build: disable precise collection of stack frames

The code for call site-specific pointer bitmaps was not ready in time,
but the zeroing required without it is too expensive to use by default.
We will have to wait for precise collection of stack frames until Go 1.3.

The precise collection can be re-enabled by

        GOEXPERIMENT=precisestack ./all.bash

but that will not be the default for a Go 1.2 build.

Fixes #6087.

R=golang-dev, jeremyjackins, dan.kortschak, r
CC=golang-dev
https://golang.org/cl/13677045

diff --git a/src/cmd/dist/a.h b/src/cmd/dist/a.h
index 4a3ec803606e25296efe35ae4cb3469c1e34fcd0..0f46a43166b687ec2347176fe68667c2a80ecc98 100644 (file)
--- a/src/cmd/dist/a.h
+++ b/src/cmd/dist/a.h
@@ -101,6 +101,7 @@ void        mkzgoarch(char*, char*);
 void   mkzgoos(char*, char*);
 void   mkzruntimedefs(char*, char*);
 void   mkzversion(char*, char*);
+void   mkzexperiment(char*, char*);
 
 // buildgo.c
 void   mkzdefaultcc(char*, char*);

diff --git a/src/cmd/dist/build.c b/src/cmd/dist/build.c
index f46771d20d556aee80ec2b119cd8c6e1f85f7954..0fe951fc0ee5926b56eda3271114bf02b7f323d0 100644 (file)
--- a/src/cmd/dist/build.c
+++ b/src/cmd/dist/build.c
@@ -557,6 +557,7 @@ static struct {
                "$GOROOT/pkg/obj/$GOOS_$GOARCH/lib9.a",
        }},
        {"pkg/runtime", {
+               "zaexperiment.h", // must sort above zasm
                "zasm_$GOOS_$GOARCH.h",
                "zsys_$GOOS_$GOARCH.s",
                "zgoarch_$GOARCH.go",
@@ -589,6 +590,7 @@ static struct {
        {"zgoos_", mkzgoos},
        {"zruntime_defs_", mkzruntimedefs},
        {"zversion.go", mkzversion},
+       {"zaexperiment.h", mkzexperiment},
 };
 
 // install installs the library, package, or binary associated with dir,

diff --git a/src/cmd/dist/buildruntime.c b/src/cmd/dist/buildruntime.c
index 62ec8b60e5df62c308c1a6aff0ccc4551b2f1984..e6e309d92a4b059227474099da55855aeb0e1071 100644 (file)
--- a/src/cmd/dist/buildruntime.c
+++ b/src/cmd/dist/buildruntime.c
@@ -38,6 +38,34 @@ mkzversion(char *dir, char *file)
        bfree(&out);
 }
 
+// mkzexperiment writes zaexperiment.h (sic):
+//
+//     #define GOEXPERIMENT "experiment string"
+//
+void
+mkzexperiment(char *dir, char *file)
+{
+       Buf b, out, exp;
+       
+       USED(dir);
+
+       binit(&b);
+       binit(&out);
+       binit(&exp);
+       
+       xgetenv(&exp, "GOEXPERIMENT");
+       bwritestr(&out, bprintf(&b,
+               "// auto generated by go tool dist\n"
+               "\n"
+               "#define GOEXPERIMENT \"%s\"\n", bstr(&exp)));
+
+       writefile(&out, file, 0);
+       
+       bfree(&b);
+       bfree(&out);
+       bfree(&exp);
+}
+
 // mkzgoarch writes zgoarch_$GOARCH.go:
 //
 //     package runtime
@@ -193,12 +221,13 @@ mkzasm(char *dir, char *file)
 {
        int i, n;
        char *aggr, *p;
-       Buf in, b, out;
+       Buf in, b, out, exp;
        Vec argv, lines, fields;
 
        binit(&in);
        binit(&b);
        binit(&out);
+       binit(&exp);
        vinit(&argv);
        vinit(&lines);
        vinit(&fields);
@@ -284,6 +313,9 @@ ok:
                bwritestr(&out, bprintf(&b, "#define cb_max %d\n", MAXWINCB));
        }
        
+       xgetenv(&exp, "GOEXPERIMENT");
+       bwritestr(&out, bprintf(&b, "#define GOEXPERIMENT \"%s\"\n", bstr(&exp)));
+       
        // Write both to file and to workdir/zasm_GOOS_GOARCH.h.
        writefile(&out, file, 0);
        writefile(&out, bprintf(&b, "%s/zasm_GOOS_GOARCH.h", workdir), 0);
@@ -291,6 +323,7 @@ ok:
        bfree(&in);
        bfree(&b);
        bfree(&out);
+       bfree(&exp);
        vfree(&argv);
        vfree(&lines);
        vfree(&fields);

diff --git a/src/cmd/gc/go.h b/src/cmd/gc/go.h
index 59e241bbe3209f1515864e1d2cb7763422107104..77045858829870bd00e7ffcb7d4d3880245cef87 100644 (file)
--- a/src/cmd/gc/go.h
+++ b/src/cmd/gc/go.h
@@ -982,6 +982,7 @@ EXTERN      int     noescape;
 
 EXTERN int     nointerface;
 EXTERN int     fieldtrack_enabled;
+EXTERN int     precisestack_enabled;
 
 /*
  *     y.tab.c

diff --git a/src/cmd/gc/lex.c b/src/cmd/gc/lex.c
index f4a6e0503e578e299e4741e9118b2473500c5113..414456adf2e84fc4f511667d2f4ca1eb7e30347c 100644 (file)
--- a/src/cmd/gc/lex.c
+++ b/src/cmd/gc/lex.c
@@ -41,6 +41,7 @@ static struct {
 } exper[] = {
 //     {"rune32", &rune32},
        {"fieldtrack", &fieldtrack_enabled},
+       {"precisestack", &precisestack_enabled},
        {nil, nil},
 };
 

diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index 0fbac84cf606534466ecac4f3539cec1b945b812..7ea76fc5fc0e671c17dbc7f996d25ff4440ce53f 100644 (file)
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -316,7 +316,7 @@ walktype(Type *type, Bvec *bv)
        walktype1(type, &xoffset, bv);
 }
 
-// Compute a bit vector to describes the pointer containing locations
+// Compute a bit vector to describe the pointer-containing locations
 // in the in and out argument list and dump the bitvector length and
 // data to the provided symbol.
 static void
@@ -344,9 +344,9 @@ dumpgcargs(Node *fn, Sym *sym)
        ggloblsym(sym, off, 0, 1);
 }
 
-// Compute a bit vector to describes the pointer containing locations
-// in local variables and dumps the bitvector length and data out to
-// the provided symbol. Returns the vector for use and freeing by caller.
+// Compute a bit vector to describe the pointer-containing locations
+// in local variables and dump the bitvector length and data out to
+// the provided symbol. Return the vector for use and freeing by caller.
 static Bvec*
 dumpgclocals(Node* fn, Sym *sym)
 {
@@ -438,11 +438,13 @@ allocauto(Prog* ptxt)
                        ll->n->used = 0;
 
        markautoused(ptxt);
-       
-       // TODO: Remove when liveness analysis sets needzero instead.
-       for(ll=curfn->dcl; ll != nil; ll=ll->next)
-               if (ll->n->class == PAUTO)
-                       ll->n->needzero = 1; // ll->n->addrtaken;
+
+       if(precisestack_enabled) {
+               // TODO: Remove when liveness analysis sets needzero instead.
+               for(ll=curfn->dcl; ll != nil; ll=ll->next)
+                       if(ll->n->class == PAUTO)
+                               ll->n->needzero = 1; // ll->n->addrtaken;
+       }
 
        listsort(&curfn->dcl, cmpstackvar);
 

diff --git a/src/cmd/gc/walk.c b/src/cmd/gc/walk.c
index 489b947143ae0efbe27e0f7493dfb743c1139df5..a1172b87ef0961d1f5588f7d8e06730ccddaefe3 100644 (file)
--- a/src/cmd/gc/walk.c
+++ b/src/cmd/gc/walk.c
@@ -2331,9 +2331,9 @@ paramstoheap(Type **argin, int out)
                v = t->nname;
                if(v && v->sym && v->sym->name[0] == '~')
                        v = N;
-               // The garbage collector assumes results are always live,
-               // so zero them always (1 ||).
-               if(out && (1 || (v == N && hasdefer))) {
+               // In precisestack mode, the garbage collector assumes results
+               // are always live, so zero them always.
+               if(out && (precisestack_enabled || (v == N && hasdefer))) {
                        // Defer might stop a panic and show the
                        // return values as they exist at the time of panic.
                        // Make sure to zero them on entry to the function.

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index 9b6a9d5e9627e4843c3b4d509db42997263d6ee9..fe9c18177c96f7ea34f3300579247ebb748d4c74 100644 (file)
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -1345,7 +1345,7 @@ scaninterfacedata(uintptr bits, byte *scanp, bool afterprologue)
        Itab *tab;
        Type *type;
 
-       if(afterprologue) {
+       if(runtime·precisestack && afterprologue) {
                if(bits == BitsIface) {
                        tab = *(Itab**)scanp;
                        if(tab->type->size <= sizeof(void*) && (tab->type->kind & KindNoPointers))

diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 07515c54f94784672555a975b7b41a32c6ae0785..e34e9e5067bb1fd1ad92a7f4d87d0d424f6d2967 100644 (file)
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -4,6 +4,7 @@
 
 #include "runtime.h"
 #include "arch_GOARCH.h"
+#include "zaexperiment.h"
 #include "malloc.h"
 #include "stack.h"
 #include "race.h"
@@ -112,6 +113,7 @@ static void injectglist(G*);
 static bool preemptall(void);
 static bool preemptone(P*);
 static bool exitsyscallfast(void);
+static bool haveexperiment(int8*);
 
 // The bootstrap sequence is:
 //
@@ -128,6 +130,7 @@ runtime·schedinit(void)
        byte *p;
 
        runtime·sched.maxmcount = 10000;
+       runtime·precisestack = haveexperiment("precisestack");
 
        m->nomemprof++;
        runtime·mprofinit();
@@ -2929,3 +2932,24 @@ runtime∕debug·setMaxThreads(intgo in, intgo out)
        runtime·unlock(&runtime·sched);
        FLUSH(&out);
 }
+
+static int8 experiment[] = GOEXPERIMENT; // defined in zaexperiment.h
+
+static bool
+haveexperiment(int8 *name)
+{
+       int32 i, j;
+       
+       for(i=0; i<sizeof(experiment); i++) {
+               if((i == 0 || experiment[i-1] == ',') && experiment[i] == name[0]) {
+                       for(j=0; name[j]; j++)
+                               if(experiment[i+j] != name[j])
+                                       goto nomatch;
+                       if(experiment[i+j] != '\0' && experiment[i+j] != ',')
+                               goto nomatch;
+                       return 1;
+               }
+       nomatch:;
+       }
+       return 0;
+}

diff --git a/src/pkg/runtime/runtime.h b/src/pkg/runtime/runtime.h
index 9974fa32691475b89a26f7ad6a1b2e4e872e36b1..920e86c3120964d8687827e61c128f493bdc75e9 100644 (file)
--- a/src/pkg/runtime/runtime.h
+++ b/src/pkg/runtime/runtime.h
@@ -539,6 +539,8 @@ struct DebugVars
        int32   scheddetail;
 };
 
+extern bool runtime·precisestack;
+
 /*
  * defined macros
  *    you need super-gopher-guru privilege