Added control flow statement if-then-else

Author: vijayphoenix

src/CodeGen.hs

@@ -28,9 +28,14 @@ module CodeGen (
   alloca,
   execCodegen,
   setBlock,
+  getBlock,
   emptyBlock,
   unikName,
-  entryBlockName
+  entryBlockName,
+  br,
+  phi,
+  cbr,
+  fcmp
 
 )where 
 
@@ -47,6 +52,7 @@ import qualified LLVM.AST as ASTL
 import qualified LLVM.AST.Constant as C
 import qualified LLVM.AST.Float as F
 import qualified LLVM.AST.FloatingPointPredicate as FP
+import qualified LLVM.AST.IntegerPredicate as IP
 
 import Data.Word
 import Data.String
@@ -199,7 +205,8 @@ setBlock bname = do
   modify $ \s -> s { currentBlock = bname }
   return bname
 
-
+getBlock :: Codegen ASTL.Name
+getBlock = gets currentBlock
 
 -- | Alloca Returns an instruction of declaration of 
 -- | A var of allocatedType :: Type , numElements , alignment , metadata 
@@ -288,4 +295,17 @@ store :: ASTL.Operand -> ASTL.Operand -> Codegen ASTL.Operand
 store ptr val = instr $ Store False ptr val Nothing 0 []
 
 load :: ASTL.Operand -> Codegen ASTL.Operand
-load ptr = instr $ Load False ptr Nothing 0 []
+load ptr = instr $ Load False ptr Nothing 0 []
+
+-- Control Flow
+br :: ASTL.Name -> Codegen (ASTL.Named ASTL.Terminator)
+br val = terminator $ ASTL.Do $ ASTL.Br val []
+
+cbr :: ASTL.Operand -> ASTL.Name -> ASTL.Name -> Codegen (ASTL.Named ASTL.Terminator)
+cbr cond tr fl = terminator $ ASTL.Do $ ASTL.CondBr cond tr fl []
+
+phi :: ASTL.Type -> [(ASTL.Operand, ASTL.Name)] -> Codegen ASTL.Operand
+phi ty incoming = instr $ ASTL.Phi ty incoming []
+
+fcmp :: IP.IntegerPredicate -> ASTL.Operand -> ASTL.Operand -> Codegen ASTL.Operand
+fcmp cond a b = instr $ ICmp cond a b []

src/Emit.hs

@@ -41,7 +41,7 @@ import qualified LLVM.AST.Float as F
 import qualified LLVM.AST.FloatingPointPredicate as FP
 import qualified LLVM.AST.CallingConvention as CC
 import qualified LLVM.AST.Attribute as A
-
+import qualified LLVM.AST.IntegerPredicate as IP
 
 import Control.Monad.State
 import Control.Applicative
@@ -172,6 +172,7 @@ exprGen (FuncCallStmt f) = funcCallGen f
 exprGen (LiteralStmt st) = literalGen st
 exprGen (BinOpCallStmt st) = binOpCallGen st
 exprGen (DeclarationStmt st) = declarationGen st
+exprGen (IfthenStmt st) = ifthenGen st
 
 binOpCallGen :: ASTp.BinOpCall -> Codegen ASTL.Operand
 binOpCallGen (BinOpCall op lhs rhs) = do 
@@ -223,3 +224,34 @@ exprListGen (a:[]) = exprGen a
 exprListGen (x:xs) = do
   exprGen x
   exprListGen xs
+
+ifthenGen :: ASTp.Ifthen -> Codegen ASTL.Operand
+ifthenGen (ASTp.Ifthen cond tr fl) = do
+  ifthen <- addBlock "if.then"
+  ifelse <- addBlock "if.else"
+  ifexit <- addBlock "if.exit"
+  cond <- exprGen cond
+  test <- fcmp IP.NE zero cond
+  cbr test ifthen ifelse      -- Branch based on the condition
+
+  setBlock ifthen
+  trval <- exprGen tr         -- Generate code for the true branch
+  br ifexit                   -- Branch to the merge block
+  ifthen <- getBlock
+
+  setBlock ifelse
+  flval <- exprGen fl         -- Generate code for the false branch
+  br ifexit                   -- Branch to the merge block
+  ifelse <- getBlock
+
+  setBlock ifexit
+  phi intL [(trval, ifthen), (flval, ifelse)]
+
+cons :: C.Constant -> Operand
+cons = ConstantOperand
+
+one = cons $ C.Int 32 1
+zero = cons $ C.Int 32 0
+
+ -- def fib(int x):int { if(x) then {fib(x-1)+fib(x-2)} else {1};}
+  -- def fac(int x):int{ if(x) then { fac(x-1)*x} else {1};}

src/Parser.hs

@@ -1,6 +1,7 @@
 module Parser (
     moduleParser,
-    funcParser
+    funcParser,
+    ifthenParser
 )where 
 
 import Lexer 
@@ -46,6 +47,7 @@ funcParser = do
 
 exprParser :: Parser Expr
 exprParser = try primary
+           <|> ifthenStmtParser
            <|> declarationStmtParser
 
 variableParser :: Parser Expr
@@ -273,6 +275,10 @@ varDeclParser = do
     names <- vListParser
     return $ VarDecl t names
 
+ifthenStmtParser :: Parser Expr 
+ifthenStmtParser = do
+    res <- ifthenParser
+    return $ IfthenStmt res
 
 ifthenParser :: Parser Ifthen
 ifthenParser = do