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

diff --git a/src/cmd/gc/gen.c b/src/cmd/gc/gen.c
index 7dbe2c4cb8524e07e7a37826f3dff9b447828b14..d585c451a282726f189e159080e956f1f0f799f0 100644 (file)
--- a/src/cmd/gc/gen.c
+++ b/src/cmd/gc/gen.c
@@ -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;

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 4367c9cb40e6a7c774c95a0b5d960ae332b16776..42f2140255b558ba587517c9b984fc37c6089f63 100644 (file)
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -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

diff --git a/src/cmd/gc/go.y b/src/cmd/gc/go.y
index 373d42f136526c57437741d6dae072873e8a3550..2ec8d888b50a2977438ecbcf9f1d5971a490b1a5 100644 (file)
--- a/src/cmd/gc/go.y
+++ b/src/cmd/gc/go.y
@@ -1496,7 +1496,7 @@ non_dcl_stmt:
        {
                NodeList *l;
 
-               $1->right = $4;
+               $1->defn = $4;
                l = list1($1);
                if($4)
                        l = list(l, $4);

diff --git a/src/cmd/gc/subr.c b/src/cmd/gc/subr.c
index 795c1281094b76d810c5c936b1b829c3f2811f20..5ebb150212e32e614e5df819fdd7cb24f7a7401d 100644 (file)
--- a/src/cmd/gc/subr.c
+++ b/src/cmd/gc/subr.c
@@ -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;

diff --git a/test/escape2.go b/test/escape2.go
index 0b78624b6c8dd03c859b7c6ae4107b7f17d3525d..c21a188308fde66df84270e14245f04e216a1630 100644 (file)
--- a/test/escape2.go
+++ b/test/escape2.go
@@ -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:
+L2:
+L3:
+L4:
+L5:
+L6:
+L7:
+L8:
+L9:
+L10:
+L11:
+L12:
+L13:
+L14:
+L15:
+L16:
+L17:
+L18:
+L19:
+L20:
+L21:
+L22:
+L23:
+L24:
+L25:
+L26:
+L27:
+L28:
+L29:
+L30:
+L31:
+L32:
+L33:
+L34:
+L35:
+L36:
+L37:
+L38:
+L39:
+L40:
+L41:
+L42:
+L43:
+L44:
+L45:
+L46:
+L47:
+L48:
+L49:
+L50:
+L51:
+L52:
+L53:
+L54:
+L55:
+L56:
+L57:
+L58:
+L59:
+L60:
+L61:
+L62:
+L63:
+L64:
+L65:
+L66:
+L67:
+L68:
+L69:
+L70:
+L71:
+L72:
+L73:
+L74:
+L75:
+L76:
+L77:
+L78:
+L79:
+L80:
+L81:
+L82:
+L83:
+L84:
+L85:
+L86:
+L87:
+L88:
+L89:
+L90:
+L91:
+L92:
+L93:
+L94:
+L95:
+L96:
+L97:
+L98:
+L99:
+L100:
+       // 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
+}