| // Copyright 2015 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package ssa |
| |
| import ( |
| "fmt" |
| "strings" |
| ) |
| |
| // Block represents a basic block in the control flow graph of a function. |
| type Block struct { |
| // A unique identifier for the block. The system will attempt to allocate |
| // these IDs densely, but no guarantees. |
| ID ID |
| |
| // The kind of block this is. |
| Kind BlockKind |
| |
| // Subsequent blocks, if any. The number and order depend on the block kind. |
| // All successors must be distinct (to make phi values in successors unambiguous). |
| Succs []*Block |
| |
| // Inverse of successors. |
| // The order is significant to Phi nodes in the block. |
| Preds []*Block |
| // TODO: predecessors is a pain to maintain. Can we somehow order phi |
| // arguments by block id and have this field computed explicitly when needed? |
| |
| // A value that determines how the block is exited. Its value depends on the kind |
| // of the block. For instance, a BlockIf has a boolean control value and BlockExit |
| // has a memory control value. |
| Control *Value |
| |
| // The unordered set of Values that define the operation of this block. |
| // The list must include the control value, if any. (TODO: need this last condition?) |
| // After the scheduling pass, this list is ordered. |
| Values []*Value |
| |
| // The containing function |
| Func *Func |
| } |
| |
| // kind control successors |
| // ------------------------------------------ |
| // Exit return mem [] |
| // Plain nil [next] |
| // If a boolean Value [then, else] |
| // Call mem [nopanic, panic] (control opcode should be OpCall or OpStaticCall) |
| type BlockKind int8 |
| |
| const ( |
| BlockExit BlockKind = iota // no successors. There should only be 1 of these. |
| BlockPlain // a single successor |
| BlockIf // 2 successors, if control goto Succs[0] else goto Succs[1] |
| BlockCall // 2 successors, normal return and panic |
| // TODO(khr): BlockPanic for the built-in panic call, has 1 edge to the exit block |
| BlockUnknown |
| |
| // 386/amd64 variants of BlockIf that take the flags register as an arg |
| BlockEQ |
| BlockNE |
| BlockLT |
| BlockLE |
| BlockGT |
| BlockGE |
| BlockULT |
| BlockULE |
| BlockUGT |
| BlockUGE |
| ) |
| |
| //go:generate stringer -type=BlockKind |
| |
| // short form print |
| func (b *Block) String() string { |
| return fmt.Sprintf("b%d", b.ID) |
| } |
| |
| // long form print |
| func (b *Block) LongString() string { |
| s := strings.TrimPrefix(b.Kind.String(), "Block") |
| if b.Control != nil { |
| s += fmt.Sprintf(" %s", b.Control) |
| } |
| if len(b.Succs) > 0 { |
| s += " ->" |
| for _, c := range b.Succs { |
| s += " " + c.String() |
| } |
| } |
| return s |
| } |