[gcc(refs/users/mikael/heads/non_lvalue_v02)] match: Simplify double not and double negate to a non_lvalue

[Mikael Morin]

https://gcc.gnu.org/g:c6dab88a696d57401ace4c1b57f33ab785c1431c

commit c6dab88a696d57401ace4c1b57f33ab785c1431c
Author: Mikael Morin <mikael@gcc.gnu.org>
Date:   Thu Jul 4 12:59:34 2024 +0200

    match: Simplify double not and double negate to a non_lvalue
    
    I noticed while testing the second patch that none of the NON_LVALUE_EXPR
    trees I expected were generated when simplifying unary operators, whereas
    they were generated with binary operators.
    
    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.

Diff:
---
 gcc/match.pd                               |  4 ++--
 gcc/testsuite/gfortran.dg/non_lvalue_1.f90 | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gcc/match.pd b/gcc/match.pd
index 0f53c162fce3..ad0fa8f10044 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 000000000000..ac52b2720945
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/non_lvalue_1.f90
@@ -0,0 +1,21 @@
+! { dg-do compile }
+! { dg-additional-options "-fdump-tree-original" }
+!
+! Check the generation of NON_LVALUE_EXPR trees in cases where a unary operator expression
+! simplifies to a data reference.
+
+! A NON_LVALUE_EXPR is generated for a double negation that simplifies to a 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 simplifies to a 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" } }