org.jikesrvm.compilers.opt.controlflow

Class BranchSimplifier

java.lang.Object

org.jikesrvm.compilers.opt.controlflow.BranchSimplifier

public abstract class BranchSimplifier
extends Object

Simplify and canonicalize conditional branches with constant operands.

This module performs no analysis, it simply attempts to simplify any branching instructions of a basic block that have constant operands. The intent is that analysis modules can call this transformation engine, allowing us to share the simplification code among multiple analysis modules.

Constructor Summary

Constructors

Constructor and Description
BranchSimplifier()

Method Summary

Modifier and Type	Method and Description
private static void	insertTrueGuard(Instruction inst, RegisterOperand guard)
(package private) static boolean	processIfCmp(IR ir, BasicBlock bb, Instruction s)
(package private) static boolean	processIfCmp2(IR ir, BasicBlock bb, Instruction s)
(package private) static boolean	processInlineGuard(IR ir, BasicBlock bb, Instruction s)
(package private) static boolean	processLookupSwitch(IR ir, BasicBlock bb, Instruction s)
(package private) static boolean	processTableSwitch(IR ir, BasicBlock bb, Instruction s)
private static void	removeBranchesAfterGotos(BasicBlock bb) To maintain IR integrity, remove any branches that are after the first GOTO in the basic block.
static boolean	simplify(BasicBlock bb, IR ir) Given a basic block, attempt to simplify any conditional branch instructions with constant operands.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

BranchSimplifier

public BranchSimplifier()

Method Detail

simplify

public static boolean simplify(BasicBlock bb,
                               IR ir)

Given a basic block, attempt to simplify any conditional branch instructions with constant operands. The instruction will be mutated in place. The control flow graph will be updated, but the caller is responsible for calling BranchOptmizations after simplify has been called on all basic blocks in the IR to remove unreachable code.

Parameters:

bb - the basic block to simplify

ir - the governing IR

Returns:

true if we do something, false otherwise.

processIfCmp

static boolean processIfCmp(IR ir,
                            BasicBlock bb,
                            Instruction s)

processIfCmp2

static boolean processIfCmp2(IR ir,
                             BasicBlock bb,
                             Instruction s)

processLookupSwitch

static boolean processLookupSwitch(IR ir,
                                   BasicBlock bb,
                                   Instruction s)

processTableSwitch

static boolean processTableSwitch(IR ir,
                                  BasicBlock bb,
                                  Instruction s)

processInlineGuard

static boolean processInlineGuard(IR ir,
                                  BasicBlock bb,
                                  Instruction s)

removeBranchesAfterGotos

private static void removeBranchesAfterGotos(BasicBlock bb)

To maintain IR integrity, remove any branches that are after the first GOTO in the basic block.

Parameters:

bb - the block to search for gotos

insertTrueGuard

private static void insertTrueGuard(Instruction inst,
                                    RegisterOperand guard)