Add stack simulator for compilation

1 files changed, 118 insertions, 0 deletions

diff --git a/snug-clean/src/Snug/Compile/Simulate.icl b/snug-clean/src/Snug/Compile/Simulate.icl
new file mode 100644
index 0000000..d1d65ac
--- /dev/null
+++ b/snug-clean/src/Snug/Compile/Simulate.icl
@@ -0,0 +1,118 @@
+implementation module Snug.Compile.Simulate
+
+import StdEnv
+
+import Control.Monad
+import Control.Monad.Identity
+import Control.Monad.State
+import Data.Functor
+
+import MIPS.MIPS32
+import Snug.Compile.ABI
+import Snug.Syntax
+
+:: SimulationState =
+	{ instrs    :: ![[Instruction]]
+	, hp_offset :: !Int
+	, stack     :: ![StackValue]
+	}
+
+:: StackValue
+	= SVImmediate !Immediate
+	| SVRegOffset !Register !Offset /* value is reg + offset */
+
+simulate :: !(Simulator a) -> [Instruction]
+simulate sim = flatten (reverse (execState sim initial).instrs)
+where
+	// TODO: when finishing:
+	// - check that the stack is empty
+	// - update heap pointer
+	initial =
+		{ instrs = []
+		, hp_offset = 0
+		, stack = []
+		}
+
+add :: ![Instruction] -> Simulator ()
+add is = modify \s -> {s & instrs=[is:s.instrs]}
+
+push :: StackValue -> Simulator ()
+push sv = modify \s -> {s & stack=[sv:s.stack]}
+
+pop :: Simulator StackValue
+pop =
+	getState >>= \{stack} ->
+	modify (\s -> {s & stack=tl stack}) $> hd stack
+
+write_heap :: !StackValue -> Simulator StackValue
+write_heap sv =
+	getState >>= \{hp_offset} ->
+	storeStackValue sv hp_offset HeapPtr >>|
+	modify (\s -> {s & hp_offset=hp_offset+4}) $>
+	SVRegOffset HeapPtr hp_offset
+
+storeStackValue :: !StackValue !Offset !Register -> Simulator ()
+storeStackValue (SVImmediate (Immediate i)) doffset dreg
+	| i == 0 = add
+		[ StoreWord R0 doffset dreg
+		]
+	| 0 <= i && i < 0x10000 = add
+		[ OrImmediate TempImm R0 (Immediate i)
+		, StoreWord TempImm doffset dreg
+		]
+	| 0 > i && i >= -0x8000 = add
+		[ AddImmediate Signed TempImm R0 (Immediate i)
+		, StoreWord TempImm doffset dreg
+		]
+	| otherwise = add
+		[ LoadUpperImmediate TempImm (Immediate (i >> 16))
+		, OrImmediate TempImm TempImm (Immediate (i bitand 0xffff))
+		, StoreWord TempImm doffset dreg
+		]
+storeStackValue (SVImmediate imm=:(Address _ _)) doffset dreg = add
+	[ LoadAddress TempImm imm
+	, StoreWord TempImm doffset dreg
+	]
+storeStackValue (SVRegOffset reg 0) doffset dreg = add
+	[ StoreWord reg doffset dreg
+	]
+storeStackValue (SVRegOffset reg offset) doffset dreg = add
+	[ AddImmediate Signed TempImm reg (Immediate offset)
+	, StoreWord TempImm doffset dreg
+	]
+
+buildCons :: !Label !Int -> Simulator ()
+buildCons cons nargs =
+	write_heap (SVImmediate (Address 2 cons)) >>= \addr ->
+	mapM_ (\_ -> pop >>= write_heap) [1..nargs] >>|
+	push addr
+
+pushBasicValue :: !BasicValue -> Simulator ()
+pushBasicValue val = push (SVImmediate (Immediate imm))
+where
+	imm = case val of
+		BVInt i -> i
+		BVChar c -> toInt c
+
+indirectAndEval :: Simulator ()
+indirectAndEval =
+	pop >>= \sv ->
+	case sv of
+		SVRegOffset HeapPtr offset ->
+			add
+				// Build indirection
+				[ LoadAddress TempImm (Address 0 (functionLabel "" NodeEntry "indir"))
+				, StoreWord TempImm 0 FrontEvalPtr
+				] >>|
+			storeStackValue sv 4 FrontEvalPtr >>|
+			add
+				// Evaluate
+				[ AddImmediate Signed FrontEvalPtr HeapPtr (Immediate offset)
+				, Jump NoLink (Direct (Address 0 "eval"))
+				] >>|
+			getState >>= \{hp_offset} ->
+			add
+				[ AddImmediate Signed HeapPtr HeapPtr (Immediate hp_offset)
+				]
+		_ ->
+			abort "unexpected top of stack in indirect\n"