cmd, runtime: remove PC_F & PC_B globals on Wasm
Following the previous CL, this removes more global variables on
Wasm.
PC_B is used mostly for intra-function jumps, and for a function
telling its callee where to start or resume. This usage can be
served by a parameter. The top level loop (wasm_pc_f_loop) uses
PC_B for resuming a function. This value is either set by gogo,
or loaded from the Go stack at function return. Instead of
loading PC_B at each function return, we could make gogo stores
PC_B at the same stack location, and let the top level loop do
the load. This way, we don't need to use global PC_B to
communicate with the top level loop, and we can replace global
PC_B with a parameter.
PC_F is similar. It is even more so in that the only reader is
the top level loop. Let the top level loop read it from the stack,
and we can get rid of PC_F entirely.
PC_F and PC_B are used less entensively as SP, so this CL has
smaller performance gain.
Running on Chrome 74.0.3729.108 on Linux/AMD64,
name old time/op new time/op delta
BinaryTree17 16.6s ± 0% 16.2s ± 1% -2.59% (p=0.016 n=4+5)
Fannkuch11 11.1s ± 1% 10.8s ± 0% -2.65% (p=0.008 n=5+5)
FmtFprintfEmpty 231ns ± 1% 217ns ± 0% -6.06% (p=0.008 n=5+5)
FmtFprintfString 407ns ± 3% 375ns ± 2% -7.81% (p=0.008 n=5+5)
FmtFprintfInt 466ns ± 2% 430ns ± 0% -7.79% (p=0.016 n=5+4)
FmtFprintfIntInt 719ns ± 2% 673ns ± 2% -6.37% (p=0.008 n=5+5)
FmtFprintfPrefixedInt 706ns ± 1% 676ns ± 3% -4.31% (p=0.008 n=5+5)
FmtFprintfFloat 1.01µs ± 1% 0.97µs ± 1% -4.30% (p=0.008 n=5+5)
FmtManyArgs 2.67µs ± 1% 2.51µs ± 1% -5.95% (p=0.008 n=5+5)
GobDecode 30.7ms ± 9% 31.3ms ±34% ~ (p=0.222 n=5+5)
GobEncode 24.2ms ±23% 20.2ms ± 0% -16.36% (p=0.016 n=5+4)
Gzip 852ms ± 0% 823ms ± 0% -3.38% (p=0.016 n=4+5)
Gunzip 160ms ± 1% 151ms ± 1% -5.37% (p=0.008 n=5+5)
JSONEncode 35.7ms ± 1% 34.3ms ± 1% -3.81% (p=0.008 n=5+5)
JSONDecode 247ms ± 8% 254ms ± 7% ~ (p=0.548 n=5+5)
Mandelbrot200 5.39ms ± 0% 5.41ms ± 0% +0.42% (p=0.008 n=5+5)
GoParse 18.5ms ± 1% 18.3ms ± 2% ~ (p=0.343 n=4+4)
RegexpMatchEasy0_32 424ns ± 2% 397ns ± 0% -6.23% (p=0.008 n=5+5)
RegexpMatchEasy0_1K 2.88µs ± 0% 2.86µs ± 1% ~ (p=0.079 n=5+5)
RegexpMatchEasy1_32 395ns ± 2% 370ns ± 1% -6.23% (p=0.008 n=5+5)
RegexpMatchEasy1_1K 3.26µs ± 0% 3.19µs ± 1% -2.06% (p=0.008 n=5+5)
RegexpMatchMedium_32 564ns ± 1% 532ns ± 0% -5.71% (p=0.008 n=5+5)
RegexpMatchMedium_1K 146µs ± 2% 140µs ± 1% -4.62% (p=0.008 n=5+5)
RegexpMatchHard_32 8.47µs ± 1% 7.91µs ± 1% -6.65% (p=0.008 n=5+5)
RegexpMatchHard_1K 253µs ± 1% 236µs ± 2% -6.66% (p=0.008 n=5+5)
Revcomp 1.78s ± 4% 1.76s ± 5% ~ (p=1.000 n=5+5)
Template 292ms ±29% 269ms ± 5% ~ (p=0.690 n=5+5)
TimeParse 1.61µs ± 4% 1.54µs ± 1% -4.42% (p=0.008 n=5+5)
TimeFormat 1.66µs ± 3% 1.58µs ± 1% -5.22% (p=0.008 n=5+5)
[Geo mean] 232µs 221µs -4.54%
name old speed new speed delta
GobDecode 25.0MB/s ± 8% 25.1MB/s ±27% ~ (p=0.222 n=5+5)
GobEncode 32.8MB/s ±21% 38.0MB/s ± 0% +15.84% (p=0.016 n=5+4)
Gzip 22.8MB/s ± 0% 23.6MB/s ± 0% +3.49% (p=0.016 n=4+5)
Gunzip 121MB/s ± 1% 128MB/s ± 1% +5.68% (p=0.008 n=5+5)
JSONEncode 54.4MB/s ± 1% 56.5MB/s ± 1% +3.97% (p=0.008 n=5+5)
JSONDecode 7.88MB/s ± 8% 7.65MB/s ± 8% ~ (p=0.548 n=5+5)
GoParse 3.07MB/s ± 8% 3.00MB/s ±22% ~ (p=0.579 n=5+5)
RegexpMatchEasy0_32 75.6MB/s ± 2% 80.5MB/s ± 0% +6.58% (p=0.008 n=5+5)
RegexpMatchEasy0_1K 356MB/s ± 0% 358MB/s ± 1% ~ (p=0.095 n=5+5)
RegexpMatchEasy1_32 81.1MB/s ± 2% 86.5MB/s ± 1% +6.69% (p=0.008 n=5+5)
RegexpMatchEasy1_1K 314MB/s ± 0% 320MB/s ± 0% +2.10% (p=0.008 n=5+5)
RegexpMatchMedium_32 1.77MB/s ± 1% 1.88MB/s ± 0% +6.09% (p=0.016 n=5+4)
RegexpMatchMedium_1K 6.99MB/s ± 2% 7.33MB/s ± 1% +4.83% (p=0.008 n=5+5)
RegexpMatchHard_32 3.78MB/s ± 1% 4.04MB/s ± 1% +7.04% (p=0.008 n=5+5)
RegexpMatchHard_1K 4.04MB/s ± 1% 4.33MB/s ± 2% +7.17% (p=0.008 n=5+5)
Revcomp 143MB/s ± 4% 145MB/s ± 5% ~ (p=1.000 n=5+5)
Template 6.77MB/s ±24% 7.22MB/s ± 5% ~ (p=0.690 n=5+5)
[Geo mean] 24.4MB/s 25.4MB/s +4.18%
Change-Id: Ib80716e62992aec28b2c4a96af280c278f83aa49
Reviewed-on: https://go-review.googlesource.com/c/go/+/173980
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Richard Musiol <neelance@gmail.com>
diff --git a/src/cmd/internal/obj/wasm/a.out.go b/src/cmd/internal/obj/wasm/a.out.go
index c686f1d..823777d 100644
--- a/src/cmd/internal/obj/wasm/a.out.go
+++ b/src/cmd/internal/obj/wasm/a.out.go
@@ -250,9 +250,7 @@
const (
// globals
- REG_PC_F = obj.RBaseWasm + iota
- REG_PC_B
- REG_SP // SP is currently 32-bit, until 64-bit memory operations are available
+ REG_SP = obj.RBaseWasm + iota // SP is currently 32-bit, until 64-bit memory operations are available
REG_CTXT
REG_g
// RET* are used by runtime.return0 and runtime.reflectcall. These functions pass return values in registers.
@@ -296,9 +294,11 @@
REG_F14
REG_F15
+ REG_PC_B // also first parameter, i32
+
MAXREG
- MINREG = REG_PC_F
+ MINREG = REG_SP
REGSP = REG_SP
REGCTXT = REG_CTXT
REGG = REG_g
diff --git a/src/cmd/internal/obj/wasm/wasmobj.go b/src/cmd/internal/obj/wasm/wasmobj.go
index 0ad8834..a6388b9 100644
--- a/src/cmd/internal/obj/wasm/wasmobj.go
+++ b/src/cmd/internal/obj/wasm/wasmobj.go
@@ -16,8 +16,6 @@
)
var Register = map[string]int16{
- "PC_F": REG_PC_F,
- "PC_B": REG_PC_B,
"SP": REG_SP,
"CTXT": REG_CTXT,
"g": REG_g,
@@ -60,6 +58,8 @@
"F13": REG_F13,
"F14": REG_F14,
"F15": REG_F15,
+
+ "PC_B": REG_PC_B,
}
var registerNames []string
@@ -368,20 +368,31 @@
break
}
- // reset PC_B to function entry
- p = appendp(p, AI32Const, constAddr(0))
- p = appendp(p, ASet, regAddr(REG_PC_B))
-
// low-level WebAssembly call to function
switch jmp.To.Type {
case obj.TYPE_MEM:
+ if !notUsePC_B[jmp.To.Sym.Name] {
+ // Set PC_B parameter to function entry.
+ p = appendp(p, AI32Const, constAddr(0))
+ }
p = appendp(p, ACall, jmp.To)
+
case obj.TYPE_NONE:
// (target PC is on stack)
p = appendp(p, AI32WrapI64)
p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero
p = appendp(p, AI32ShrU)
+
+ // Set PC_B parameter to function entry.
+ // We need to push this before pushing the target PC_F,
+ // so temporarily pop PC_F, using our REG_PC_B as a
+ // scratch register, and push it back after pushing 0.
+ p = appendp(p, ASet, regAddr(REG_PC_B))
+ p = appendp(p, AI32Const, constAddr(0))
+ p = appendp(p, AGet, regAddr(REG_PC_B))
+
p = appendp(p, ACallIndirect)
+
default:
panic("bad target for JMP")
}
@@ -419,20 +430,31 @@
})
p = appendp(p, AI64Store, constAddr(0))
- // reset PC_B to function entry
- p = appendp(p, AI32Const, constAddr(0))
- p = appendp(p, ASet, regAddr(REG_PC_B))
-
// low-level WebAssembly call to function
switch call.To.Type {
case obj.TYPE_MEM:
+ if !notUsePC_B[call.To.Sym.Name] {
+ // Set PC_B parameter to function entry.
+ p = appendp(p, AI32Const, constAddr(0))
+ }
p = appendp(p, ACall, call.To)
+
case obj.TYPE_NONE:
// (target PC is on stack)
p = appendp(p, AI32WrapI64)
p = appendp(p, AI32Const, constAddr(16)) // only needs PC_F bits (16-31), PC_B bits (0-15) are zero
p = appendp(p, AI32ShrU)
+
+ // Set PC_B parameter to function entry.
+ // We need to push this before pushing the target PC_F,
+ // so temporarily pop PC_F, using our PC_B as a
+ // scratch register, and push it back after pushing 0.
+ p = appendp(p, ASet, regAddr(REG_PC_B))
+ p = appendp(p, AI32Const, constAddr(0))
+ p = appendp(p, AGet, regAddr(REG_PC_B))
+
p = appendp(p, ACallIndirect)
+
default:
panic("bad target for CALL")
}
@@ -465,7 +487,13 @@
// jump to before the call if jmpdefer has reset the return address to the call's PC
if call.To.Sym == deferreturn {
- p = appendp(p, AGet, regAddr(REG_PC_B))
+ // get PC_B from -8(SP)
+ p = appendp(p, AGet, regAddr(REG_SP))
+ p = appendp(p, AI32Const, constAddr(8))
+ p = appendp(p, AI32Sub)
+ p = appendp(p, AI32Load16U, constAddr(0))
+ p = appendp(p, ATee, regAddr(REG_PC_B))
+
p = appendp(p, AI32Const, constAddr(call.Pc))
p = appendp(p, AI32Eq)
p = appendp(p, ABrIf, constAddr(0))
@@ -487,9 +515,8 @@
}
if ret.To.Type == obj.TYPE_MEM {
- // reset PC_B to function entry
+ // Set PC_B parameter to function entry.
p = appendp(p, AI32Const, constAddr(0))
- p = appendp(p, ASet, regAddr(REG_PC_B))
// low-level WebAssembly call to function
p = appendp(p, ACall, ret.To)
@@ -497,16 +524,6 @@
break
}
- // read return PC_F from Go stack
- p = appendp(p, AGet, regAddr(REG_SP))
- p = appendp(p, AI32Load16U, constAddr(2))
- p = appendp(p, ASet, regAddr(REG_PC_F))
-
- // read return PC_B from Go stack
- p = appendp(p, AGet, regAddr(REG_SP))
- p = appendp(p, AI32Load16U, constAddr(0))
- p = appendp(p, ASet, regAddr(REG_PC_B))
-
// SP += 8
p = appendp(p, AGet, regAddr(REG_SP))
p = appendp(p, AI32Const, constAddr(8))
@@ -771,16 +788,38 @@
return
}
+// Most of the Go functions has a single parameter (PC_B) in
+// Wasm ABI. This is a list of exceptions.
+var notUsePC_B = map[string]bool{
+ "_rt0_wasm_js": true,
+ "wasm_export_run": true,
+ "wasm_export_resume": true,
+ "wasm_export_getsp": true,
+ "wasm_pc_f_loop": true,
+ "runtime.wasmMove": true,
+ "runtime.wasmZero": true,
+ "runtime.wasmDiv": true,
+ "runtime.wasmTruncS": true,
+ "runtime.wasmTruncU": true,
+ "runtime.gcWriteBarrier": true,
+ "cmpbody": true,
+ "memeqbody": true,
+ "memcmp": true,
+ "memchr": true,
+}
+
func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
w := new(bytes.Buffer)
hasLocalSP := false
+ hasPC_B := false
var r0, f0 int16
// Function starts with declaration of locals: numbers and types.
// Some functions use a special calling convention.
switch s.Name {
- case "wasm_export_run", "runtime.wasmMove", "runtime.wasmZero", "runtime.wasmDiv", "runtime.wasmTruncS", "runtime.wasmTruncU", "memeqbody":
+ case "_rt0_wasm_js", "wasm_export_run", "wasm_export_resume", "wasm_export_getsp", "wasm_pc_f_loop",
+ "runtime.wasmMove", "runtime.wasmZero", "runtime.wasmDiv", "runtime.wasmTruncS", "runtime.wasmTruncU", "memeqbody":
writeUleb128(w, 0) // number of sets of locals
case "memchr", "memcmp":
writeUleb128(w, 1) // number of sets of locals
@@ -797,9 +836,10 @@
default:
// Normal calling convention: No WebAssembly parameters. First local variable is local SP cache.
hasLocalSP = true
+ hasPC_B = true
numI, numF := countRegisters(s)
- r0 = 1
- f0 = 1 + numI
+ r0 = 2
+ f0 = 2 + numI
numTypes := 1
if numI > 0 {
@@ -826,6 +866,7 @@
// Copy SP from its global variable into a local variable. Accessing a local variable is more efficient.
updateLocalSP(w)
}
+
for p := s.Func.Text; p != nil; p = p.Link {
switch p.As {
case AGet:
@@ -836,10 +877,16 @@
switch {
case reg == REG_SP && hasLocalSP:
w.WriteByte(0x20) // local.get
- writeUleb128(w, 0) // local SP
- case reg >= REG_PC_F && reg <= REG_PAUSE:
+ writeUleb128(w, 1) // local SP
+ case reg >= REG_SP && reg <= REG_PAUSE:
w.WriteByte(0x23) // global.get
- writeUleb128(w, uint64(reg-REG_PC_F))
+ writeUleb128(w, uint64(reg-REG_SP))
+ case reg == REG_PC_B:
+ if !hasPC_B {
+ panic(fmt.Sprintf("PC_B is not used in %s", s.Name))
+ }
+ w.WriteByte(0x20) // local.get (i32)
+ writeUleb128(w, 0) // local PC_B
case reg >= REG_R0 && reg <= REG_R15:
w.WriteByte(0x20) // local.get (i64)
writeUleb128(w, uint64(r0+(reg-REG_R0)))
@@ -857,21 +904,26 @@
}
reg := p.To.Reg
switch {
- case reg >= REG_PC_F && reg <= REG_PAUSE:
+ case reg >= REG_SP && reg <= REG_PAUSE:
if reg == REG_SP && hasLocalSP {
w.WriteByte(0x22) // local.tee
- writeUleb128(w, 0) // local SP
+ writeUleb128(w, 1) // local SP
}
w.WriteByte(0x24) // global.set
- writeUleb128(w, uint64(reg-REG_PC_F))
- case reg >= REG_R0 && reg <= REG_F15:
+ writeUleb128(w, uint64(reg-REG_SP))
+ case reg >= REG_R0 && reg <= REG_PC_B:
if p.Link.As == AGet && p.Link.From.Reg == reg {
w.WriteByte(0x22) // local.tee
p = p.Link
} else {
w.WriteByte(0x21) // local.set
}
- if reg <= REG_R15 {
+ if reg == REG_PC_B {
+ if !hasPC_B {
+ panic(fmt.Sprintf("PC_B is not used in %s", s.Name))
+ }
+ writeUleb128(w, 0) // local PC_B
+ } else if reg <= REG_R15 {
writeUleb128(w, uint64(r0+(reg-REG_R0)))
} else {
writeUleb128(w, uint64(f0+(reg-REG_F0)))
@@ -887,6 +939,12 @@
}
reg := p.To.Reg
switch {
+ case reg == REG_PC_B:
+ if !hasPC_B {
+ panic(fmt.Sprintf("PC_B is not used in %s", s.Name))
+ }
+ w.WriteByte(0x22) // local.tee (i32)
+ writeUleb128(w, 0) // local PC_B
case reg >= REG_R0 && reg <= REG_R15:
w.WriteByte(0x22) // local.tee (i64)
writeUleb128(w, uint64(r0+(reg-REG_R0)))
@@ -1036,10 +1094,10 @@
}
func updateLocalSP(w *bytes.Buffer) {
- w.WriteByte(0x23) // global.get
- writeUleb128(w, uint64(REG_SP-REG_PC_F)) // SP
- w.WriteByte(0x21) // local.set
- writeUleb128(w, 0) // local SP
+ w.WriteByte(0x23) // global.get
+ writeUleb128(w, 0) // global SP
+ w.WriteByte(0x21) // local.set
+ writeUleb128(w, 1) // local SP
}
func align(as obj.As) uint64 {
diff --git a/src/cmd/link/internal/wasm/asm.go b/src/cmd/link/internal/wasm/asm.go
index c80e81e..54b265c 100644
--- a/src/cmd/link/internal/wasm/asm.go
+++ b/src/cmd/link/internal/wasm/asm.go
@@ -102,10 +102,11 @@
}
types := []*wasmFuncType{
- // For normal Go functions the return value is
+ // For normal Go functions, the single parameter is PC_B,
+ // the return value is
// 0 if the function returned normally or
// 1 if the stack needs to be unwound.
- {Results: []byte{I32}},
+ {Params: []byte{I32}, Results: []byte{I32}},
}
// collect host imports (functions that get imported from the WebAssembly host, usually JavaScript)
@@ -320,16 +321,14 @@
sizeOffset := writeSecHeader(ctxt, sectionGlobal)
globalRegs := []byte{
- I32, // 0: PC_F
- I32, // 1: PC_B
- I32, // 2: SP
- I64, // 3: CTXT
- I64, // 4: g
- I64, // 5: RET0
- I64, // 6: RET1
- I64, // 7: RET2
- I64, // 8: RET3
- I32, // 9: PAUSE
+ I32, // 0: SP
+ I64, // 1: CTXT
+ I64, // 2: g
+ I64, // 3: RET0
+ I64, // 4: RET1
+ I64, // 5: RET2
+ I64, // 6: RET3
+ I32, // 7: PAUSE
}
writeUleb128(ctxt.Out, uint64(len(globalRegs))) // number of globals
diff --git a/src/runtime/asm_wasm.s b/src/runtime/asm_wasm.s
index a10c89d..8f3964f 100644
--- a/src/runtime/asm_wasm.s
+++ b/src/runtime/asm_wasm.s
@@ -37,17 +37,12 @@
MOVD gobuf_g(R0), g
MOVD gobuf_sp(R0), SP
+ // Put target PC at -8(SP), wasm_pc_f_loop will pick it up
+ Get SP
+ I32Const $8
+ I32Sub
I64Load gobuf_pc(R0)
- I32WrapI64
- I32Const $16
- I32ShrU
- Set PC_F
-
- I64Load gobuf_pc(R0)
- I64Const $0xFFFF
- I64And
- I32WrapI64
- Set PC_B
+ I64Store $0
MOVD gobuf_ret(R0), RET0
MOVD gobuf_ctxt(R0), CTXT
diff --git a/src/runtime/rt0_js_wasm.s b/src/runtime/rt0_js_wasm.s
index c4efd96..b22c46e 100644
--- a/src/runtime/rt0_js_wasm.s
+++ b/src/runtime/rt0_js_wasm.s
@@ -31,14 +31,9 @@
I64ExtendI32U
I64Store $8
- I32Const $runtime·rt0_go(SB)
- I32Const $16
- I32ShrU
- Set PC_F
-
- I32Const $0
- Set PC_B
-
+ I32Const $0 // entry PC_B
+ Call runtime·rt0_go(SB)
+ Drop
Call wasm_pc_f_loop(SB)
Return
@@ -46,14 +41,9 @@
// wasm_export_resume gets called from JavaScript. It resumes the execution of Go code until it needs to wait for
// an event.
TEXT wasm_export_resume(SB),NOSPLIT,$0
- I32Const $runtime·handleEvent(SB)
- I32Const $16
- I32ShrU
- Set PC_F
-
I32Const $0
- Set PC_B
-
+ Call runtime·handleEvent(SB)
+ Drop
Call wasm_pc_f_loop(SB)
Return
@@ -63,15 +53,30 @@
// The WebAssembly stack may unwind, e.g. when switching goroutines.
// The Go stack on the linear memory is then used to jump to the correct functions
// with this loop, without having to restore the full WebAssembly stack.
-loop:
- Loop
- Get PC_F
- CallIndirect $0
- Drop
+// It is expected to have a pending call before entering the loop, so check PAUSE first.
+ Get PAUSE
+ I32Eqz
+ If
+ loop:
+ Loop
+ // Get PC_B & PC_F from -8(SP)
+ Get SP
+ I32Const $8
+ I32Sub
+ I32Load16U $0 // PC_B
- Get PAUSE
- I32Eqz
- BrIf loop
+ Get SP
+ I32Const $8
+ I32Sub
+ I32Load16U $2 // PC_F
+
+ CallIndirect $0
+ Drop
+
+ Get PAUSE
+ I32Eqz
+ BrIf loop
+ End
End
I32Const $0
@@ -91,6 +96,7 @@
RETUNWIND
TEXT runtime·exit(SB), NOSPLIT, $0-4
+ I32Const $0
Call runtime·wasmExit(SB)
Drop
I32Const $1
