From 0f437dcf0eda470c3eaf068f3fd51356083e70ed Mon Sep 17 00:00:00 2001
From: Neil Brown <neil@twistedsquare.com>
Date: Tue, 26 Feb 2008 17:20:29 +0000
Subject: [PATCH] Fixed the behaviour of the right-shift operator to match how
 it should work in occam

---
 backends/GenerateC.hs | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/backends/GenerateC.hs b/backends/GenerateC.hs
index a6b68f3..b94c9df 100644
--- a/backends/GenerateC.hs
+++ b/backends/GenerateC.hs
@@ -263,6 +263,15 @@ cgetScalarType A.Timer = Just "Time"
 cgetScalarType A.Time = Just "Time"
 cgetScalarType _ = Nothing
 
+cgetUnsignedType :: A.Type -> Maybe String
+cgetUnsignedType t | elem t [A.Byte, A.UInt16, A.UInt32, A.UInt64] = cgetScalarType t
+cgetUnsignedType A.Int8 = cgetScalarType A.Byte
+cgetUnsignedType A.Int = cgetScalarType A.UInt32
+cgetUnsignedType A.Int16 = cgetScalarType A.UInt16
+cgetUnsignedType A.Int32 = cgetScalarType A.UInt32
+cgetUnsignedType A.Int64 = cgetScalarType A.UInt64
+cgetUnsignedType _ = Nothing
+
 -- | Generate the C type corresponding to a variable being declared.
 -- It must be possible to use this in arrays.
 cgenType :: A.Type -> CGen ()
@@ -827,7 +836,18 @@ cgenDyadic _ A.Plus e f = call genSimpleDyadic "+" e f
 cgenDyadic _ A.Minus e f = call genSimpleDyadic "-" e f
 cgenDyadic _ A.Times e f = call genSimpleDyadic "*" e f
 cgenDyadic _ A.LeftShift e f = call genSimpleDyadic "<<" e f
-cgenDyadic _ A.RightShift e f = call genSimpleDyadic ">>" e f
+cgenDyadic m A.RightShift e f
+  = do t <- typeOfExpression e
+       (normalT, unsignedT) <- case (cgetScalarType t, cgetUnsignedType t) of
+         (Just x, Just y) -> return (x,y)
+         _ -> diePC m $ formatCode "Attempting to shift non-integer type: %" t
+       if (normalT == unsignedT)
+         then call genSimpleDyadic ">>" e f
+         else do tell ["((", normalT, ")(((", unsignedT, ")"]
+                 call genExpression e
+                 tell [") >> "]
+                 call genExpression f
+                 tell ["))"]
 cgenDyadic _ A.BitAnd e f = call genSimpleDyadic "&" e f
 cgenDyadic _ A.BitOr e f = call genSimpleDyadic "|" e f
 cgenDyadic _ A.BitXor e f = call genSimpleDyadic "^" e f