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/asm_arm.s b/src/pkg/runtime/cgo/asm_arm.s
index 850b1c6..b989ab9 100644
--- a/src/pkg/runtime/cgo/asm_arm.s
+++ b/src/pkg/runtime/cgo/asm_arm.s
@@ -14,11 +14,11 @@
* push 2 args for fn (R1 and R2).
* Also note that at procedure entry in 5c/5g world, 4(R13) will be the
* first arg, so we must push another dummy reg (R0) for 0(R13).
- * Additionally, runtime·load_gm will clobber R0, so we need to save R0
+ * Additionally, runtime·load_g will clobber R0, so we need to save R0
* nevertheless.
*/
- MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, R14], (R13)
- BL runtime·load_gm(SB)
+ MOVM.WP [R0, R1, R2, R4, R5, R6, R7, R8, R9, g, R11, R12, R14], (R13)
+ BL runtime·load_g(SB)
MOVW PC, R14
MOVW 0(R13), PC
- MOVM.IAW (R13), [R0, R1, R2, R4, R5, R6, R7, R8, m, g, R11, R12, PC]
+ MOVM.IAW (R13), [R0, R1, R2, R4, R5, R6, R7, R8, R9, g, R11, R12, PC]
