From 8078675aae7bab023f875310ff92b59a744a5706 Mon Sep 17 00:00:00 2001
From: Stephen Heumann <stephenheumann@gmail.com>
Date: Thu, 11 Feb 2021 14:50:36 -0600
Subject: [PATCH] Do not eliminate expressions with side effects in "exp | -1"
 or "exp & 0".

This was previously happening in intermediate code peephole optimization.

The following example program demonstrates the problem:

#pragma optimize 1
int main(void) {
        int i = 0;
        long j = 0;
        ++i | -1;
        ++i & 0;
        ++j | -1;
        ++j & 0;
        return i+j; /* should be 4 */
}
---
 DAG.pas | 24 ++++++++++++++++--------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/DAG.pas b/DAG.pas
index a6a3be5..51f8a88 100644
--- a/DAG.pas
+++ b/DAG.pas
@@ -896,8 +896,10 @@ case op^.opcode of			{check for optimizations of this node}
          opv := op^.left;
          end {if}
       else if op^.right^.opcode = pc_ldc then begin
-         if op^.right^.lval = 0 then
-            opv := op^.right
+         if op^.right^.lval = 0 then begin
+            if not SideEffects(op^.left) then
+               opv := op^.right;
+            end {if}
          else if op^.right^.lval = -1 then
             opv := op^.left;
          end; {else if}
@@ -911,8 +913,10 @@ case op^.opcode of			{check for optimizations of this node}
          opv := op^.left;
          end {if}
       else if op^.right^.opcode = pc_ldc then begin
-         if op^.right^.lval = -1 then
-            opv := op^.right
+         if op^.right^.lval = -1 then begin
+            if not SideEffects(op^.left) then
+               opv := op^.right;
+            end {if}
          else if op^.right^.lval = 0 then
             opv := op^.left;
          end; {else if}
@@ -943,8 +947,10 @@ case op^.opcode of			{check for optimizations of this node}
          opv := op^.left;
          end {if}
       else if op^.right^.opcode = pc_ldc then begin
-         if op^.right^.q = 0 then
-            opv := op^.right
+         if op^.right^.q = 0 then begin
+            if not SideEffects(op^.left) then
+               opv := op^.right;
+            end {if}
          else if op^.right^.q = -1 then
             opv := op^.left;
          end; {else if}
@@ -981,8 +987,10 @@ case op^.opcode of			{check for optimizations of this node}
          opv := op^.left;
          end {if}
       else if op^.right^.opcode = pc_ldc then begin
-         if op^.right^.q = -1 then
-            opv := op^.right
+         if op^.right^.q = -1 then begin
+            if not SideEffects(op^.left) then
+               opv := op^.right;
+            end {if}
          else if op^.right^.q = 0 then
             opv := op^.left;
          end; {else if}