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program.go
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program.go
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package ir
import (
"fmt"
"go/token"
"strings"
"github.com/andrewarchi/nebula/internal/digraph"
)
// Program is a set of interconnected basic blocks.
type Program struct {
Name string
Blocks []*BasicBlock
Entry *BasicBlock
NextBlockID int
File *token.File
}
// TrimUnreachable removes uncalled blocks.
func (p *Program) TrimUnreachable() {
// TODO traverse in topological order
i := 0
for _, block := range p.Blocks {
if len(block.Callers) == 0 {
block.Disconnect()
} else {
p.Blocks[i] = block
i++
}
}
if i != len(p.Blocks)-1 {
p.Blocks = p.Blocks[:i]
p.RenumberBlockIDs()
}
}
// RenumberBlockIDs cleans up block IDs to match the block index.
func (p *Program) RenumberBlockIDs() {
for i, block := range p.Blocks {
block.ID = i
}
p.NextBlockID = len(p.Blocks)
}
// Digraph constructs a digraph representing control flow.
func (p *Program) Digraph() digraph.Digraph {
g := make(digraph.Digraph, p.NextBlockID)
for _, block := range p.Blocks {
for _, edge := range block.Succs() {
g.AddEdge(block.ID, edge.ID)
}
}
return g
}
// DotDigraph creates a control flow graph in the Graphviz DOT format.
func (p *Program) DotDigraph() string {
var b strings.Builder
b.WriteString("digraph {\n")
b.WriteString(" entry[shape=point];\n")
p.RenumberBlockIDs()
for i, scc := range p.Digraph().SCCs() {
fmt.Fprintf(&b, " subgraph cluster_%d {\n", i)
for _, node := range scc {
block := p.Blocks[node]
fmt.Fprintf(&b, " block_%d[label=\"%s\"", block.ID, block.Name())
if _, ok := block.Terminator.(*ExitTerm); ok {
b.WriteString(" peripheries=2")
}
b.WriteString("];\n")
}
b.WriteString(" }\n")
}
b.WriteByte('\n')
fmt.Fprintf(&b, " entry -> block_%d;\n", p.Entry.ID)
for _, block := range p.Blocks {
switch term := block.Terminator.(type) {
case *CallTerm:
fmt.Fprintf(&b, " block_%d -> block_%d[label=\"call\"];\n", block.ID, term.succs[0].ID)
case *JmpTerm:
fmt.Fprintf(&b, " block_%d -> block_%d[label=\"jmp\"];\n", block.ID, term.succs[0].ID)
case *JmpCondTerm:
fmt.Fprintf(&b, " block_%d -> block_%d[label=\"true\"];\n", block.ID, term.succs[0].ID)
fmt.Fprintf(&b, " block_%d -> block_%d[label=\"false\"];\n", block.ID, term.succs[1].ID)
case *RetTerm:
for _, caller := range block.Callers {
fmt.Fprintf(&b, " block_%d -> block_%d[label=\"ret\\n%s\"];\n", block.ID, caller.Next.ID, caller.Name())
}
case *ExitTerm:
default:
panic("ir: unrecognized terminator type")
}
}
b.WriteString("}\n")
return b.String()
}
func (p *Program) String() string {
return NewFormatter().FormatProgram(p)
}
func (err *RetUnderflowError) addTrace(err2 *RetUnderflowError, trace *BasicBlock) *RetUnderflowError {
if err2 == nil {
return err
}
for i := range err2.Traces {
err2.Traces[i] = append(err2.Traces[i], trace)
}
if err == nil {
return err2
}
err.Traces = append(err.Traces, err2.Traces...)
return err
}
func (err *RetUnderflowError) Error() string {
if err == nil {
return "<nil>"
}
if len(err.Traces) == 0 {
return "call stack underflow"
}
var b strings.Builder
b.WriteString("call stack underflow\n")
for _, trace := range err.Traces {
fmt.Fprintf(&b, " %s: ", trace[0].Name())
for i := len(trace) - 1; i >= 0; i-- {
b.WriteString(trace[i].Name())
if i != 0 {
b.WriteString(" -> ")
}
}
b.WriteByte('\n')
}
return b.String()
}