04d12bf2ba
A switch statement is not normally emitted by the compiler package, but LLVM function passes may convert a series of if/else pairs to a switch statement. A future change will run function passes in the package compile phase, so the interp package (which is also run after all modules are merged together) will need to deal with these new switch statements.
419 строки
14 КиБ
Go
419 строки
14 КиБ
Go
package interp
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// This file compiles the LLVM IR to a form that's easy to efficiently
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// interpret.
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import (
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"strings"
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"tinygo.org/x/go-llvm"
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)
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// A function is a compiled LLVM function, which means that interpreting it
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// avoids most CGo calls necessary. This is done in a separate step so the
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// result can be cached.
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// Functions are in SSA form, just like the LLVM version if it. The first block
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// (blocks[0]) is the entry block.
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type function struct {
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llvmFn llvm.Value
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name string // precalculated llvmFn.Name()
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params []llvm.Value // precalculated llvmFn.Params()
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blocks []*basicBlock
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locals map[llvm.Value]int
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}
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// basicBlock represents a LLVM basic block and contains a slice of
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// instructions. The last instruction must be a terminator instruction.
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type basicBlock struct {
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instructions []instruction
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}
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// instruction is a precompiled LLVM IR instruction. The operands can be either
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// an already known value (such as literalValue or pointerValue) but can also be
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// the special localValue, which means that the value is a function parameter or
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// is produced by another instruction in the function. In that case, the
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// interpreter will replace the operand with that local value.
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type instruction struct {
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opcode llvm.Opcode
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localIndex int
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operands []value
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llvmInst llvm.Value
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name string
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}
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// String returns a nice human-readable version of this instruction.
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func (inst *instruction) String() string {
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operands := make([]string, len(inst.operands))
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for i, op := range inst.operands {
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operands[i] = op.String()
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}
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name := instructionNameMap[inst.opcode]
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if name == "" {
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name = "<unknown op>"
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}
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return name + " " + strings.Join(operands, " ")
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}
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// compileFunction compiles a given LLVM function to an easier to interpret
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// version of the function. As far as possible, all operands are preprocessed so
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// that the interpreter doesn't have to call into LLVM.
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func (r *runner) compileFunction(llvmFn llvm.Value) *function {
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fn := &function{
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llvmFn: llvmFn,
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name: llvmFn.Name(),
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params: llvmFn.Params(),
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locals: make(map[llvm.Value]int),
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}
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if llvmFn.IsDeclaration() {
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// Nothing to do.
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return fn
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}
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for i, param := range fn.params {
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fn.locals[param] = i
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}
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// Make a map of all the blocks, to quickly find the block number for a
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// given branch instruction.
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blockIndices := make(map[llvm.Value]int)
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for llvmBB := llvmFn.FirstBasicBlock(); !llvmBB.IsNil(); llvmBB = llvm.NextBasicBlock(llvmBB) {
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index := len(blockIndices)
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blockIndices[llvmBB.AsValue()] = index
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}
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// Compile every block.
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for llvmBB := llvmFn.FirstBasicBlock(); !llvmBB.IsNil(); llvmBB = llvm.NextBasicBlock(llvmBB) {
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bb := &basicBlock{}
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fn.blocks = append(fn.blocks, bb)
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// Compile every instruction in the block.
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for llvmInst := llvmBB.FirstInstruction(); !llvmInst.IsNil(); llvmInst = llvm.NextInstruction(llvmInst) {
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// Create instruction skeleton.
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opcode := llvmInst.InstructionOpcode()
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inst := instruction{
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opcode: opcode,
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localIndex: len(fn.locals),
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llvmInst: llvmInst,
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}
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fn.locals[llvmInst] = len(fn.locals)
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// Add operands specific for this instruction.
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switch opcode {
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case llvm.Ret:
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// Return instruction, which can either be a `ret void` (no
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// return value) or return a value.
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numOperands := llvmInst.OperandsCount()
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if numOperands != 0 {
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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}
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}
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case llvm.Br:
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// Branch instruction. Can be either a conditional branch (with
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// 3 operands) or unconditional branch (with just one basic
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// block operand).
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numOperands := llvmInst.OperandsCount()
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switch numOperands {
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case 3:
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// Conditional jump to one of two blocks. Comparable to an
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// if/else in procedural languages.
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thenBB := llvmInst.Operand(2)
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elseBB := llvmInst.Operand(1)
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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literalValue{uint32(blockIndices[thenBB])},
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literalValue{uint32(blockIndices[elseBB])},
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}
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case 1:
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// Unconditional jump to a target basic block. Comparable to
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// a jump in C and Go.
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jumpBB := llvmInst.Operand(0)
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inst.operands = []value{
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literalValue{uint32(blockIndices[jumpBB])},
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}
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default:
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panic("unknown number of operands")
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}
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case llvm.Switch:
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// A switch is an array of (value, label) pairs, of which the
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// first one indicates the to-switch value and the default
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// label.
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numOperands := llvmInst.OperandsCount()
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for i := 0; i < numOperands; i += 2 {
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inst.operands = append(inst.operands, r.getValue(llvmInst.Operand(i)))
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inst.operands = append(inst.operands, literalValue{uint32(blockIndices[llvmInst.Operand(i+1)])})
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}
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case llvm.PHI:
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inst.name = llvmInst.Name()
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incomingCount := inst.llvmInst.IncomingCount()
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for i := 0; i < incomingCount; i++ {
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incomingBB := inst.llvmInst.IncomingBlock(i)
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incomingValue := inst.llvmInst.IncomingValue(i)
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inst.operands = append(inst.operands,
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literalValue{uint32(blockIndices[incomingBB.AsValue()])},
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r.getValue(incomingValue),
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)
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}
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case llvm.Select:
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// Select is a special instruction that is much like a ternary
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// operator. It produces operand 1 or 2 based on the boolean
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// that is operand 0.
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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r.getValue(llvmInst.Operand(1)),
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r.getValue(llvmInst.Operand(2)),
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}
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case llvm.Call:
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// Call is a regular function call but could also be a runtime
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// intrinsic. Some runtime intrinsics are treated specially by
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// the interpreter, such as runtime.alloc. We don't
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// differentiate between them here because these calls may also
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// need to be run at runtime, in which case they should all be
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// created in the same way.
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llvmCalledValue := llvmInst.CalledValue()
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if !llvmCalledValue.IsAFunction().IsNil() {
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name := llvmCalledValue.Name()
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if name == "llvm.dbg.value" || strings.HasPrefix(name, "llvm.lifetime.") {
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// These intrinsics should not be interpreted, they are not
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// relevant to the execution of this function.
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continue
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}
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}
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inst.name = llvmInst.Name()
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numOperands := llvmInst.OperandsCount()
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inst.operands = append(inst.operands, r.getValue(llvmCalledValue))
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for i := 0; i < numOperands-1; i++ {
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inst.operands = append(inst.operands, r.getValue(llvmInst.Operand(i)))
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}
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case llvm.Load:
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// Load instruction. The interpreter will load from the
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// appropriate memory view.
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// Also provide the memory size to be loaded, which is necessary
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// with a lack of type information.
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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literalValue{r.targetData.TypeAllocSize(llvmInst.Type())},
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}
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case llvm.Store:
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// Store instruction. The interpreter will create a new object
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// in the memory view of the function invocation and store to
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// that, to make it possible to roll back this store.
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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r.getValue(llvmInst.Operand(1)),
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}
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case llvm.Alloca:
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// Alloca allocates stack space for local variables.
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numElements := r.getValue(inst.llvmInst.Operand(0)).(literalValue).value.(uint32)
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elementSize := r.targetData.TypeAllocSize(inst.llvmInst.Type().ElementType())
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inst.operands = []value{
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literalValue{elementSize * uint64(numElements)},
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}
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case llvm.GetElementPtr:
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// GetElementPtr does pointer arithmetic.
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inst.name = llvmInst.Name()
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ptr := llvmInst.Operand(0)
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n := llvmInst.OperandsCount()
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elementType := ptr.Type().ElementType()
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// gep: [source ptr, dest value size, pairs of indices...]
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inst.operands = []value{
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r.getValue(ptr),
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literalValue{r.targetData.TypeAllocSize(llvmInst.Type().ElementType())},
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r.getValue(llvmInst.Operand(1)),
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literalValue{r.targetData.TypeAllocSize(elementType)},
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}
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for i := 2; i < n; i++ {
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operand := r.getValue(llvmInst.Operand(i))
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if elementType.TypeKind() == llvm.StructTypeKind {
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index := operand.(literalValue).value.(uint32)
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elementOffset := r.targetData.ElementOffset(elementType, int(index))
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// Encode operands in a special way. The elementOffset
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// is just the offset in bytes. The elementSize is a
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// negative number (when cast to a int64) by flipping
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// all the bits. This allows the interpreter to detect
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// this is a struct field and that it should not
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// multiply it with the elementOffset to get the offset.
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// It is important for the interpreter to know the
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// struct field index for when the GEP must be done at
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// runtime.
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inst.operands = append(inst.operands, literalValue{elementOffset}, literalValue{^uint64(index)})
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elementType = elementType.StructElementTypes()[index]
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} else {
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elementType = elementType.ElementType()
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elementSize := r.targetData.TypeAllocSize(elementType)
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elementSizeOperand := literalValue{elementSize}
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// Add operand * elementSizeOperand bytes to the pointer.
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inst.operands = append(inst.operands, operand, elementSizeOperand)
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}
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}
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case llvm.BitCast, llvm.IntToPtr, llvm.PtrToInt:
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// Bitcasts are ususally used to cast a pointer from one type to
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// another leaving the pointer itself intact.
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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}
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case llvm.ExtractValue:
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inst.name = llvmInst.Name()
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agg := llvmInst.Operand(0)
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var offset uint64
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indexingType := agg.Type()
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for _, index := range inst.llvmInst.Indices() {
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switch indexingType.TypeKind() {
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case llvm.StructTypeKind:
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offset += r.targetData.ElementOffset(indexingType, int(index))
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indexingType = indexingType.StructElementTypes()[index]
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default: // ArrayTypeKind
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indexingType = indexingType.ElementType()
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elementSize := r.targetData.TypeAllocSize(indexingType)
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offset += elementSize * uint64(index)
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}
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}
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size := r.targetData.TypeAllocSize(inst.llvmInst.Type())
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// extractvalue [agg, byteOffset, byteSize]
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inst.operands = []value{
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r.getValue(agg),
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literalValue{offset},
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literalValue{size},
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}
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case llvm.InsertValue:
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inst.name = llvmInst.Name()
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agg := llvmInst.Operand(0)
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var offset uint64
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indexingType := agg.Type()
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for _, index := range inst.llvmInst.Indices() {
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switch indexingType.TypeKind() {
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case llvm.StructTypeKind:
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offset += r.targetData.ElementOffset(indexingType, int(index))
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indexingType = indexingType.StructElementTypes()[index]
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default: // ArrayTypeKind
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indexingType = indexingType.ElementType()
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elementSize := r.targetData.TypeAllocSize(indexingType)
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offset += elementSize * uint64(index)
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}
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}
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// insertvalue [agg, elt, byteOffset]
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inst.operands = []value{
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r.getValue(agg),
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r.getValue(llvmInst.Operand(1)),
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literalValue{offset},
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}
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case llvm.ICmp:
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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r.getValue(llvmInst.Operand(1)),
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literalValue{uint8(llvmInst.IntPredicate())},
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}
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case llvm.FCmp:
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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r.getValue(llvmInst.Operand(1)),
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literalValue{uint8(llvmInst.FloatPredicate())},
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}
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case llvm.Add, llvm.Sub, llvm.Mul, llvm.UDiv, llvm.SDiv, llvm.URem, llvm.SRem, llvm.Shl, llvm.LShr, llvm.AShr, llvm.And, llvm.Or, llvm.Xor:
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// Integer binary operations.
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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r.getValue(llvmInst.Operand(1)),
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}
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case llvm.SExt, llvm.ZExt, llvm.Trunc:
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// Extend or shrink an integer size.
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// No sign extension going on so easy to do.
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// zext: [value, bitwidth]
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// trunc: [value, bitwidth]
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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literalValue{uint64(llvmInst.Type().IntTypeWidth())},
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}
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case llvm.SIToFP, llvm.UIToFP:
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// Convert an integer to a floating point instruction.
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// opcode: [value, bitwidth]
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inst.name = llvmInst.Name()
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inst.operands = []value{
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r.getValue(llvmInst.Operand(0)),
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literalValue{uint64(r.targetData.TypeAllocSize(llvmInst.Type()) * 8)},
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}
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default:
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// Unknown instruction, which is already set in inst.opcode so
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// is detectable.
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// This error is handled when actually trying to interpret this
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// instruction (to not trigger on code that won't be executed).
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}
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bb.instructions = append(bb.instructions, inst)
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}
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}
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return fn
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}
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// instructionNameMap maps from instruction opcodes to instruction names. This
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// can be useful for debug logging.
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var instructionNameMap = [...]string{
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llvm.Ret: "ret",
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llvm.Br: "br",
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llvm.Switch: "switch",
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llvm.IndirectBr: "indirectbr",
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llvm.Invoke: "invoke",
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llvm.Unreachable: "unreachable",
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// Standard Binary Operators
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llvm.Add: "add",
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llvm.FAdd: "fadd",
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llvm.Sub: "sub",
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llvm.FSub: "fsub",
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llvm.Mul: "mul",
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llvm.FMul: "fmul",
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llvm.UDiv: "udiv",
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llvm.SDiv: "sdiv",
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llvm.FDiv: "fdiv",
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llvm.URem: "urem",
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llvm.SRem: "srem",
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llvm.FRem: "frem",
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// Logical Operators
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llvm.Shl: "shl",
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llvm.LShr: "lshr",
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llvm.AShr: "ashr",
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llvm.And: "and",
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llvm.Or: "or",
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llvm.Xor: "xor",
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// Memory Operators
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llvm.Alloca: "alloca",
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llvm.Load: "load",
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llvm.Store: "store",
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llvm.GetElementPtr: "getelementptr",
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// Cast Operators
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llvm.Trunc: "trunc",
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llvm.ZExt: "zext",
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llvm.SExt: "sext",
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llvm.FPToUI: "fptoui",
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llvm.FPToSI: "fptosi",
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llvm.UIToFP: "uitofp",
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llvm.SIToFP: "sitofp",
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llvm.FPTrunc: "fptrunc",
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llvm.FPExt: "fpext",
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llvm.PtrToInt: "ptrtoint",
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llvm.IntToPtr: "inttoptr",
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llvm.BitCast: "bitcast",
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// Other Operators
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llvm.ICmp: "icmp",
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llvm.FCmp: "fcmp",
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llvm.PHI: "phi",
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llvm.Call: "call",
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llvm.Select: "select",
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llvm.VAArg: "vaarg",
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llvm.ExtractElement: "extractelement",
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llvm.InsertElement: "insertelement",
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llvm.ShuffleVector: "shufflevector",
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llvm.ExtractValue: "extractvalue",
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llvm.InsertValue: "insertvalue",
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}
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