From 6c631ae227cb6f15d5b0b8cc39c1715b8f4e9187 Mon Sep 17 00:00:00 2001 From: Denys Smirnov Date: Fri, 19 Oct 2018 19:04:29 +0000 Subject: [PATCH] cmd/compile: in wasm, allocate approximately right number of locals for functions Currently, WASM binary writer requests 16 int registers (locals) and 16 float registers for every function regardless of how many locals the function uses. This change counts the number of used registers and requests a number of locals matching the highest register index. The change has no effect on performance and neglectable binary size improvement, but it makes WASM code more readable and easy to analyze. Change-Id: Ic1079623c0d632b215c68482db909fa440892700 GitHub-Last-Rev: 184634fa918aff74e280904dc2efafcc80735a8b GitHub-Pull-Request: golang/go#28116 Reviewed-on: https://go-review.googlesource.com/c/140999 Reviewed-by: Richard Musiol Run-TryBot: Richard Musiol TryBot-Result: Gobot Gobot --- src/cmd/internal/obj/wasm/wasmobj.go | 73 ++++++++++++++++++++++++---- 1 file changed, 63 insertions(+), 10 deletions(-) diff --git a/src/cmd/internal/obj/wasm/wasmobj.go b/src/cmd/internal/obj/wasm/wasmobj.go index 8498b40724..b1eae2882b 100644 --- a/src/cmd/internal/obj/wasm/wasmobj.go +++ b/src/cmd/internal/obj/wasm/wasmobj.go @@ -705,11 +705,42 @@ func regAddr(reg int16) obj.Addr { return obj.Addr{Type: obj.TYPE_REG, Reg: reg} } +// countRegisters returns the number of integer and float registers used by s. +// It does so by looking for the maximum I* and R* registers. +func countRegisters(s *obj.LSym) (numI, numF int16) { + for p := s.Func.Text; p != nil; p = p.Link { + var reg int16 + switch p.As { + case AGet: + reg = p.From.Reg + case ASet: + reg = p.To.Reg + case ATee: + reg = p.To.Reg + default: + continue + } + if reg >= REG_R0 && reg <= REG_R15 { + if n := reg - REG_R0 + 1; numI < n { + numI = n + } + } else if reg >= REG_F0 && reg <= REG_F15 { + if n := reg - REG_F0 + 1; numF < n { + numF = n + } + } + } + return +} + func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { w := new(bytes.Buffer) + numI, numF := countRegisters(s) + // Function starts with declaration of locals: numbers and types. switch s.Name { + // memchr and memcmp don't use the normal Go calling convention and need i32 variables. case "memchr": writeUleb128(w, 1) // number of sets of locals writeUleb128(w, 3) // number of locals @@ -719,11 +750,23 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { writeUleb128(w, 2) // number of locals w.WriteByte(0x7F) // i32 default: - writeUleb128(w, 2) // number of sets of locals - writeUleb128(w, 16) // number of locals - w.WriteByte(0x7E) // i64 - writeUleb128(w, 16) // number of locals - w.WriteByte(0x7C) // f64 + numTypes := 0 + if numI > 0 { + numTypes++ + } + if numF > 0 { + numTypes++ + } + + writeUleb128(w, uint64(numTypes)) + if numI > 0 { + writeUleb128(w, uint64(numI)) // number of locals + w.WriteByte(0x7E) // i64 + } + if numF > 0 { + writeUleb128(w, uint64(numF)) // number of locals + w.WriteByte(0x7C) // f64 + } } for p := s.Func.Text; p != nil; p = p.Link { @@ -737,9 +780,12 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { case reg >= REG_PC_F && reg <= REG_RUN: w.WriteByte(0x23) // get_global writeUleb128(w, uint64(reg-REG_PC_F)) - case reg >= REG_R0 && reg <= REG_F15: - w.WriteByte(0x20) // get_local + case reg >= REG_R0 && reg <= REG_R15: + w.WriteByte(0x20) // get_local (i64) writeUleb128(w, uint64(reg-REG_R0)) + case reg >= REG_F0 && reg <= REG_F15: + w.WriteByte(0x20) // get_local (f64) + writeUleb128(w, uint64(numI+(reg-REG_F0))) default: panic("bad Get: invalid register") } @@ -761,7 +807,11 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { } else { w.WriteByte(0x21) // set_local } - writeUleb128(w, uint64(reg-REG_R0)) + if reg <= REG_R15 { + writeUleb128(w, uint64(reg-REG_R0)) + } else { + writeUleb128(w, uint64(numI+(reg-REG_F0))) + } default: panic("bad Set: invalid register") } @@ -773,9 +823,12 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) { } reg := p.To.Reg switch { - case reg >= REG_R0 && reg <= REG_F15: - w.WriteByte(0x22) // tee_local + case reg >= REG_R0 && reg <= REG_R15: + w.WriteByte(0x22) // tee_local (i64) writeUleb128(w, uint64(reg-REG_R0)) + case reg >= REG_F0 && reg <= REG_F15: + w.WriteByte(0x22) // tee_local (f64) + writeUleb128(w, uint64(numI+(reg-REG_F0))) default: panic("bad Tee: invalid register") } -- 2.50.0