public void CGenDecln(Env env, CGenState state) {
// .text
// [.globl <func>]
// <func>:
// pushl %ebp
// movl %esp, %ebp
//
state.TEXT();
Env.Entry entry = env.Find(this.name).Value;
state.COMMENT(ToString());
switch (entry.Kind) {
case Env.EntryKind.GLOBAL:
switch (this.scs) {
case StorageClass.AUTO:
case StorageClass.EXTERN:
state.GLOBL(this.name);
break;
case StorageClass.STATIC:
// static definition
break;
default:
throw new InvalidOperationException();
}
break;
default:
throw new InvalidOperationException();
}
state.CGenFuncStart(this.name);
state.InFunction(GotoLabelsGrabber.GrabLabels(this.stmt));
this.stmt.CGenStmt(env, state);
state.CGenLabel(state.ReturnLabel);
state.OutFunction();
// leave
// ret
state.LEAVE();
state.RET();
state.NEWLINE();
}
// * function;
// * extern function;
// * static function;
// * obj;
// * obj = Init;
// * static obj;
// * static obj = Init;
// * extern obj;
// * extern obj = Init;
public void CGenDecln(Env env, CGenState state) {
if (env.IsGlobal()) {
if (this.initr.IsSome) {
Initr initr = this.initr.Value;
switch (this.scs) {
case StorageClass.AUTO:
state.GLOBL(this.name);
break;
case StorageClass.EXTERN:
throw new InvalidProgramException();
case StorageClass.STATIC:
break;
case StorageClass.TYPEDEF:
// Ignore.
return;
default:
throw new InvalidProgramException();
}
state.DATA();
state.ALIGN(ExprType.ALIGN_LONG);
state.CGenLabel(this.name);
Int32 last = 0;
initr.Iterate(this.type, (Int32 offset, Expr expr) => {
if (offset > last) {
state.ZERO(offset - last);
}
if (!expr.IsConstExpr) {
throw new InvalidOperationException("Cannot initialize with non-const expression.");
}
switch (expr.Type.Kind) {
// TODO: without const char/short, how do I initialize?
case ExprTypeKind.CHAR:
case ExprTypeKind.UCHAR:
case ExprTypeKind.SHORT:
case ExprTypeKind.USHORT:
throw new NotImplementedException();
case ExprTypeKind.LONG:
state.LONG(((ConstLong)expr).Value);
break;
case ExprTypeKind.ULONG:
state.LONG((Int32)((ConstULong)expr).Value);
break;
case ExprTypeKind.POINTER:
state.LONG((Int32)((ConstPtr)expr).Value);
break;
case ExprTypeKind.FLOAT:
byte[] float_bytes = BitConverter.GetBytes(((ConstFloat)expr).Value);
Int32 intval = BitConverter.ToInt32(float_bytes, 0);
state.LONG(intval);
break;
case ExprTypeKind.DOUBLE:
byte[] double_bytes = BitConverter.GetBytes(((ConstDouble)expr).Value);
Int32 first_int = BitConverter.ToInt32(double_bytes, 0);
Int32 second_int = BitConverter.ToInt32(double_bytes, 4);
state.LONG(first_int);
state.LONG(second_int);
break;
default:
throw new InvalidProgramException();
}
last = offset + expr.Type.SizeOf;
});
} else {
// Global without initialization.
switch (this.scs) {
case StorageClass.AUTO:
// .comm name,size,align
break;
case StorageClass.EXTERN:
break;
case StorageClass.STATIC:
// .local name
// .comm name,size,align
state.LOCAL(this.name);
break;
case StorageClass.TYPEDEF:
// Ignore.
return;
default:
throw new InvalidProgramException();
}
if (this.type.Kind != ExprTypeKind.FUNCTION) {
state.COMM(this.name, this.type.SizeOf, ExprType.ALIGN_LONG);
}
}
state.NEWLINE();
} else {
// stack object
state.CGenExpandStackTo(env.StackSize, ToString());
Int32 stack_size = env.StackSize;
// pos should be equal to stack_size, but whatever...
Int32 pos = env.Find(this.name).Value.Offset;
if (this.initr.IsNone) {
return;
}
Initr initr = this.initr.Value;
initr.Iterate(this.type, (Int32 offset, Expr expr) => {
Reg ret = expr.CGenValue(state);
switch (expr.Type.Kind) {
case ExprTypeKind.CHAR:
case ExprTypeKind.UCHAR:
state.MOVB(Reg.EAX, pos + offset, Reg.EBP);
break;
case ExprTypeKind.SHORT:
case ExprTypeKind.USHORT:
state.MOVW(Reg.EAX, pos + offset, Reg.EBP);
break;
case ExprTypeKind.DOUBLE:
state.FSTPL(pos + offset, Reg.EBP);
break;
case ExprTypeKind.FLOAT:
state.FSTPS(pos + offset, Reg.EBP);
break;
case ExprTypeKind.LONG:
case ExprTypeKind.ULONG:
case ExprTypeKind.POINTER:
state.MOVL(Reg.EAX, pos + offset, Reg.EBP);
break;
case ExprTypeKind.STRUCT_OR_UNION:
state.MOVL(Reg.EAX, Reg.ESI);
state.LEA(pos + offset, Reg.EBP, Reg.EDI);
state.MOVL(expr.Type.SizeOf, Reg.ECX);
state.CGenMemCpy();
break;
case ExprTypeKind.ARRAY:
case ExprTypeKind.FUNCTION:
throw new InvalidProgramException($"How could a {expr.Type.Kind} be in a init list?");
default:
throw new InvalidProgramException();
}
state.CGenForceStackSizeTo(stack_size);
});
} // stack object
}
public override Reg CGenValue(CGenState state) {
// GCC's IA-32 calling convention
// Caller is responsible to push all arguments to the stack in reverse order.
// Each argument is at least aligned to 4 bytes - even a char would take 4 bytes.
// The return Value is stored in %eax, or %st(0), if it is a scalar.
//
// The stack would look like this after pushing all the arguments:
// +--------+
// | .... |
// +--------+
// | argn |
// +--------+
// | .... |
// +--------+
// | arg2 |
// +--------+
// | arg1 |
// +--------+ <- %esp before call
//
// Things are different with structs and unions.
// Since structs may not fit in 4 bytes, it has to be returned in memory.
// Caller allocates a chunk of memory for the struct and push the address of it as an extra argument.
// Callee returns %eax with that address.
//
// The stack would look like this after pushing all the arguments:
// +--------+
// +--> | struct | <- struct should be returned here.
// | +--------+
// | | argn |
// | +--------+
// | | .... |
// | +--------+
// | | arg2 |
// | +--------+
// | | arg1 |
// | +--------+
// +----| addr | <- %esp before call
// +--------+
//
state.NEWLINE();
state.COMMENT($"Before pushing the arguments, stack size = {state.StackSize}.");
var r_pack = Utils.PackArguments(this.Args.Select(_ => _.Type).ToList());
Int32 pack_size = r_pack.Item1;
IReadOnlyList<Int32> offsets = r_pack.Item2;
if (this.Type is StructOrUnionType) {
// If the function returns a struct
// Allocate space for return Value.
state.COMMENT("Allocate space for returning stack.");
state.CGenExpandStackWithAlignment(this.Type.SizeOf, this.Type.Alignment);
// Temporarily store the address in %eax.
state.MOVL(Reg.ESP, Reg.EAX);
// add an extra argument and move all other arguments upwards.
pack_size += ExprType.SIZEOF_POINTER;
offsets = offsets.Select(_ => _ + ExprType.SIZEOF_POINTER).ToList();
}
// Allocate space for arguments.
// If returning struct, the extra pointer is included.
state.COMMENT($"Arguments take {pack_size} bytes.");
state.CGenExpandStackBy(pack_size);
state.NEWLINE();
// Store the address as the first argument.
if (this.Type is StructOrUnionType) {
state.COMMENT("Putting extra argument for struct return address.");
state.MOVL(Reg.EAX, 0, Reg.ESP);
state.NEWLINE();
}
// This is the stack size before calling the function.
Int32 header_base = -state.StackSize;
// Push the arguments onto the stack in reverse order
for (Int32 i = this.Args.Count; i-- > 0;) {
Expr arg = this.Args[i];
Int32 pos = header_base + offsets[i];
state.COMMENT($"Argument {i} is at {pos}");
Reg ret = arg.CGenValue(state);
switch (arg.Type.Kind) {
case ExprTypeKind.ARRAY:
case ExprTypeKind.CHAR:
case ExprTypeKind.UCHAR:
case ExprTypeKind.SHORT:
case ExprTypeKind.USHORT:
case ExprTypeKind.LONG:
case ExprTypeKind.ULONG:
case ExprTypeKind.POINTER:
if (ret != Reg.EAX) {
throw new InvalidProgramException();
}
state.MOVL(Reg.EAX, pos, Reg.EBP);
break;
case ExprTypeKind.DOUBLE:
if (ret != Reg.ST0) {
throw new InvalidProgramException();
}
state.FSTPL(pos, Reg.EBP);
break;
case ExprTypeKind.FLOAT:
if (ret != Reg.ST0) {
throw new InvalidProgramException();
}
state.FSTPL(pos, Reg.EBP);
break;
case ExprTypeKind.STRUCT_OR_UNION:
if (ret != Reg.EAX) {
throw new InvalidProgramException();
}
state.MOVL(Reg.EAX, Reg.ESI);
state.LEA(pos, Reg.EBP, Reg.EDI);
state.MOVL(arg.Type.SizeOf, Reg.ECX);
state.CGenMemCpy();
break;
default:
throw new InvalidProgramException();
}
state.NEWLINE();
}
// When evaluating arguments, the stack might be changed.
// We must restore the stack.
state.CGenForceStackSizeTo(-header_base);
// Get function address
if (this.Func.Type is FunctionType) {
this.Func.CGenAddress(state);
} else if (this.Func.Type is PointerType) {
this.Func.CGenValue(state);
} else {
throw new InvalidProgramException();
}
state.CALL("*%eax");
state.COMMENT("Function returned.");
state.NEWLINE();
if (this.Type.Kind == ExprTypeKind.FLOAT || this.Type.Kind == ExprTypeKind.DOUBLE) {
return Reg.ST0;
}
return Reg.EAX;
}
