From f2d15b8fc757e55b40cbd5a5ff7dbbfa878e2bf1 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Mon, 26 Mar 2018 19:57:18 -0500
Subject: [PATCH] Fix optimizer bug where casts with unused results could
 sometimes cause stack corruption.

This problem could lead to crashes in code like the following (derived from a csmith-generated test case):

#pragma optimize 1
static int main(void) {
    long i = 2;
    (long)(i > 1);
}
---
 DAG.pas | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/DAG.pas b/DAG.pas
index 39a6984..daced54 100644
--- a/DAG.pas
+++ b/DAG.pas
@@ -1840,8 +1840,11 @@ case op^.opcode of			{check for optimizations of this node}
       end; {case pc_not}
 
    pc_pop: begin			{pc_pop}
-      if op^.left^.opcode = pc_cnv then
+      if op^.left^.opcode = pc_cnv then begin
+         fromtype.i := (op^.left^.q & $00F0) >> 4;
+         op^.optype := fromtype.optype;
          op^.left := op^.left^.left;
+         end; {if}
       opcode := op^.left^.opcode;
       if opcode = pc_cop then begin
          op^.left^.opcode := pc_str;