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Now the compiler removes code that has no observable effect.

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This commit is contained in:
acqn 2021-02-22 13:47:32 +08:00 committed by mrdudz
parent 4cb5063e9c
commit a4ad212316
2 changed files with 28 additions and 17 deletions
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22
src/cc65/expr.c
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@ -4188,19 +4188,25 @@ void hie0 (ExprDesc *Expr)
/* Append deferred inc/dec at sequence point */
DoDeferred (SQP_KEEP_NONE, Expr);
/* If the expression didn't generate code or isn't cast to type void,
** emit a warning.
/* If the expression has no observable effect and isn't cast to type
** void, emit a warning and remove useless code if any.
*/
GetCodePos (&End);
if (!ED_MayHaveNoEffect (Expr) &&
(CodeRangeIsEmpty (&Start, &End) ||
(Expr->Flags & E_SIDE_EFFECTS) == 0) &&
IS_Get (&WarnNoEffect) &&
PrevErrorCount == ErrorCount) {
Warning ("Left-hand operand of comma expression has no effect");
if (CodeRangeIsEmpty (&Start, &End) ||
(Expr->Flags & E_SIDE_EFFECTS) == 0) {
if (!ED_MayHaveNoEffect (Expr) &&
IS_Get (&WarnNoEffect) &&
PrevErrorCount == ErrorCount) {
Warning ("Left-hand operand of comma expression has no effect");
}
/* Remove code with no effect */
RemoveCode (&Start);
}
PrevErrorCount = ErrorCount;
/* Remember the current code position */
GetCodePos (&Start);

23
src/cc65/stmt.c
View File

@ -609,18 +609,23 @@ static void Statement (int* PendingToken)
Expr.Flags |= E_NEED_NONE;
Expression0 (&Expr);
/* If the statement didn't generate code, and is not of type
** void, emit a warning.
/* If the statement has no observable effect and isn't cast to type
** void, emit a warning and remove useless code if any.
*/
GetCodePos (&End);
if (!ED_YetToLoad (&Expr) &&
!ED_MayHaveNoEffect (&Expr) &&
(CodeRangeIsEmpty (&Start, &End) ||
(Expr.Flags & E_SIDE_EFFECTS) == 0) &&
IS_Get (&WarnNoEffect) &&
PrevErrorCount == ErrorCount) {
Warning ("Statement has no effect");
if (CodeRangeIsEmpty (&Start, &End) ||
(Expr.Flags & E_SIDE_EFFECTS) == 0) {
if (!ED_MayHaveNoEffect (&Expr) &&
IS_Get (&WarnNoEffect) &&
PrevErrorCount == ErrorCount) {
Warning ("Statement has no effect");
}
/* Remove code with no effect */
RemoveCode (&Start);
}
CheckSemi (PendingToken);
}