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-rw-r--r--c.c132
1 files changed, 112 insertions, 20 deletions
diff --git a/c.c b/c.c
index 7b64b8f..83a4df5 100644
--- a/c.c
+++ b/c.c
@@ -11,7 +11,8 @@ struct comp {
struct arena *fnarena, *exarena;
struct span fnblkspan;
uint loopdepth, switchdepth;
- struct block *loopbreak, *loopcont;
+ struct block *breakto, *loopcont;
+ struct switchstmt *switchstmt;
struct label *labels;
};
@@ -672,7 +673,7 @@ tkprec(int tt)
/* param ident is a kludge to support block labels without backtracking or extra lookahead
* see stmt() */
static struct expr
-exprparse(struct comp *cm, int prec, const struct token *ident)
+exprparse(struct comp *cm, int prec, const struct token *ident, bool fromstmt)
{
struct token tk, tk2;
struct span span;
@@ -710,7 +711,7 @@ Unary:
unops[nunop].t0 = 0;
unops[nunop].tt = tk.t;
if (++nunop >= arraylength(unops)) {
- ex = exprparse(cm, 999, NULL);
+ ex = exprparse(cm, 999, NULL, 0);
break;
}
goto Unary;
@@ -761,7 +762,7 @@ Unary:
unops[nunop].span = tk.span;
unops[nunop].ty = decl.ty;
if (++nunop >= arraylength(unops)) {
- ex = exprparse(cm, 999, NULL);
+ ex = exprparse(cm, 999, NULL, 0);
break;
}
goto Unary;
@@ -783,7 +784,7 @@ Unary:
ex = mkexpr(ENUMLIT, span, mktype(targ_sizetype), .u = typesize(ty));
break;
default:
- fatal(&tk.span, "expected expression (near %'tk)", &tk);
+ fatal(&tk.span, "expected %s (near %'tk)", fromstmt ? "statement" : "expression", &tk);
}
/* postfix operators */
@@ -945,7 +946,7 @@ Postfix:
/* ex OP rhs */
span.sl = tk.span.sl;
span.ex = ex.span.ex;
- rhs = exprparse(cm, opprec + leftassoc, NULL);
+ rhs = exprparse(cm, opprec + leftassoc, NULL, 0);
if (!joinspan(&span.ex, tk.span.ex) || !joinspan(&span.ex, rhs.span.ex))
span.ex = tk.span.ex;
ty = bintypecheck(&span, tk.t, &ex, &rhs);
@@ -982,19 +983,19 @@ Postfix:
static struct expr
expr(struct comp *cm)
{
- return exprparse(cm, bintab['='].prec, NULL); /* non-comma expr */
+ return exprparse(cm, bintab['='].prec, NULL, 0); /* non-comma expr */
}
static struct expr
constantexpr(struct comp *cm)
{
- return exprparse(cm, bintab['?'].prec, NULL); /* conditional-expr */
+ return exprparse(cm, bintab['?'].prec, NULL, 0); /* conditional-expr */
}
static struct expr
commaexpr(struct comp *cm)
{
- return exprparse(cm, 1, NULL);
+ return exprparse(cm, 1, NULL, 0);
}
/****************/
@@ -3114,18 +3115,79 @@ loopbody(struct comp *cm, struct function *fn, struct block *brk, struct block *
struct block *save[2];
bool terminates = 0;
- save[0] = cm->loopbreak, save[1] = cm->loopcont;
- cm->loopbreak = brk, cm->loopcont = cont;
+ save[0] = cm->breakto, save[1] = cm->loopcont;
+ cm->breakto = brk, cm->loopcont = cont;
++cm->loopdepth;
terminates = stmt(cm, fn);
--cm->loopdepth;
- cm->loopbreak = save[0], cm->loopcont = save[1];
+ cm->breakto = save[0], cm->loopcont = save[1];
return terminates;
}
+#define EMITS if (doemit && !nerror)
+
+struct swcase {
+ vlong val;
+ struct block *blk;
+};
+struct switchstmt {
+ struct block *bdefault;
+ vec_of(struct swcase) cases;
+};
+
+static void
+genswitch(struct comp *cm, struct function *fn, const struct expr *ex)
+{
+ union ref sel;
+ bool doemit = fn->curblk;
+ struct block *begin = NULL, *end = NULL, *breaksave = cm->breakto;
+ struct switchstmt *stsave = cm->switchstmt, st = {0};
+ enum irclass k = type2cls[ex->ty.t];
+ struct swcase casebuf[8];
+ vinit(&st.cases, casebuf, arraylength(casebuf));
+
+ end = newblk(fn);
+ EMITS {
+ sel = exprvalue(fn, ex);
+ assert(isint(ex->ty));
+ }
+ cm->switchstmt = &st;
+ cm->breakto = end;
+ begin = fn->curblk;
+ fn->curblk = NULL;
+ stmt(cm, fn);
+ doemit = fn->curblk;
+ cm->switchstmt = stsave;
+ cm->breakto = breaksave;
+
+ EMITS putbranch(fn, end);
+ useblk(fn, begin);
+ doemit = 1;
+ if (!st.bdefault) st.bdefault = end;
+ /* TODO: optimize instead of generating the equivalent of if == .. else if .. chain
+ * 1. sort by case values (also for easy duplicates checking)
+ * 2. contiguous ranges (case a..b: -> x >= && x <= b)
+ * 3. binary search
+ * 4. jump tables? (harder)
+ */
+ for (int i = 0; i < st.cases.n; ++i) {
+ struct swcase c = st.cases.p[i];
+ EMITS {
+ struct block *next = i < st.cases.n - 1 ? newblk(fn) : st.bdefault;
+ putcondbranch(fn, addinstr(fn, mkinstr(Oequ, k, .l = sel, .r = mkintcon(k, c.val))), c.blk, next);
+ useblk(fn, next);
+ }
+ }
+ vfree(&st.cases);
+ if (fn->curblk != end) {
+ EMITS putbranch(fn, end);
+ useblk(fn, end);
+ }
+}
+
static bool /* return 1 if stmt is terminating (ends with a jump) */
stmt(struct comp *cm, struct function *fn)
{
@@ -3142,20 +3204,41 @@ stmt(struct comp *cm, struct function *fn)
bool terminates = 0;
bool doemit = fn->curblk;
-#define EMITS if (doemit && !nerror)
-
- while (match(cm, &tk, TKIDENT)) {
- if (match(cm, NULL, ':')){
+ while (match(cm, &tk, TKIDENT) || match(cm, &tk, TKWcase) || match(cm, &tk, TKWdefault)) {
+ if (tk.t == TKWcase) {
+ /* case <expr> ':' */
+ if (!cm->switchstmt) error(&tk.span, "'case' outside of switch statement");
+ ex = commaexpr(cm);
+ if (!eval(&ex, EVINTCONST)) error(&ex.span, "not an integer constant expression");
+ expect(cm, ':', NULL);
+ begin = newblk(fn);
+ EMITS putbranch(fn, begin);
+ useblk(fn, begin);
+ if (cm->switchstmt)
+ vpush(&cm->switchstmt->cases, ((struct swcase) {ex.i, fn->curblk}));
+ } else if (tk.t == TKWdefault) {
+ /* default ':' */
+ if (!cm->switchstmt) error(&tk.span, "'default' outside of switch statement");
+ expect(cm, ':', NULL);
+ begin = newblk(fn);
+ EMITS putbranch(fn, begin);
+ useblk(fn, begin);
+ if (cm->switchstmt) {
+ if (cm->switchstmt->bdefault) error(&tk.span, "multiple 'default' labels in one switch");
+ cm->switchstmt->bdefault = begin;
+ }
+ } else if (tk.t == TKIDENT && match(cm, NULL, ':')) {
/* <label> ':' */
deflabel(cm, fn, &tk.span, tk.s);
- doemit = 1;
} else {
+ assert(tk.t == TKIDENT);
/* kludge for no backtracking and no lookahead */
- ex = exprparse(cm, 1, &tk);
+ ex = exprparse(cm, 1, &tk, 1);
stmtterm(cm);
EMITS expreffects(fn, &ex);
return fn->curblk == NULL;
}
+ doemit = 1;
}
switch (peek(cm, NULL)) {
@@ -3341,11 +3424,20 @@ stmt(struct comp *cm, struct function *fn)
}
envup(cm);
break;
+ case TKWswitch:
+ lex(cm, NULL);
+ expect(cm, '(', NULL);
+ ex = commaexpr(cm);
+ expect(cm, ')', NULL);
+ if (!isint(ex.ty))
+ error(&ex.span, "'switch' value is not an integer: '%ty'", ex.ty);
+ genswitch(cm, fn, &ex);
+ break;
case TKWbreak:
lex(cm, &tk);
if (!cm->loopdepth && !cm->switchdepth)
error(&tk.span, "'break' outside of loop or switch statement");
- EMITS putbranch(fn, cm->loopbreak);
+ EMITS putbranch(fn, cm->breakto);
stmtterm(cm);
break;
case TKWcontinue:
@@ -3400,7 +3492,7 @@ stmt(struct comp *cm, struct function *fn)
stmtterm(cm);
break;
default:
- ex = commaexpr(cm);
+ ex = exprparse(cm, 1, NULL, 1);
stmtterm(cm);
EMITS expreffects(fn, &ex);
break;
generated by cgit v1.2.3 (git 2.39.1) at 2026-05-02 02:17:31 +0000