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/sys_plan9_386.s b/src/pkg/runtime/sys_plan9_386.s
index 143cd2e..5a652ab 100644
--- a/src/pkg/runtime/sys_plan9_386.s
+++ b/src/pkg/runtime/sys_plan9_386.s
@@ -98,7 +98,7 @@
// Initialize m, g.
get_tls(AX)
MOVL DX, g(AX)
- MOVL BX, m(AX)
+ MOVL BX, g_m(DX)
// Initialize procid from TOS struct.
// TODO: Be explicit and insert a new MOVL _tos(SB), AX here.
@@ -123,8 +123,8 @@
TEXT runtime·sigtramp(SB),NOSPLIT,$0
get_tls(AX)
- // check that m exists
- MOVL m(AX), BX
+ // check that g exists
+ MOVL g(AX), BX
CMPL BX, $0
JNE 3(PC)
CALL runtime·badsignal2(SB) // will exit
@@ -135,6 +135,7 @@
MOVL note+8(SP), DX
// change stack
+ MOVL g_m(BX), BX
MOVL m_gsignal(BX), BP
MOVL g_stackbase(BP), BP
MOVL BP, SP
@@ -181,7 +182,8 @@
// See ../syscall/asm_plan9_386.s:/·Syscall/
TEXT runtime·errstr(SB),NOSPLIT,$0
get_tls(AX)
- MOVL m(AX), BX
+ MOVL g(AX), BX
+ MOVL g_m(BX), BX
MOVL m_errstr(BX), CX
MOVL CX, 4(SP)
MOVL $ERRMAX, 8(SP)
