From 037a1a9f3183e92a930e25ce66dba99df3786fb0 Mon Sep 17 00:00:00 2001
From: Carl Shapiro <cshapiro@google.com>
Date: Wed, 29 May 2013 17:16:57 -0700
Subject: [PATCH] cmd/ld, runtime: emit pointer maps for nosplits identified by
 the linker

A nosplits was assumed to have no argument information and no
pointer map.  However, nosplits created by the linker often
have both.  This change uses the pointer map size as an
alternate source of argument size when processing a nosplit.

In addition, the symbol table construction pointer map size
and argument size consistency check is strengthened.  If a
nptrs is greater than 0 it must be equal to the number of
argument words.

R=golang-dev, khr, khr
CC=golang-dev
https://golang.org/cl/9666047
---
 src/cmd/gc/pgen.c        | 22 ++++++++--------------
 src/cmd/ld/lib.c         |  6 +++++-
 src/pkg/runtime/symtab.c |  4 ++--
 3 files changed, 15 insertions(+), 17 deletions(-)

diff --git a/src/cmd/gc/pgen.c b/src/cmd/gc/pgen.c
index 7fcbf19b1e..4d3859d02d 100644
--- a/src/cmd/gc/pgen.c
+++ b/src/cmd/gc/pgen.c
@@ -296,21 +296,15 @@ pointermap(Node *fn)
 		walktype(inargtype, bv);
 	if(outargtype != nil)
 		walktype(outargtype, bv);
-	if(bvisempty(bv)) {
-		prog = gins(ANPTRS, N, N);
+	prog = gins(ANPTRS, N, N);
+	prog->to.type = D_CONST;
+	prog->to.offset = bv->n;
+	for(i = 0; i < bv->n; i += 32) {
+		prog = gins(APTRS, N, N);
+		prog->from.type = D_CONST;
+		prog->from.offset = i / 32;
 		prog->to.type = D_CONST;
-		prog->to.offset = 0;
-	} else {
-		prog = gins(ANPTRS, N, N);
-		prog->to.type = D_CONST;
-		prog->to.offset = bv->n;
-		for(i = 0; i < bv->n; i += 32) {
-			prog = gins(APTRS, N, N);
-			prog->from.type = D_CONST;
-			prog->from.offset = i / 32;
-			prog->to.type = D_CONST;
-			prog->to.offset = bv->b[i / 32];
-		}
+		prog->to.offset = bv->b[i / 32];
 	}
 	free(bv);
 }
diff --git a/src/cmd/ld/lib.c b/src/cmd/ld/lib.c
index 42448fe09f..88c9f6a607 100644
--- a/src/cmd/ld/lib.c
+++ b/src/cmd/ld/lib.c
@@ -1914,7 +1914,11 @@ genasmsym(void (*put)(Sym*, char*, int, vlong, vlong, int, Sym*))
 		/* frame, locals, args, auto, param and pointers after */
 		put(nil, ".frame", 'm', (uint32)s->text->to.offset+PtrSize, 0, 0, 0);
 		put(nil, ".locals", 'm', s->locals, 0, 0, 0);
-		if(s->text->textflag & NOSPLIT)
+		if((s->text->textflag & NOSPLIT) && (s->args == 0) && (s->nptrs < 0))
+			// This might be a vararg function and have no
+			// predetermined argument size.  This check is
+			// approximate and will also match 0 argument
+			// nosplit functions compiled by 6c.
 			put(nil, ".args", 'm', ArgsSizeUnknown, 0, 0, 0);
 		else
 			put(nil, ".args", 'm', s->args, 0, 0, 0);
diff --git a/src/pkg/runtime/symtab.c b/src/pkg/runtime/symtab.c
index be06d578d4..ffcb8826e6 100644
--- a/src/pkg/runtime/symtab.c
+++ b/src/pkg/runtime/symtab.c
@@ -234,8 +234,8 @@ dofunc(Sym *sym)
 			func[nfunc-1].args = sym->value;
 		else if(runtime·strcmp(sym->name, (byte*)".nptrs") == 0) {
 			// TODO(cshapiro): use a dense representation for gc information
-			if(sym->value > func[nfunc-1].args/sizeof(uintptr)) {
-				runtime·printf("more pointer map entries than argument words\n");
+			if(sym->value != func[nfunc-1].args/sizeof(uintptr)) {
+				runtime·printf("pointer map size and argument size disagree\n");
 				runtime·throw("mangled symbol table");
 			}
 			cap = ROUND(sym->value, 32) / 32;
-- 
2.48.1