void SwitchStatement (void)
/* Handle a switch statement for chars with a cmp cascade for the selector */
{
ExprDesc SwitchExpr; /* Switch statement expression */
CodeMark CaseCodeStart; /* Start of code marker */
CodeMark SwitchCodeStart;/* Start of switch code */
CodeMark SwitchCodeEnd; /* End of switch code */
unsigned ExitLabel; /* Exit label */
unsigned SwitchCodeLabel;/* Label for the switch code */
int HaveBreak = 0; /* True if the last statement had a break */
int RCurlyBrace; /* True if last token is right curly brace */
SwitchCtrl* OldSwitch; /* Pointer to old switch control data */
SwitchCtrl SwitchData; /* New switch data */
/* Eat the "switch" token */
NextToken ();
/* Read the switch expression and load it into the primary. It must have
* integer type.
*/
ConsumeLParen ();
Expression0 (&SwitchExpr);
if (!IsClassInt (SwitchExpr.Type)) {
Error ("Switch quantity is not an integer");
/* To avoid any compiler errors, make the expression a valid int */
ED_MakeConstAbsInt (&SwitchExpr, 1);
}
ConsumeRParen ();
/* Add a jump to the switch code. This jump is usually unnecessary,
* because the switch code will moved up just behind the switch
* expression. However, in rare cases, there's a label at the end of
* the switch expression. This label will not get moved, so the code
* jumps around the switch code, and after moving the switch code,
* things look really weird. If we add a jump here, we will never have
* a label attached to the current code position, and the jump itself
* will get removed by the optimizer if it is unnecessary.
*/
SwitchCodeLabel = GetLocalLabel ();
g_jump (SwitchCodeLabel);
/* Remember the current code position. We will move the switch code
* to this position later.
*/
GetCodePos (&CaseCodeStart);
/* Setup the control structure, save the old and activate the new one */
SwitchData.Nodes = NewCollection ();
SwitchData.ExprType = UnqualifiedType (SwitchExpr.Type[0].C);
SwitchData.Depth = SizeOf (SwitchExpr.Type);
SwitchData.DefaultLabel = 0;
OldSwitch = Switch;
Switch = &SwitchData;
/* Get the exit label for the switch statement */
ExitLabel = GetLocalLabel ();
/* Create a loop so we may use break. */
AddLoop (ExitLabel, 0);
/* Make sure a curly brace follows */
if (CurTok.Tok != TOK_LCURLY) {
Error ("`{' expected");
}
/* Parse the following statement, which will actually be a compound
* statement because of the curly brace at the current input position
*/
HaveBreak = Statement (&RCurlyBrace);
/* Check if we had any labels */
if (CollCount (SwitchData.Nodes) == 0 && SwitchData.DefaultLabel == 0) {
Warning ("No case labels");
}
/* If the last statement did not have a break, we may have an open
* label (maybe from an if or similar). Emitting code and then moving
* this code to the top will also move the label to the top which is
* wrong. So if the last statement did not have a break (which would
* carry the label), add a jump to the exit. If it is useless, the
* optimizer will remove it later.
*/
if (!HaveBreak) {
g_jump (ExitLabel);
}
/* Remember the current position */
GetCodePos (&SwitchCodeStart);
/* Output the switch code label */
g_defcodelabel (SwitchCodeLabel);
/* Generate code */
if (SwitchData.DefaultLabel == 0) {
/* No default label, use switch exit */
SwitchData.DefaultLabel = ExitLabel;
}
g_switch (SwitchData.Nodes, SwitchData.DefaultLabel, SwitchData.Depth);
/* Move the code to the front */
GetCodePos (&SwitchCodeEnd);
MoveCode (&SwitchCodeStart, &SwitchCodeEnd, &CaseCodeStart);
/* Define the exit label */
g_defcodelabel (ExitLabel);
/* Exit the loop */
DelLoop ();
/* Switch back to the enclosing switch statement if any */
Switch = OldSwitch;
/* Free the case value tree */
FreeCaseNodeColl (SwitchData.Nodes);
/* If the case statement was (correctly) terminated by a closing curly
* brace, skip it now.
*/
if (RCurlyBrace) {
NextToken ();
}
}
static void ForStatement (void)
/* Handle a 'for' statement */
{
ExprDesc lval1;
ExprDesc lval3;
int HaveIncExpr;
CodeMark IncExprStart;
CodeMark IncExprEnd;
int PendingToken;
/* Get several local labels needed later */
unsigned TestLabel = GetLocalLabel ();
unsigned BreakLabel = GetLocalLabel ();
unsigned IncLabel = GetLocalLabel ();
unsigned BodyLabel = GetLocalLabel ();
/* Skip the FOR token */
NextToken ();
/* Add the loop to the loop stack. A continue jumps to the start of the
** the increment condition.
*/
AddLoop (BreakLabel, IncLabel);
/* Skip the opening paren */
ConsumeLParen ();
/* Parse the initializer expression */
if (CurTok.Tok != TOK_SEMI) {
Expression0 (&lval1);
}
ConsumeSemi ();
/* Label for the test expressions */
g_defcodelabel (TestLabel);
/* Parse the test expression */
if (CurTok.Tok != TOK_SEMI) {
Test (BodyLabel, 1);
g_jump (BreakLabel);
} else {
g_jump (BodyLabel);
}
ConsumeSemi ();
/* Remember the start of the increment expression */
GetCodePos (&IncExprStart);
/* Label for the increment expression */
g_defcodelabel (IncLabel);
/* Parse the increment expression */
HaveIncExpr = (CurTok.Tok != TOK_RPAREN);
if (HaveIncExpr) {
Expression0 (&lval3);
}
/* Jump to the test */
g_jump (TestLabel);
/* Remember the end of the increment expression */
GetCodePos (&IncExprEnd);
/* Skip the closing paren */
ConsumeRParen ();
/* Loop body */
g_defcodelabel (BodyLabel);
Statement (&PendingToken);
/* If we had an increment expression, move the code to the bottom of
** the loop. In this case we don't need to jump there at the end of
** the loop body.
*/
if (HaveIncExpr) {
CodeMark Here;
GetCodePos (&Here);
MoveCode (&IncExprStart, &IncExprEnd, &Here);
} else {
/* Jump back to the increment expression */
g_jump (IncLabel);
}
/* Skip a pending token if we have one */
SkipPending (PendingToken);
/* Declare the break label */
g_defcodelabel (BreakLabel);
/* Remove the loop from the loop stack */
DelLoop ();
}