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236 lines
8.8 KiB
236 lines
8.8 KiB
package compiler
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// This file implements the syscall.Syscall and syscall.Syscall6 instructions as
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// compiler builtins.
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import (
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"strconv"
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"golang.org/x/tools/go/ssa"
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"tinygo.org/x/go-llvm"
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)
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// createRawSyscall creates a system call with the provided system call number
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// and returns the result as a single integer (the system call result). The
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// result is not further interpreted.
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func (b *builder) createRawSyscall(call *ssa.CallCommon) (llvm.Value, error) {
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num := b.getValue(call.Args[0], getPos(call))
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switch {
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case b.GOARCH == "amd64" && b.GOOS == "linux":
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// Sources:
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// https://stackoverflow.com/a/2538212
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// https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux#syscall
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args := []llvm.Value{num}
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argTypes := []llvm.Type{b.uintptrType}
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// Constraints will look something like:
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// "={rax},0,{rdi},{rsi},{rdx},{r10},{r8},{r9},~{rcx},~{r11}"
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constraints := "={rax},0"
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for i, arg := range call.Args[1:] {
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constraints += "," + [...]string{
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"{rdi}",
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"{rsi}",
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"{rdx}",
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"{r10}",
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"{r8}",
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"{r9}",
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"{r11}",
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"{r12}",
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"{r13}",
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}[i]
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llvmValue := b.getValue(arg, getPos(call))
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args = append(args, llvmValue)
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argTypes = append(argTypes, llvmValue.Type())
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}
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constraints += ",~{rcx},~{r11}"
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fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
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target := llvm.InlineAsm(fnType, "syscall", constraints, true, false, llvm.InlineAsmDialectIntel, false)
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return b.CreateCall(fnType, target, args, ""), nil
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case b.GOARCH == "386" && b.GOOS == "linux":
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// Sources:
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// syscall(2) man page
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// https://stackoverflow.com/a/2538212
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// https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux#int_0x80
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args := []llvm.Value{num}
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argTypes := []llvm.Type{b.uintptrType}
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// Constraints will look something like:
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// "={eax},0,{ebx},{ecx},{edx},{esi},{edi},{ebp}"
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constraints := "={eax},0"
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for i, arg := range call.Args[1:] {
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constraints += "," + [...]string{
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"{ebx}",
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"{ecx}",
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"{edx}",
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"{esi}",
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"{edi}",
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"{ebp}",
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}[i]
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llvmValue := b.getValue(arg, getPos(call))
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args = append(args, llvmValue)
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argTypes = append(argTypes, llvmValue.Type())
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}
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fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
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target := llvm.InlineAsm(fnType, "int 0x80", constraints, true, false, llvm.InlineAsmDialectIntel, false)
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return b.CreateCall(fnType, target, args, ""), nil
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case b.GOARCH == "arm" && b.GOOS == "linux":
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// Implement the EABI system call convention for Linux.
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// Source: syscall(2) man page.
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args := []llvm.Value{}
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argTypes := []llvm.Type{}
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// Constraints will look something like:
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// ={r0},0,{r1},{r2},{r7},~{r3}
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constraints := "={r0}"
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for i, arg := range call.Args[1:] {
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constraints += "," + [...]string{
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"0", // tie to output
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"{r1}",
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"{r2}",
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"{r3}",
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"{r4}",
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"{r5}",
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"{r6}",
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}[i]
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llvmValue := b.getValue(arg, getPos(call))
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args = append(args, llvmValue)
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argTypes = append(argTypes, llvmValue.Type())
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}
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args = append(args, num)
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argTypes = append(argTypes, b.uintptrType)
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constraints += ",{r7}" // syscall number
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for i := len(call.Args) - 1; i < 4; i++ {
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// r0-r3 get clobbered after the syscall returns
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constraints += ",~{r" + strconv.Itoa(i) + "}"
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}
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fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
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target := llvm.InlineAsm(fnType, "svc #0", constraints, true, false, 0, false)
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return b.CreateCall(fnType, target, args, ""), nil
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case b.GOARCH == "arm64" && b.GOOS == "linux":
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// Source: syscall(2) man page.
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args := []llvm.Value{}
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argTypes := []llvm.Type{}
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// Constraints will look something like:
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// ={x0},0,{x1},{x2},{x8},~{x3},~{x4},~{x5},~{x6},~{x7},~{x16},~{x17}
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constraints := "={x0}"
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for i, arg := range call.Args[1:] {
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constraints += "," + [...]string{
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"0", // tie to output
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"{x1}",
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"{x2}",
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"{x3}",
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"{x4}",
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"{x5}",
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}[i]
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llvmValue := b.getValue(arg, getPos(call))
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args = append(args, llvmValue)
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argTypes = append(argTypes, llvmValue.Type())
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}
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args = append(args, num)
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argTypes = append(argTypes, b.uintptrType)
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constraints += ",{x8}" // syscall number
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for i := len(call.Args) - 1; i < 8; i++ {
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// x0-x7 may get clobbered during the syscall following the aarch64
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// calling convention.
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constraints += ",~{x" + strconv.Itoa(i) + "}"
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}
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constraints += ",~{x16},~{x17}" // scratch registers
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fnType := llvm.FunctionType(b.uintptrType, argTypes, false)
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target := llvm.InlineAsm(fnType, "svc #0", constraints, true, false, 0, false)
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return b.CreateCall(fnType, target, args, ""), nil
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default:
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return llvm.Value{}, b.makeError(call.Pos(), "unknown GOOS/GOARCH for syscall: "+b.GOOS+"/"+b.GOARCH)
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}
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}
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// createSyscall emits instructions for the syscall.Syscall* family of
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// functions, depending on the target OS/arch.
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func (b *builder) createSyscall(call *ssa.CallCommon) (llvm.Value, error) {
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switch b.GOOS {
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case "linux":
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syscallResult, err := b.createRawSyscall(call)
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if err != nil {
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return syscallResult, err
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}
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// Return values: r0, r1 uintptr, err Errno
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// Pseudocode:
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// var err uintptr
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// if syscallResult < 0 && syscallResult > -4096 {
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// err = -syscallResult
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// }
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// return syscallResult, 0, err
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zero := llvm.ConstInt(b.uintptrType, 0, false)
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inrange1 := b.CreateICmp(llvm.IntSLT, syscallResult, llvm.ConstInt(b.uintptrType, 0, false), "")
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inrange2 := b.CreateICmp(llvm.IntSGT, syscallResult, llvm.ConstInt(b.uintptrType, 0xfffffffffffff000, true), "") // -4096
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hasError := b.CreateAnd(inrange1, inrange2, "")
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errResult := b.CreateSelect(hasError, b.CreateSub(zero, syscallResult, ""), zero, "syscallError")
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retval := llvm.Undef(b.ctx.StructType([]llvm.Type{b.uintptrType, b.uintptrType, b.uintptrType}, false))
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retval = b.CreateInsertValue(retval, syscallResult, 0, "")
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retval = b.CreateInsertValue(retval, zero, 1, "")
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retval = b.CreateInsertValue(retval, errResult, 2, "")
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return retval, nil
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case "windows":
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// On Windows, syscall.Syscall* is basically just a function pointer
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// call. This is complicated in gc because of stack switching and the
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// different ABI, but easy in TinyGo: just call the function pointer.
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// The signature looks like this:
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// func Syscall(trap, nargs, a1, a2, a3 uintptr) (r1, r2 uintptr, err Errno)
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// Prepare input values.
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var paramTypes []llvm.Type
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var params []llvm.Value
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for _, val := range call.Args[2:] {
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param := b.getValue(val, getPos(call))
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params = append(params, param)
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paramTypes = append(paramTypes, param.Type())
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}
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llvmType := llvm.FunctionType(b.uintptrType, paramTypes, false)
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fn := b.getValue(call.Args[0], getPos(call))
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fnPtr := b.CreateIntToPtr(fn, llvm.PointerType(llvmType, 0), "")
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// Prepare some functions that will be called later.
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setLastError := b.mod.NamedFunction("SetLastError")
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if setLastError.IsNil() {
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llvmType := llvm.FunctionType(b.ctx.VoidType(), []llvm.Type{b.ctx.Int32Type()}, false)
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setLastError = llvm.AddFunction(b.mod, "SetLastError", llvmType)
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}
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getLastError := b.mod.NamedFunction("GetLastError")
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if getLastError.IsNil() {
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llvmType := llvm.FunctionType(b.ctx.Int32Type(), nil, false)
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getLastError = llvm.AddFunction(b.mod, "GetLastError", llvmType)
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}
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// Now do the actual call. Pseudocode:
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// SetLastError(0)
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// r1 = trap(a1, a2, a3, ...)
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// err = uintptr(GetLastError())
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// return r1, 0, err
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// Note that SetLastError/GetLastError could be replaced with direct
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// access to the thread control block, which is probably smaller and
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// faster. The Go runtime does this in assembly.
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b.CreateCall(setLastError.GlobalValueType(), setLastError, []llvm.Value{llvm.ConstNull(b.ctx.Int32Type())}, "")
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syscallResult := b.CreateCall(llvmType, fnPtr, params, "")
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errResult := b.CreateCall(getLastError.GlobalValueType(), getLastError, nil, "err")
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if b.uintptrType != b.ctx.Int32Type() {
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errResult = b.CreateZExt(errResult, b.uintptrType, "err.uintptr")
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}
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// Return r1, 0, err
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retval := llvm.ConstNull(b.ctx.StructType([]llvm.Type{b.uintptrType, b.uintptrType, b.uintptrType}, false))
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retval = b.CreateInsertValue(retval, syscallResult, 0, "")
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retval = b.CreateInsertValue(retval, errResult, 2, "")
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return retval, nil
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default:
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return llvm.Value{}, b.makeError(call.Pos(), "unknown GOOS/GOARCH for syscall: "+b.GOOS+"/"+b.GOARCH)
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}
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}
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// createRawSyscallNoError emits instructions for the Linux-specific
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// syscall.rawSyscallNoError function.
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func (b *builder) createRawSyscallNoError(call *ssa.CallCommon) (llvm.Value, error) {
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syscallResult, err := b.createRawSyscall(call)
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if err != nil {
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return syscallResult, err
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}
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retval := llvm.ConstNull(b.ctx.StructType([]llvm.Type{b.uintptrType, b.uintptrType}, false))
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retval = b.CreateInsertValue(retval, syscallResult, 0, "")
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retval = b.CreateInsertValue(retval, llvm.ConstInt(b.uintptrType, 0, false), 1, "")
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return retval, nil
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}
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