From db98f7842d80c4241f273569d4a1c5c0b3de823c Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Mon, 26 Mar 2018 18:20:36 -0500
Subject: [PATCH] Fix mis-evaluation of certain equality comparisons with
 intermediate code optimization.

This affected comparisons of the form "logical operation or comparison == constant other than 0 or 1". These should always evaluate to 0 (false), but could mis-evaluate to true due to the bad optimization.

The following program gives an example showing the problem:

#pragma optimize 1
int main(void) {
        int i = 0, j = 42;
        return (i || j) == 123;
}
---
 DAG.pas | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/DAG.pas b/DAG.pas
index 36cefd7..c5e2121 100644
--- a/DAG.pas
+++ b/DAG.pas
@@ -1329,7 +1329,7 @@ case op^.opcode of			{check for optimizations of this node}
                end; {case}
             end {if}
          else if op^.right^.optype in [cgByte, cgUByte, cgWord, cgUWord] then begin
-            if op^.right^.q <> 0 then
+            if op^.right^.q = 1 then
                if op^.left^.opcode in
          	  [pc_and,pc_ior,pc_neq,pc_equ,pc_geq,pc_leq,pc_les,pc_grt]
                   then begin
@@ -1338,7 +1338,7 @@ case op^.opcode of			{check for optimizations of this node}
                   end; {if}
             end {else if}
          else if op^.right^.optype in [cgLong, cgULong] then begin
-            if op^.right^.lval <> 0 then
+            if op^.right^.lval = 1 then
                if op^.left^.opcode in
          	  [pc_and,pc_ior,pc_neq,pc_equ,pc_geq,pc_leq,pc_les,pc_grt]
                   then begin