From 59c77a48b5d4533ab71b5baddfa203186f39b0c2 Mon Sep 17 00:00:00 2001
From: florian <florian@freepascal.org>
Date: Tue, 5 Mar 2024 22:10:56 +0100
Subject: [PATCH]   * transform -x-1 into not(x), resolves #40313

---
 compiler/nadd.pas   | 7 +++++++
 tests/tbs/tb0711.pp | 9 +++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 tests/tbs/tb0711.pp

diff --git a/compiler/nadd.pas b/compiler/nadd.pas
index 354868501c..1034c58083 100644
--- a/compiler/nadd.pas
+++ b/compiler/nadd.pas
@@ -932,6 +932,13 @@ implementation
                 left:=nil;
                 tmoddivnode(right).right:=nil;
                 exit;
+              end
+
+            { transform -x-1 into not(x) }
+            else if is_signed(ld) and is_constintnode(right) and (tordconstnode(right).value=1) and (left.nodetype=unaryminusn) then
+              begin
+                result:=cnotnode.create(tunaryminusnode(left).left.getcopy);
+                exit;
               end;
           end;
 
diff --git a/tests/tbs/tb0711.pp b/tests/tbs/tb0711.pp
new file mode 100644
index 0000000000..f9d8173bfa
--- /dev/null
+++ b/tests/tbs/tb0711.pp
@@ -0,0 +1,9 @@
+var
+  l : longint;
+
+begin
+  l:=1234;
+
+  if -l-1<>-1235 then
+    halt(1);
+end.
\ No newline at end of file