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misc: Change aggressive variable pruning to instead shift accepted ra…
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@Col-E
Col-E committed Jan 11, 2025
1 parent 6e4ee7f commit 1f1424f
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Showing 3 changed files with 136 additions and 81 deletions.
200 changes: 125 additions & 75 deletions jasm-composition-jvm/src/main/java/me/darknet/assembler/printer/JvmMethodPrinter.java
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Original file line number Diff line number Diff line change
@@ -1,27 +1,32 @@
package me.darknet.assembler.printer;

import dev.xdark.blw.annotation.Element;
import dev.xdark.blw.classfile.AccessFlag;
import dev.xdark.blw.classfile.Method;
import dev.xdark.blw.code.Code;
import dev.xdark.blw.code.CodeElement;
import dev.xdark.blw.code.Label;
import dev.xdark.blw.code.attribute.Local;
import dev.xdark.blw.code.generic.GenericLabel;
import dev.xdark.blw.code.instruction.VarInstruction;
import dev.xdark.blw.type.ClassType;
import dev.xdark.blw.type.PrimitiveType;
import dev.xdark.blw.type.Type;
import dev.xdark.blw.type.Types;
import me.darknet.assembler.compile.analysis.jvm.IndexedStraightforwardSimulation;
import me.darknet.assembler.helper.Variables;
import me.darknet.assembler.util.BlwOpcodes;
import me.darknet.assembler.util.EscapeUtil;
import me.darknet.assembler.util.LabelUtil;

import dev.xdark.blw.classfile.AccessFlag;
import dev.xdark.blw.classfile.Method;
import dev.xdark.blw.code.CodeElement;
import dev.xdark.blw.code.Label;
import dev.xdark.blw.code.attribute.Local;
import dev.xdark.blw.type.ClassType;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.util.*;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;

public class JvmMethodPrinter implements MethodPrinter {

Expand Down Expand Up @@ -66,27 +71,24 @@ public JvmMethodPrinter(Method method) {
name = prefix + (i++);
}

int start = local.start().getIndex();
int end = local.end().getIndex();

if (ctx.aggressivelyDropVars) {
// Validate that the variable scope isn't busted.
//
// Kotlin is stupid for example, because it will say the variable begins at an offset beyond
// where the variable is first assigned (by several instructions). So the code assigning the value
// is outside the variable scope, and usage of the then assigned variable is in-scope.
//
// We'll just do a blunt check to see if the variable is assigned between the last label and
// the supposed starting offset of this local. If we find that the variable is used before the start
// of the local we will just not acknowledge this variable as a valid candidate to use when picking
// variable names. This will result in some valid label ranges being discarded,
// but it is safer to more aggressively discard than to fall into the trap mentioned above.
int priorLabelOffset = findPriorLabelOffset(code, start);
if (isVarUsedInRange(code, index, priorLabelOffset, start))
continue;
}

locals.add(new Variables.Local(index, start, end, name, descriptor));
int start = local.start().getIndex();
int end = local.end().getIndex();

// Expand the range of the variable if necessary.
// In many cases the range of the variable follows this example:
//
// Variable[start=x, end=...]
// - astore foo
// - label x
// - aload foo
//
// Thus we will want to move the 'start' backwards to reach to the first write.
int priorLabelOffset = findPriorLabelOffset(code, start);
int variableWriteInRange = getVariableWriteInRange(code, index, priorLabelOffset, start);
if (variableWriteInRange >= 0 && !isVariableInstructionInOtherScope(variableWriteInRange, code, local))
start = variableWriteInRange;

locals.add(new Variables.Local(index, start, end, name, descriptor));
nameToType.put(name, varType);
}
}
Expand All @@ -107,27 +109,75 @@ public JvmMethodPrinter(Method method) {
if (Types.category(type) > 1)
offset++;
}
return new Variables(parameterNames, locals);
return new Variables(parameterNames, locals);
}

private static boolean isVarUsedInRange(Code code, int variableIndex, int start, int end) {
List<CodeElement> elements = code.elements();
for (int i = start; i < end; i++)
if (elements.get(i) instanceof VarInstruction varInsn && varInsn.variableIndex() == variableIndex)
return true;
return false;
}

private static int findPriorLabelOffset(Code code, int start) {
List<CodeElement> elements = code.elements();
for (int i = start - 1; i >= 0; i--) {
if (elements.get(i) instanceof Label)
return i;
}
return 0;
}

@Override
/**
* Used to check if an instruction <i>(xload/xstore)</i> is covered by a variable scope over than the given one.
*
* @param variableInstructionIndex
* Index of variable instruction in {@link Code#elements()}.
* @param code
* Code to check for other variable scopes.
* @param scope
* The current variable scope.
*
* @return {@code true} when the given instruction index is covered by a different {@link Local} scope other than the given one.
* {@code false} when the given instruction index is not covered by a variable scope other than the given one.
*/
private boolean isVariableInstructionInOtherScope(int variableInstructionIndex, @NotNull Code code, @NotNull Local scope) {
for (Local local : code.localVariables()) {
if (local == scope)
continue;
if (scope.index() == local.index()
&& variableInstructionIndex >= local.start().getIndex()
&& variableInstructionIndex <= local.end().getIndex())
return true;
}
return false;
}

/**
* @param code
* Code to check for other variable instructions in.
* @param variableIndex
* Local variable index to filter variable instructions by.
* @param start
* Start range in {@link Code#elements()}.
* @param end
* End range in {@link Code#elements()}.
*
* @return Latest instruction index in {@link Code#elements()} of a variable instruction
* writing to the given variable index within the given range. Otherwise, {@code -1}.
*/
private static int getVariableWriteInRange(@NotNull Code code, int variableIndex, int start, int end) {
List<CodeElement> elements = code.elements();
for (int i = end; i >= start; i--)
if (elements.get(i) instanceof VarInstruction varInsn
&& varInsn.variableIndex() == variableIndex
&& BlwOpcodes.isVarStore(varInsn.opcode()))
return i;
return -1;
}

/**
* @param code
* Code to check for labels.
* @param start
* Start index of search.
*
* @return Latest index of a label before the given start
*/
private static int findPriorLabelOffset(@NotNull Code code, int start) {
List<CodeElement> elements = code.elements();
for (int i = start - 1; i >= 0; i--) {
if (elements.get(i) instanceof Label)
return i;
}
return 0;
}

@Override
public void print(PrintContext<?> ctx) {
memberPrinter.printAttributes(ctx);
var obj = memberPrinter.printDeclaration(ctx).literal(method.name()).print(" ")
Expand Down Expand Up @@ -213,7 +263,7 @@ public void print(PrintContext<?> ctx) {
private static @NotNull String getName(List<Variables.Local> locals, int i) {
String name = null;

// search for parameter name in local variables, first reference of the index which matches the type
// search for parameter name in local variables, first reference of the index which matches the type
for (Variables.Local local : locals) {
if (local.index() == i) {
name = local.name();
Expand All @@ -239,30 +289,30 @@ private static Map<Integer, String> getLabelNames(PrintContext<?> ctx, List<Code
return labelNames;
}

private static boolean requiresDeconfliction(@NotNull Type varType, @Nullable Type existingVarType) {
// If there is no existing type, no conflicts are possible.
if (existingVarType == null)
return false;

// If the var types are different (primitive vs class type) then we MUST deconflict.
if (varType.getClass() != existingVarType.getClass())
return true;

// If the class types do not match we MUST deconflict.
if (varType instanceof ClassType varClass
&& existingVarType instanceof ClassType existingClass
&& !varClass.descriptor().equals(existingClass.descriptor()))
return true;

// If the primitive types do not match we MUST deconflict.
return varType instanceof PrimitiveType varPrim
&& existingVarType instanceof PrimitiveType existingPrim
&& varPrim.kind() != existingPrim.kind();
}

private static @NotNull String escapeName(@NotNull String name, int index, boolean isStatic) {
if (name.equals("this") && !(index == 0 && !isStatic))
return "p" + index;
return EscapeUtil.escapeLiteral(name);
}
private static boolean requiresDeconfliction(@NotNull Type varType, @Nullable Type existingVarType) {
// If there is no existing type, no conflicts are possible.
if (existingVarType == null)
return false;

// If the var types are different (primitive vs class type) then we MUST deconflict.
if (varType.getClass() != existingVarType.getClass())
return true;

// If the class types do not match we MUST deconflict.
if (varType instanceof ClassType varClass
&& existingVarType instanceof ClassType existingClass
&& !varClass.descriptor().equals(existingClass.descriptor()))
return true;

// If the primitive types do not match we MUST deconflict.
return varType instanceof PrimitiveType varPrim
&& existingVarType instanceof PrimitiveType existingPrim
&& varPrim.kind() != existingPrim.kind();
}

private static @NotNull String escapeName(@NotNull String name, int index, boolean isStatic) {
if (name.equals("this") && !(index == 0 && !isStatic))
return "p" + index;
return EscapeUtil.escapeLiteral(name);
}
}
11 changes: 11 additions & 0 deletions jasm-composition-jvm/src/main/java/me/darknet/assembler/util/BlwOpcodes.java
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,17 @@ public class BlwOpcodes {
private static final Map<String, Integer> opcodes = new HashMap<>();
private static final Map<String, Integer> filteredOpcodes = new HashMap<>();

public static boolean isVarStore(int opcode) {
return switch (opcode) {
case JavaOpcodes.ASTORE,
JavaOpcodes.ISTORE,
JavaOpcodes.FSTORE,
JavaOpcodes.DSTORE,
JavaOpcodes.LSTORE -> true;
default -> false;
};
}

public static int opcode(String name) {
if (name.endsWith("interface")) {
String prefix = name.substring(0, name.length() - 9);
Expand Down
6 changes: 0 additions & 6 deletions jasm-core/src/main/java/me/darknet/assembler/printer/PrintContext.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,6 @@ public class PrintContext<T extends PrintContext<?>> {
protected Writer writer;
protected String labelPrefix;
protected boolean debugTryCatchRanges;
protected boolean aggressivelyDropVars;
protected boolean ignoreExistingVariableNames;

public PrintContext(String indentStep, Writer writer) {
Expand All @@ -35,7 +34,6 @@ public PrintContext(String indentStep) {

public PrintContext(PrintContext<?> ctx) {
this.debugTryCatchRanges = ctx.debugTryCatchRanges;
this.aggressivelyDropVars = ctx.aggressivelyDropVars;
this.ignoreExistingVariableNames = ctx.ignoreExistingVariableNames;
this.indentStep = ctx.indentStep;
this.writer = ctx.writer;
Expand All @@ -46,10 +44,6 @@ public void setIndentStep(String indent) {
this.indentStep = indent;
}

public void setAggressivelyDropVars(boolean aggressivelyDropVars) {
this.aggressivelyDropVars = aggressivelyDropVars;
}

public void setDebugTryCatchRanges(boolean debugTryCatchRanges) {
this.debugTryCatchRanges = debugTryCatchRanges;
}
Expand Down

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