From 69d5d648a9630a85a0ba9dbe0f79345152294112 Mon Sep 17 00:00:00 2001
From: florian <florian@freepascal.org>
Date: Tue, 21 Sep 2021 23:09:33 +0200
Subject: [PATCH]   + more unary minus optimizations   * test extended

---
 compiler/nmat.pas   | 17 +++++++++++++++++
 tests/tbs/tb0685.pp | 14 ++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/compiler/nmat.pas b/compiler/nmat.pas
index ade96bbbf6..a9f8b1f790 100644
--- a/compiler/nmat.pas
+++ b/compiler/nmat.pas
@@ -972,6 +972,23 @@ implementation
                 exit;
               end;
 
+            {
+              -(-left*right) or -(left*-right) => right*left
+
+              this operation is always valid as reals do not use a two's complement representation for negative
+              numbers, -real means just flip the sign bit
+            }
+            if (left.nodetype=muln) and ((taddnode(left).left.nodetype=unaryminusn)) then
+              begin
+                result:=caddnode.create(muln,taddnode(left).right.getcopy,tunaryminusnode(taddnode(left).left).left.getcopy);
+                exit;
+              end;
+            if (left.nodetype=muln) and ((taddnode(left).right.nodetype=unaryminusn)) then
+              begin
+                result:=caddnode.create(muln,taddnode(left).left.getcopy,tunaryminusnode(taddnode(left).right).left.getcopy);
+                exit;
+              end;
+
             { --node => node
               this operation is always valid as reals do not use a two's complement representation for negative
               numbers, -real means just flip the sign bit
diff --git a/tests/tbs/tb0685.pp b/tests/tbs/tb0685.pp
index 1970538db0..881adb93d3 100644
--- a/tests/tbs/tb0685.pp
+++ b/tests/tbs/tb0685.pp
@@ -44,5 +44,19 @@ begin
   if (d3<>0.0) or not(TDoubleRec(d3).Sign) then
     halt(7);
 
+  d1:=1.0;
+  d2:=2.0;
+  d3:=-(d2*-d1);
+  writeln(d3);
+  if (d3<>2.0) or (TDoubleRec(d3).Sign) then
+    halt(8);
+
+  d1:=1.0;
+  d2:=2.0;
+  d3:=-(-d2*d1);
+  writeln(d3);
+  if (d3<>2.0) or (TDoubleRec(d3).Sign) then
+    halt(9);
+
   writeln('ok');
 end.