diff options
Diffstat (limited to 'vendor/github.com/tetratelabs/wazero/internal/engine/wazevo/frontend/frontend.go')
| -rw-r--r-- | vendor/github.com/tetratelabs/wazero/internal/engine/wazevo/frontend/frontend.go | 594 |
1 files changed, 594 insertions, 0 deletions
diff --git a/vendor/github.com/tetratelabs/wazero/internal/engine/wazevo/frontend/frontend.go b/vendor/github.com/tetratelabs/wazero/internal/engine/wazevo/frontend/frontend.go new file mode 100644 index 000000000..873a35a55 --- /dev/null +++ b/vendor/github.com/tetratelabs/wazero/internal/engine/wazevo/frontend/frontend.go @@ -0,0 +1,594 @@ +// Package frontend implements the translation of WebAssembly to SSA IR using the ssa package. +package frontend + +import ( + "bytes" + "math" + + "github.com/tetratelabs/wazero/internal/engine/wazevo/ssa" + "github.com/tetratelabs/wazero/internal/engine/wazevo/wazevoapi" + "github.com/tetratelabs/wazero/internal/wasm" +) + +// Compiler is in charge of lowering Wasm to SSA IR, and does the optimization +// on top of it in architecture-independent way. +type Compiler struct { + // Per-module data that is used across all functions. + + m *wasm.Module + offset *wazevoapi.ModuleContextOffsetData + // ssaBuilder is a ssa.Builder used by this frontend. + ssaBuilder ssa.Builder + signatures map[*wasm.FunctionType]*ssa.Signature + listenerSignatures map[*wasm.FunctionType][2]*ssa.Signature + memoryGrowSig ssa.Signature + memoryWait32Sig ssa.Signature + memoryWait64Sig ssa.Signature + memoryNotifySig ssa.Signature + checkModuleExitCodeSig ssa.Signature + tableGrowSig ssa.Signature + refFuncSig ssa.Signature + memmoveSig ssa.Signature + ensureTermination bool + + // Followings are reset by per function. + + // wasmLocalToVariable maps the index (considered as wasm.Index of locals) + // to the corresponding ssa.Variable. + wasmLocalToVariable [] /* local index to */ ssa.Variable + wasmLocalFunctionIndex wasm.Index + wasmFunctionTypeIndex wasm.Index + wasmFunctionTyp *wasm.FunctionType + wasmFunctionLocalTypes []wasm.ValueType + wasmFunctionBody []byte + wasmFunctionBodyOffsetInCodeSection uint64 + memoryBaseVariable, memoryLenVariable ssa.Variable + needMemory bool + memoryShared bool + globalVariables []ssa.Variable + globalVariablesTypes []ssa.Type + mutableGlobalVariablesIndexes []wasm.Index // index to ^. + needListener bool + needSourceOffsetInfo bool + // br is reused during lowering. + br *bytes.Reader + loweringState loweringState + + knownSafeBounds [] /* ssa.ValueID to */ knownSafeBound + knownSafeBoundsSet []ssa.ValueID + + knownSafeBoundsAtTheEndOfBlocks [] /* ssa.BlockID to */ knownSafeBoundsAtTheEndOfBlock + varLengthKnownSafeBoundWithIDPool wazevoapi.VarLengthPool[knownSafeBoundWithID] + + execCtxPtrValue, moduleCtxPtrValue ssa.Value + + // Following are reused for the known safe bounds analysis. + + pointers []int + bounds [][]knownSafeBoundWithID +} + +type ( + // knownSafeBound represents a known safe bound for a value. + knownSafeBound struct { + // bound is a constant upper bound for the value. + bound uint64 + // absoluteAddr is the absolute address of the value. + absoluteAddr ssa.Value + } + // knownSafeBoundWithID is a knownSafeBound with the ID of the value. + knownSafeBoundWithID struct { + knownSafeBound + id ssa.ValueID + } + knownSafeBoundsAtTheEndOfBlock = wazevoapi.VarLength[knownSafeBoundWithID] +) + +var knownSafeBoundsAtTheEndOfBlockNil = wazevoapi.NewNilVarLength[knownSafeBoundWithID]() + +// NewFrontendCompiler returns a frontend Compiler. +func NewFrontendCompiler(m *wasm.Module, ssaBuilder ssa.Builder, offset *wazevoapi.ModuleContextOffsetData, ensureTermination bool, listenerOn bool, sourceInfo bool) *Compiler { + c := &Compiler{ + m: m, + ssaBuilder: ssaBuilder, + br: bytes.NewReader(nil), + offset: offset, + ensureTermination: ensureTermination, + needSourceOffsetInfo: sourceInfo, + varLengthKnownSafeBoundWithIDPool: wazevoapi.NewVarLengthPool[knownSafeBoundWithID](), + } + c.declareSignatures(listenerOn) + return c +} + +func (c *Compiler) declareSignatures(listenerOn bool) { + m := c.m + c.signatures = make(map[*wasm.FunctionType]*ssa.Signature, len(m.TypeSection)+2) + if listenerOn { + c.listenerSignatures = make(map[*wasm.FunctionType][2]*ssa.Signature, len(m.TypeSection)) + } + for i := range m.TypeSection { + wasmSig := &m.TypeSection[i] + sig := SignatureForWasmFunctionType(wasmSig) + sig.ID = ssa.SignatureID(i) + c.signatures[wasmSig] = &sig + c.ssaBuilder.DeclareSignature(&sig) + + if listenerOn { + beforeSig, afterSig := SignatureForListener(wasmSig) + beforeSig.ID = ssa.SignatureID(i) + ssa.SignatureID(len(m.TypeSection)) + afterSig.ID = ssa.SignatureID(i) + ssa.SignatureID(len(m.TypeSection))*2 + c.listenerSignatures[wasmSig] = [2]*ssa.Signature{beforeSig, afterSig} + c.ssaBuilder.DeclareSignature(beforeSig) + c.ssaBuilder.DeclareSignature(afterSig) + } + } + + begin := ssa.SignatureID(len(m.TypeSection)) + if listenerOn { + begin *= 3 + } + c.memoryGrowSig = ssa.Signature{ + ID: begin, + // Takes execution context and the page size to grow. + Params: []ssa.Type{ssa.TypeI64, ssa.TypeI32}, + // Returns the previous page size. + Results: []ssa.Type{ssa.TypeI32}, + } + c.ssaBuilder.DeclareSignature(&c.memoryGrowSig) + + c.checkModuleExitCodeSig = ssa.Signature{ + ID: c.memoryGrowSig.ID + 1, + // Only takes execution context. + Params: []ssa.Type{ssa.TypeI64}, + } + c.ssaBuilder.DeclareSignature(&c.checkModuleExitCodeSig) + + c.tableGrowSig = ssa.Signature{ + ID: c.checkModuleExitCodeSig.ID + 1, + Params: []ssa.Type{ssa.TypeI64 /* exec context */, ssa.TypeI32 /* table index */, ssa.TypeI32 /* num */, ssa.TypeI64 /* ref */}, + // Returns the previous size. + Results: []ssa.Type{ssa.TypeI32}, + } + c.ssaBuilder.DeclareSignature(&c.tableGrowSig) + + c.refFuncSig = ssa.Signature{ + ID: c.tableGrowSig.ID + 1, + Params: []ssa.Type{ssa.TypeI64 /* exec context */, ssa.TypeI32 /* func index */}, + // Returns the function reference. + Results: []ssa.Type{ssa.TypeI64}, + } + c.ssaBuilder.DeclareSignature(&c.refFuncSig) + + c.memmoveSig = ssa.Signature{ + ID: c.refFuncSig.ID + 1, + // dst, src, and the byte count. + Params: []ssa.Type{ssa.TypeI64, ssa.TypeI64, ssa.TypeI64}, + } + + c.ssaBuilder.DeclareSignature(&c.memmoveSig) + + c.memoryWait32Sig = ssa.Signature{ + ID: c.memmoveSig.ID + 1, + // exec context, timeout, expected, addr + Params: []ssa.Type{ssa.TypeI64, ssa.TypeI64, ssa.TypeI32, ssa.TypeI64}, + // Returns the status. + Results: []ssa.Type{ssa.TypeI32}, + } + c.ssaBuilder.DeclareSignature(&c.memoryWait32Sig) + + c.memoryWait64Sig = ssa.Signature{ + ID: c.memoryWait32Sig.ID + 1, + // exec context, timeout, expected, addr + Params: []ssa.Type{ssa.TypeI64, ssa.TypeI64, ssa.TypeI64, ssa.TypeI64}, + // Returns the status. + Results: []ssa.Type{ssa.TypeI32}, + } + c.ssaBuilder.DeclareSignature(&c.memoryWait64Sig) + + c.memoryNotifySig = ssa.Signature{ + ID: c.memoryWait64Sig.ID + 1, + // exec context, count, addr + Params: []ssa.Type{ssa.TypeI64, ssa.TypeI32, ssa.TypeI64}, + // Returns the number notified. + Results: []ssa.Type{ssa.TypeI32}, + } + c.ssaBuilder.DeclareSignature(&c.memoryNotifySig) +} + +// SignatureForWasmFunctionType returns the ssa.Signature for the given wasm.FunctionType. +func SignatureForWasmFunctionType(typ *wasm.FunctionType) ssa.Signature { + sig := ssa.Signature{ + // +2 to pass moduleContextPtr and executionContextPtr. See the inline comment LowerToSSA. + Params: make([]ssa.Type, len(typ.Params)+2), + Results: make([]ssa.Type, len(typ.Results)), + } + sig.Params[0] = executionContextPtrTyp + sig.Params[1] = moduleContextPtrTyp + for j, typ := range typ.Params { + sig.Params[j+2] = WasmTypeToSSAType(typ) + } + for j, typ := range typ.Results { + sig.Results[j] = WasmTypeToSSAType(typ) + } + return sig +} + +// Init initializes the state of frontendCompiler and make it ready for a next function. +func (c *Compiler) Init(idx, typIndex wasm.Index, typ *wasm.FunctionType, localTypes []wasm.ValueType, body []byte, needListener bool, bodyOffsetInCodeSection uint64) { + c.ssaBuilder.Init(c.signatures[typ]) + c.loweringState.reset() + + c.wasmFunctionTypeIndex = typIndex + c.wasmLocalFunctionIndex = idx + c.wasmFunctionTyp = typ + c.wasmFunctionLocalTypes = localTypes + c.wasmFunctionBody = body + c.wasmFunctionBodyOffsetInCodeSection = bodyOffsetInCodeSection + c.needListener = needListener + c.clearSafeBounds() + c.varLengthKnownSafeBoundWithIDPool.Reset() + c.knownSafeBoundsAtTheEndOfBlocks = c.knownSafeBoundsAtTheEndOfBlocks[:0] +} + +// Note: this assumes 64-bit platform (I believe we won't have 32-bit backend ;)). +const executionContextPtrTyp, moduleContextPtrTyp = ssa.TypeI64, ssa.TypeI64 + +// LowerToSSA lowers the current function to SSA function which will be held by ssaBuilder. +// After calling this, the caller will be able to access the SSA info in *Compiler.ssaBuilder. +// +// Note that this only does the naive lowering, and do not do any optimization, instead the caller is expected to do so. +func (c *Compiler) LowerToSSA() { + builder := c.ssaBuilder + + // Set up the entry block. + entryBlock := builder.AllocateBasicBlock() + builder.SetCurrentBlock(entryBlock) + + // Functions always take two parameters in addition to Wasm-level parameters: + // + // 1. executionContextPtr: pointer to the *executionContext in wazevo package. + // This will be used to exit the execution in the face of trap, plus used for host function calls. + // + // 2. moduleContextPtr: pointer to the *moduleContextOpaque in wazevo package. + // This will be used to access memory, etc. Also, this will be used during host function calls. + // + // Note: it's clear that sometimes a function won't need them. For example, + // if the function doesn't trap and doesn't make function call, then + // we might be able to eliminate the parameter. However, if that function + // can be called via call_indirect, then we cannot eliminate because the + // signature won't match with the expected one. + // TODO: maybe there's some way to do this optimization without glitches, but so far I have no clue about the feasibility. + // + // Note: In Wasmtime or many other runtimes, moduleContextPtr is called "vmContext". Also note that `moduleContextPtr` + // is wazero-specific since other runtimes can naturally use the OS-level signal to do this job thanks to the fact that + // they can use native stack vs wazero cannot use Go-routine stack and have to use Go-runtime allocated []byte as a stack. + c.execCtxPtrValue = entryBlock.AddParam(builder, executionContextPtrTyp) + c.moduleCtxPtrValue = entryBlock.AddParam(builder, moduleContextPtrTyp) + builder.AnnotateValue(c.execCtxPtrValue, "exec_ctx") + builder.AnnotateValue(c.moduleCtxPtrValue, "module_ctx") + + for i, typ := range c.wasmFunctionTyp.Params { + st := WasmTypeToSSAType(typ) + variable := builder.DeclareVariable(st) + value := entryBlock.AddParam(builder, st) + builder.DefineVariable(variable, value, entryBlock) + c.setWasmLocalVariable(wasm.Index(i), variable) + } + c.declareWasmLocals(entryBlock) + c.declareNecessaryVariables() + + c.lowerBody(entryBlock) +} + +// localVariable returns the SSA variable for the given Wasm local index. +func (c *Compiler) localVariable(index wasm.Index) ssa.Variable { + return c.wasmLocalToVariable[index] +} + +func (c *Compiler) setWasmLocalVariable(index wasm.Index, variable ssa.Variable) { + idx := int(index) + if idx >= len(c.wasmLocalToVariable) { + c.wasmLocalToVariable = append(c.wasmLocalToVariable, make([]ssa.Variable, idx+1-len(c.wasmLocalToVariable))...) + } + c.wasmLocalToVariable[idx] = variable +} + +// declareWasmLocals declares the SSA variables for the Wasm locals. +func (c *Compiler) declareWasmLocals(entry ssa.BasicBlock) { + localCount := wasm.Index(len(c.wasmFunctionTyp.Params)) + for i, typ := range c.wasmFunctionLocalTypes { + st := WasmTypeToSSAType(typ) + variable := c.ssaBuilder.DeclareVariable(st) + c.setWasmLocalVariable(wasm.Index(i)+localCount, variable) + + zeroInst := c.ssaBuilder.AllocateInstruction() + switch st { + case ssa.TypeI32: + zeroInst.AsIconst32(0) + case ssa.TypeI64: + zeroInst.AsIconst64(0) + case ssa.TypeF32: + zeroInst.AsF32const(0) + case ssa.TypeF64: + zeroInst.AsF64const(0) + case ssa.TypeV128: + zeroInst.AsVconst(0, 0) + default: + panic("TODO: " + wasm.ValueTypeName(typ)) + } + + c.ssaBuilder.InsertInstruction(zeroInst) + value := zeroInst.Return() + c.ssaBuilder.DefineVariable(variable, value, entry) + } +} + +func (c *Compiler) declareNecessaryVariables() { + if c.needMemory = c.m.MemorySection != nil; c.needMemory { + c.memoryShared = c.m.MemorySection.IsShared + } else if c.needMemory = c.m.ImportMemoryCount > 0; c.needMemory { + for _, imp := range c.m.ImportSection { + if imp.Type == wasm.ExternTypeMemory { + c.memoryShared = imp.DescMem.IsShared + break + } + } + } + + if c.needMemory { + c.memoryBaseVariable = c.ssaBuilder.DeclareVariable(ssa.TypeI64) + c.memoryLenVariable = c.ssaBuilder.DeclareVariable(ssa.TypeI64) + } + + c.globalVariables = c.globalVariables[:0] + c.mutableGlobalVariablesIndexes = c.mutableGlobalVariablesIndexes[:0] + c.globalVariablesTypes = c.globalVariablesTypes[:0] + for _, imp := range c.m.ImportSection { + if imp.Type == wasm.ExternTypeGlobal { + desc := imp.DescGlobal + c.declareWasmGlobal(desc.ValType, desc.Mutable) + } + } + for _, g := range c.m.GlobalSection { + desc := g.Type + c.declareWasmGlobal(desc.ValType, desc.Mutable) + } + + // TODO: add tables. +} + +func (c *Compiler) declareWasmGlobal(typ wasm.ValueType, mutable bool) { + var st ssa.Type + switch typ { + case wasm.ValueTypeI32: + st = ssa.TypeI32 + case wasm.ValueTypeI64, + // Both externref and funcref are represented as I64 since we only support 64-bit platforms. + wasm.ValueTypeExternref, wasm.ValueTypeFuncref: + st = ssa.TypeI64 + case wasm.ValueTypeF32: + st = ssa.TypeF32 + case wasm.ValueTypeF64: + st = ssa.TypeF64 + case wasm.ValueTypeV128: + st = ssa.TypeV128 + default: + panic("TODO: " + wasm.ValueTypeName(typ)) + } + v := c.ssaBuilder.DeclareVariable(st) + index := wasm.Index(len(c.globalVariables)) + c.globalVariables = append(c.globalVariables, v) + c.globalVariablesTypes = append(c.globalVariablesTypes, st) + if mutable { + c.mutableGlobalVariablesIndexes = append(c.mutableGlobalVariablesIndexes, index) + } +} + +// WasmTypeToSSAType converts wasm.ValueType to ssa.Type. +func WasmTypeToSSAType(vt wasm.ValueType) ssa.Type { + switch vt { + case wasm.ValueTypeI32: + return ssa.TypeI32 + case wasm.ValueTypeI64, + // Both externref and funcref are represented as I64 since we only support 64-bit platforms. + wasm.ValueTypeExternref, wasm.ValueTypeFuncref: + return ssa.TypeI64 + case wasm.ValueTypeF32: + return ssa.TypeF32 + case wasm.ValueTypeF64: + return ssa.TypeF64 + case wasm.ValueTypeV128: + return ssa.TypeV128 + default: + panic("TODO: " + wasm.ValueTypeName(vt)) + } +} + +// addBlockParamsFromWasmTypes adds the block parameters to the given block. +func (c *Compiler) addBlockParamsFromWasmTypes(tps []wasm.ValueType, blk ssa.BasicBlock) { + for _, typ := range tps { + st := WasmTypeToSSAType(typ) + blk.AddParam(c.ssaBuilder, st) + } +} + +// formatBuilder outputs the constructed SSA function as a string with a source information. +func (c *Compiler) formatBuilder() string { + return c.ssaBuilder.Format() +} + +// SignatureForListener returns the signatures for the listener functions. +func SignatureForListener(wasmSig *wasm.FunctionType) (*ssa.Signature, *ssa.Signature) { + beforeSig := &ssa.Signature{} + beforeSig.Params = make([]ssa.Type, len(wasmSig.Params)+2) + beforeSig.Params[0] = ssa.TypeI64 // Execution context. + beforeSig.Params[1] = ssa.TypeI32 // Function index. + for i, p := range wasmSig.Params { + beforeSig.Params[i+2] = WasmTypeToSSAType(p) + } + afterSig := &ssa.Signature{} + afterSig.Params = make([]ssa.Type, len(wasmSig.Results)+2) + afterSig.Params[0] = ssa.TypeI64 // Execution context. + afterSig.Params[1] = ssa.TypeI32 // Function index. + for i, p := range wasmSig.Results { + afterSig.Params[i+2] = WasmTypeToSSAType(p) + } + return beforeSig, afterSig +} + +// isBoundSafe returns true if the given value is known to be safe to access up to the given bound. +func (c *Compiler) getKnownSafeBound(v ssa.ValueID) *knownSafeBound { + if int(v) >= len(c.knownSafeBounds) { + return nil + } + return &c.knownSafeBounds[v] +} + +// recordKnownSafeBound records the given safe bound for the given value. +func (c *Compiler) recordKnownSafeBound(v ssa.ValueID, safeBound uint64, absoluteAddr ssa.Value) { + if int(v) >= len(c.knownSafeBounds) { + c.knownSafeBounds = append(c.knownSafeBounds, make([]knownSafeBound, v+1)...) + } + + if exiting := c.knownSafeBounds[v]; exiting.bound == 0 { + c.knownSafeBounds[v] = knownSafeBound{ + bound: safeBound, + absoluteAddr: absoluteAddr, + } + c.knownSafeBoundsSet = append(c.knownSafeBoundsSet, v) + } else if safeBound > exiting.bound { + c.knownSafeBounds[v].bound = safeBound + } +} + +// clearSafeBounds clears the known safe bounds. +func (c *Compiler) clearSafeBounds() { + for _, v := range c.knownSafeBoundsSet { + ptr := &c.knownSafeBounds[v] + ptr.bound = 0 + ptr.absoluteAddr = ssa.ValueInvalid + } + c.knownSafeBoundsSet = c.knownSafeBoundsSet[:0] +} + +// resetAbsoluteAddressInSafeBounds resets the absolute addresses recorded in the known safe bounds. +func (c *Compiler) resetAbsoluteAddressInSafeBounds() { + for _, v := range c.knownSafeBoundsSet { + ptr := &c.knownSafeBounds[v] + ptr.absoluteAddr = ssa.ValueInvalid + } +} + +func (k *knownSafeBound) valid() bool { + return k != nil && k.bound > 0 +} + +func (c *Compiler) allocateVarLengthValues(_cap int, vs ...ssa.Value) ssa.Values { + builder := c.ssaBuilder + pool := builder.VarLengthPool() + args := pool.Allocate(_cap) + args = args.Append(builder.VarLengthPool(), vs...) + return args +} + +func (c *Compiler) finalizeKnownSafeBoundsAtTheEndOfBlock(bID ssa.BasicBlockID) { + _bID := int(bID) + if l := len(c.knownSafeBoundsAtTheEndOfBlocks); _bID >= l { + c.knownSafeBoundsAtTheEndOfBlocks = append(c.knownSafeBoundsAtTheEndOfBlocks, + make([]knownSafeBoundsAtTheEndOfBlock, _bID+1-len(c.knownSafeBoundsAtTheEndOfBlocks))...) + for i := l; i < len(c.knownSafeBoundsAtTheEndOfBlocks); i++ { + c.knownSafeBoundsAtTheEndOfBlocks[i] = knownSafeBoundsAtTheEndOfBlockNil + } + } + p := &c.varLengthKnownSafeBoundWithIDPool + size := len(c.knownSafeBoundsSet) + allocated := c.varLengthKnownSafeBoundWithIDPool.Allocate(size) + // Sort the known safe bounds by the value ID so that we can use the intersection algorithm in initializeCurrentBlockKnownBounds. + sortSSAValueIDs(c.knownSafeBoundsSet) + for _, vID := range c.knownSafeBoundsSet { + kb := c.knownSafeBounds[vID] + allocated = allocated.Append(p, knownSafeBoundWithID{ + knownSafeBound: kb, + id: vID, + }) + } + c.knownSafeBoundsAtTheEndOfBlocks[bID] = allocated + c.clearSafeBounds() +} + +func (c *Compiler) initializeCurrentBlockKnownBounds() { + currentBlk := c.ssaBuilder.CurrentBlock() + switch preds := currentBlk.Preds(); preds { + case 0: + case 1: + pred := currentBlk.Pred(0).ID() + for _, kb := range c.getKnownSafeBoundsAtTheEndOfBlocks(pred).View() { + // Unless the block is sealed, we cannot assume the absolute address is valid: + // later we might add another predecessor that has no visibility of that value. + addr := ssa.ValueInvalid + if currentBlk.Sealed() { + addr = kb.absoluteAddr + } + c.recordKnownSafeBound(kb.id, kb.bound, addr) + } + default: + c.pointers = c.pointers[:0] + c.bounds = c.bounds[:0] + for i := 0; i < preds; i++ { + c.bounds = append(c.bounds, c.getKnownSafeBoundsAtTheEndOfBlocks(currentBlk.Pred(i).ID()).View()) + c.pointers = append(c.pointers, 0) + } + + // If there are multiple predecessors, we need to find the intersection of the known safe bounds. + + outer: + for { + smallestID := ssa.ValueID(math.MaxUint32) + for i, ptr := range c.pointers { + if ptr >= len(c.bounds[i]) { + break outer + } + cb := &c.bounds[i][ptr] + if id := cb.id; id < smallestID { + smallestID = cb.id + } + } + + // Check if current elements are the same across all lists. + same := true + minBound := uint64(math.MaxUint64) + for i := 0; i < preds; i++ { + cb := &c.bounds[i][c.pointers[i]] + if cb.id != smallestID { + same = false + break + } else { + if cb.bound < minBound { + minBound = cb.bound + } + } + } + + if same { // All elements are the same. + // Absolute address cannot be used in the intersection since the value might be only defined in one of the predecessors. + c.recordKnownSafeBound(smallestID, minBound, ssa.ValueInvalid) + } + + // Move pointer(s) for the smallest ID forward (if same, move all). + for i := 0; i < preds; i++ { + cb := &c.bounds[i][c.pointers[i]] + if cb.id == smallestID { + c.pointers[i]++ + } + } + } + } +} + +func (c *Compiler) getKnownSafeBoundsAtTheEndOfBlocks(id ssa.BasicBlockID) knownSafeBoundsAtTheEndOfBlock { + if int(id) >= len(c.knownSafeBoundsAtTheEndOfBlocks) { + return knownSafeBoundsAtTheEndOfBlockNil + } + return c.knownSafeBoundsAtTheEndOfBlocks[id] +} |