary
+! operator expression would simplify to a bare data reference.
+
+! A NON_LVALUE_EXPR is generated for a double negation that would simplify to
+! a bare data reference.
+function f1 (f1_arg1)
+  integer, value :: f1_arg1
+  integer :: f1
+  f1 = -(-f1_arg1)
+end function
+! { dg-final { scan-tree-dump "__result_f1 = NON_LVALUE_EXPR <f1_arg1>;" 
"original" } }
+
+! A NON_LVALUE_EXPR is generated for a double complement that would simplify to
+! a bare data reference.
+function f2 (f2_arg1)
+  integer, value :: f2_arg1
+  integer :: f2
+  f2 = not(not(f2_arg1))
+end function
+! { dg-final { scan-tree-dump "__result_f2 = NON_LVALUE_EXPR <f2_arg1>;" 
"original" } }
-- 
2.47.2