Commit 60d47101 authored by Russ Cox's avatar Russ Cox

gc: fix label recursion bugs

Was keeping a pointer to the labeled statement in n->right,
which meant that generic traversals of the tree visited it twice.
That combined with aggressive flattening of the block
structure when possible during parsing meant that
the kinds of label: code label: code label: code sequences
generated by yacc were giving the recursion 2ⁿ paths
through the program.

Fixes #2212.

R=lvd
CC=golang-dev
https://golang.org/cl/4960050
parent ae502c4e
......@@ -287,7 +287,7 @@ stmtlabel(Node *n)
if(n->sym != S)
if((lab = n->sym->label) != L)
if(lab->def != N)
if(lab->def->right == n)
if(lab->def->defn == n)
return lab;
return L;
}
......@@ -355,13 +355,13 @@ gen(Node *n)
if(lab->labelpc == P)
lab->labelpc = pc;
if(n->right) {
switch(n->right->op) {
if(n->defn) {
switch(n->defn->op) {
case OFOR:
case OSWITCH:
case OSELECT:
// so stmtlabel can find the label
n->right->sym = lab->sym;
n->defn->sym = lab->sym;
}
}
break;
......
......@@ -286,7 +286,7 @@ struct Node
// ONAME
Node* ntype;
Node* defn;
Node* defn; // ONAME: initializing assignment; OLABEL: labeled statement
Node* pack; // real package for import . names
Node* curfn; // function for local variables
Type* paramfld; // TFIELD for this PPARAM
......
......@@ -1496,7 +1496,7 @@ non_dcl_stmt:
{
NodeList *l;
$1->right = $4;
$1->defn = $4;
l = list1($1);
if($4)
l = list(l, $4);
......
......@@ -3446,8 +3446,13 @@ list1(Node *n)
if(n == nil)
return nil;
if(n->op == OBLOCK && n->ninit == nil)
return n->list;
if(n->op == OBLOCK && n->ninit == nil) {
// Flatten list and steal storage.
// Poison pointer to catch errant uses.
l = n->list;
n->list = (NodeList*)1;
return l;
}
l = mal(sizeof *l);
l->n = n;
l->end = l;
......
......@@ -780,3 +780,208 @@ func external(*int)
func foo119(x *int) { // ERROR "leaking param: NAME-x"
external(x)
}
func foo120() {
// formerly exponential time analysis
L1:
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// use the labels to silence compiler errors
goto L1
goto L2
goto L3
goto L4
goto L5
goto L6
goto L7
goto L8
goto L9
goto L10
goto L11
goto L12
goto L13
goto L14
goto L15
goto L16
goto L17
goto L18
goto L19
goto L20
goto L21
goto L22
goto L23
goto L24
goto L25
goto L26
goto L27
goto L28
goto L29
goto L30
goto L31
goto L32
goto L33
goto L34
goto L35
goto L36
goto L37
goto L38
goto L39
goto L40
goto L41
goto L42
goto L43
goto L44
goto L45
goto L46
goto L47
goto L48
goto L49
goto L50
goto L51
goto L52
goto L53
goto L54
goto L55
goto L56
goto L57
goto L58
goto L59
goto L60
goto L61
goto L62
goto L63
goto L64
goto L65
goto L66
goto L67
goto L68
goto L69
goto L70
goto L71
goto L72
goto L73
goto L74
goto L75
goto L76
goto L77
goto L78
goto L79
goto L80
goto L81
goto L82
goto L83
goto L84
goto L85
goto L86
goto L87
goto L88
goto L89
goto L90
goto L91
goto L92
goto L93
goto L94
goto L95
goto L96
goto L97
goto L98
goto L99
goto L100
}
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