From 66f1f829431bb6b8b6da47d6bb86c66d9c35b240 Mon Sep 17 00:00:00 2001
From: uz <uz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Fri, 20 Jan 2012 15:54:43 +0000
Subject: [PATCH] Masking a bit field is unnecessary if there was no shift
 operation or if the shift operation shifted just zeroes into the value.

git-svn-id: svn://svn.cc65.org/cc65/trunk@5412 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 src/cc65/loadexpr.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/cc65/loadexpr.c b/src/cc65/loadexpr.c
index 4802dbb2b..99c5684d1 100644
--- a/src/cc65/loadexpr.c
+++ b/src/cc65/loadexpr.c
@@ -162,8 +162,11 @@ void LoadExpr (unsigned Flags, struct ExprDesc* Expr)
             unsigned F = CF_INT | CF_UNSIGNED | CF_CONST | (Flags & CF_TEST);
             /* Shift right by the bit offset */
             g_asr (F, Expr->BitOffs);
-            /* And by the width */
-            g_and (F, (0x0001U << Expr->BitWidth) - 1U);
+            /* And by the width if the field doesn't end on an int boundary */
+            if (Expr->BitOffs + Expr->BitWidth != CHAR_BITS &&
+                Expr->BitOffs + Expr->BitWidth != INT_BITS) {
+                g_and (F, (0x0001U << Expr->BitWidth) - 1U);
+            }
         }
 
         /* Expression was tested */