support WASI target (#1373)

* initial commit for WASI support

* merge "time" package with wasi build tag
* override syscall package with wasi build tag
* create runtime_wasm_{js,wasi}.go files
* create syscall_wasi.go file
* create time/zoneinfo_wasi.go file as the replacement of zoneinfo_js.go
* add targets/wasi.json target

* set visbility hidden for runtime extern variables

Accodring to the WASI docs (https://github.com/WebAssembly/WASI/blob/master/design/application-abi.md#current-unstable-abi),
none of exports of WASI executable(Command) should no be accessed.

v0.19.0 of bytecodealliance/wasmetime, which is often refered to as the reference implementation of WASI,
does not accept any exports except functions and the only limited variables like "table", "memory".

* merge syscall_{baremetal,wasi}.go

* fix js target build

* mv wasi functions to syscall/wasi && implement sleepTicks

* WASI: set visibility hidden for globals variables

* mv back syscall/wasi/* to runtime package

* WASI: add test

* unexport wasi types

* WASI test: fix wasmtime path

* stop changing visibility of runtime.alloc

* use GOOS=linux, GOARCH=arm for wasi target

Signed-off-by: mathetake <takeshi@tetrate.io>

* WASI: fix build tags for os/runtime packages

Signed-off-by: mathetake <takeshi@tetrate.io>

* run WASI test only on Linux

Signed-off-by: mathetake <takeshi@tetrate.io>

* set InternalLinkage instead of changing visibility

Signed-off-by: mathetake <takeshi@tetrate.io>

transform/gc.go

@@ -19,6 +19,7 @@ func MakeGCStackSlots(mod llvm.Module) bool {
 		}
 		stackChainStart := mod.NamedGlobal("runtime.stackChainStart")
 		if !stackChainStart.IsNil() {
+			stackChainStart.SetLinkage(llvm.InternalLinkage)
 			stackChainStart.SetInitializer(llvm.ConstNull(stackChainStart.Type().ElementType()))
 			stackChainStart.SetGlobalConstant(true)
 		}
@@ -94,6 +95,7 @@ func MakeGCStackSlots(mod llvm.Module) bool {
 		}
 		return false
 	}
+	stackChainStart.SetLinkage(llvm.InternalLinkage)
 	stackChainStartType := stackChainStart.Type().ElementType()
 	stackChainStart.SetInitializer(llvm.ConstNull(stackChainStartType))
 
@@ -333,11 +335,13 @@ func AddGlobalsBitmap(mod llvm.Module) bool {
 	// Update trackedGlobalsStart, which points to the globals bundle.
 	trackedGlobalsStart := llvm.ConstPtrToInt(globalsBundle, uintptrType)
 	mod.NamedGlobal("runtime.trackedGlobalsStart").SetInitializer(trackedGlobalsStart)
+	mod.NamedGlobal("runtime.trackedGlobalsStart").SetLinkage(llvm.InternalLinkage)
 
 	// Update trackedGlobalsLength, which contains the length (in words) of the
 	// globals bundle.
 	alignment := targetData.PrefTypeAlignment(llvm.PointerType(ctx.Int8Type(), 0))
 	trackedGlobalsLength := llvm.ConstInt(uintptrType, targetData.TypeAllocSize(globalsBundleType)/uint64(alignment), false)
+	mod.NamedGlobal("runtime.trackedGlobalsLength").SetLinkage(llvm.InternalLinkage)
 	mod.NamedGlobal("runtime.trackedGlobalsLength").SetInitializer(trackedGlobalsLength)
 
 	// Create a bitmap (a new global) that stores for each word in the globals
@@ -357,6 +361,7 @@ func AddGlobalsBitmap(mod llvm.Module) bool {
 	bitmapOld.ReplaceAllUsesWith(llvm.ConstBitCast(bitmapNew, bitmapOld.Type()))
 	bitmapNew.SetInitializer(bitmapArray)
 	bitmapNew.SetName("runtime.trackedGlobalsBitmap")
+	bitmapNew.SetLinkage(llvm.InternalLinkage)
 
 	return true // the IR was changed
 }

transform/testdata/gc-globals.out.ll

@@ -7,11 +7,11 @@ target triple = "wasm32-unknown-unknown-wasm"
 @globalInt = global i32 5
 @constString = constant %runtime._string zeroinitializer
 @constInterface = constant %runtime._interface zeroinitializer
-@runtime.trackedGlobalsLength = global i32 4
+@runtime.trackedGlobalsLength = internal global i32 4
 @runtime.trackedGlobalsBitmap = external global [0 x i8]
-@runtime.trackedGlobalsStart = global i32 ptrtoint ({ %runtime._string, %runtime._interface }* @tinygo.trackedGlobals to i32)
+@runtime.trackedGlobalsStart = internal global i32 ptrtoint ({ %runtime._string, %runtime._interface }* @tinygo.trackedGlobals to i32)
 @tinygo.trackedGlobals = internal unnamed_addr global { %runtime._string, %runtime._interface } zeroinitializer
-@runtime.trackedGlobalsBitmap.1 = global [1 x i8] c"\09"
+@runtime.trackedGlobalsBitmap.1 = internal global [1 x i8] c"\09"
 
 define void @main() {
   %1 = load i32, i32* @globalInt

transform/testdata/gc-stackslots.out.ll

@@ -3,7 +3,7 @@ target triple = "wasm32-unknown-unknown-wasm"
 
 %runtime.stackChainObject = type { %runtime.stackChainObject*, i32 }
 
-@runtime.stackChainStart = global %runtime.stackChainObject* null
+@runtime.stackChainStart = internal global %runtime.stackChainObject* null
 @someGlobal = global i8 3
 
 declare void @runtime.trackPointer(i8* nocapture readonly)