all: remove 'extern register M *m' from runtime
The runtime has historically held two dedicated values g (current goroutine)
and m (current thread) in 'extern register' slots (TLS on x86, real registers
backed by TLS on ARM).
This CL removes the extern register m; code now uses g->m.
On ARM, this frees up the register that formerly held m (R9).
This is important for NaCl, because NaCl ARM code cannot use R9 at all.
The Go 1 macrobenchmarks (those with per-op times >= 10 µs) are unaffected:
BenchmarkBinaryTree17 5491374955 5471024381 -0.37%
BenchmarkFannkuch11 4357101311 4275174828 -1.88%
BenchmarkGobDecode 11029957 11364184 +3.03%
BenchmarkGobEncode 6852205 6784822 -0.98%
BenchmarkGzip 650795967 650152275 -0.10%
BenchmarkGunzip 140962363 141041670 +0.06%
BenchmarkHTTPClientServer 71581 73081 +2.10%
BenchmarkJSONEncode 31928079 31913356 -0.05%
BenchmarkJSONDecode 117470065 113689916 -3.22%
BenchmarkMandelbrot200 6008923 5998712 -0.17%
BenchmarkGoParse 6310917 6327487 +0.26%
BenchmarkRegexpMatchMedium_1K 114568 114763 +0.17%
BenchmarkRegexpMatchHard_1K 168977 169244 +0.16%
BenchmarkRevcomp 935294971 914060918 -2.27%
BenchmarkTemplate 145917123 148186096 +1.55%
Minux previous reported larger variations, but these were caused by
run-to-run noise, not repeatable slowdowns.
Actual code changes by Minux.
I only did the docs and the benchmarking.
LGTM=dvyukov, iant, minux
R=minux, josharian, iant, dave, bradfitz, dvyukov
CC=golang-codereviews
https://golang.org/cl/109050043
diff --git a/src/pkg/runtime/cgo/gcc_openbsd_amd64.c b/src/pkg/runtime/cgo/gcc_openbsd_amd64.c
index 64d29a9..5f0d3bb 100644
--- a/src/pkg/runtime/cgo/gcc_openbsd_amd64.c
+++ b/src/pkg/runtime/cgo/gcc_openbsd_amd64.c
@@ -11,7 +11,7 @@
#include "libcgo.h"
static void* threadentry(void*);
-static void (*setmg_gcc)(void*, void*);
+static void (*setg_gcc)(void*);
// TCB_SIZE is sizeof(struct thread_control_block),
// as defined in /usr/src/lib/librthread/tcb.h
@@ -83,13 +83,13 @@
}
void
-x_cgo_init(G *g, void (*setmg)(void*, void*))
+x_cgo_init(G *g, void (*setg)(void*))
{
pthread_attr_t attr;
size_t size;
void *handle;
- setmg_gcc = setmg;
+ setg_gcc = setg;
pthread_attr_init(&attr);
pthread_attr_getstacksize(&attr, &size);
g->stackguard = (uintptr)&attr - size + 4096;
@@ -159,7 +159,7 @@
/*
* Set specific keys.
*/
- setmg_gcc((void*)ts.m, (void*)ts.g);
+ setg_gcc((void*)ts.g);
crosscall_amd64(ts.fn);
return nil;
