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revert asm logic

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This commit is contained in:
wenshao 2025-03-03 19:48:12 +08:00
parent 0e3eaac306
commit 914aed5ab1
3 changed files with 32 additions and 2 deletions
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3
core/src/main/java/com/alibaba/fastjson2/internal/asm/Constants.java
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@ -123,7 +123,8 @@ final class Constants {
// static final int ASTORE_3 = 78;
static final int WIDE = 196;
static final int GOTO_W = 200;
// static final int JSR_W = 201;
static final int JSR_W = 201;
static final int ASM_GOTO_W = 220;
// Constants to convert between normal and wide jump instructions.

30
core/src/main/java/com/alibaba/fastjson2/internal/asm/MethodWriter.java
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@ -597,7 +597,32 @@ public final class MethodWriter {
boolean nextInsnIsJumpTarget = false;
if ((label.flags & Label.FLAG_RESOLVED) != 0
&& label.bytecodeOffset - code.length < Short.MIN_VALUE) {
throw new JSONException("not supported");
// Case of a backward jump with an offset < -32768. In this case we automatically replace GOTO
// with GOTO_W, JSR with JSR_W and IFxxx <l> with IFNOTxxx <L> GOTO_W <l> L:..., where
// IFNOTxxx is the "opposite" opcode of IFxxx (e.g. IFNE for IFEQ) and where <L> designates
// the instruction just after the GOTO_W.
if (baseOpcode == Opcodes.GOTO) {
code.putByte(Constants.GOTO_W);
} else if (baseOpcode == Opcodes.JSR) {
code.putByte(Constants.JSR_W);
} else {
// Put the "opposite" opcode of baseOpcode. This can be done by flipping the least
// significant bit for IFNULL and IFNONNULL, and similarly for IFEQ ... IF_ACMPEQ (with a
// pre and post offset by 1). The jump offset is 8 bytes (3 for IFNOTxxx, 5 for GOTO_W).
code.putByte(baseOpcode >= Opcodes.IFNULL ? baseOpcode ^ 1 : ((baseOpcode + 1) ^ 1) - 1);
code.putShort(8);
// Here we could put a GOTO_W in theory, but if ASM specific instructions are used in this
// method or another one, and if the class has frames, we will need to insert a frame after
// this GOTO_W during the additional ClassReader -> ClassWriter round trip to remove the ASM
// specific instructions. To not miss this additional frame, we need to use an ASM_GOTO_W
// here, which has the unfortunate effect of forcing this additional round trip (which in
// some case would not have been really necessary, but we can't know this at this point).
code.putByte(Constants.ASM_GOTO_W);
hasAsmInstructions = true;
// The instruction after the GOTO_W becomes the target of the IFNOT instruction.
nextInsnIsJumpTarget = true;
}
label.put(code, code.length - 1, true);
} else if (baseOpcode != opcode) {
// Case of a GOTO_W or JSR_W specified by the user (normally ClassReader when used to remove
// ASM specific instructions). In this case we keep the original instruction.
@ -629,6 +654,9 @@ public final class MethodWriter {
// If the next instruction starts a new basic block, call visitLabel to add the label of this
// instruction as a successor of the current block, and to start a new basic block.
if (nextBasicBlock != null) {
if (nextInsnIsJumpTarget) {
nextBasicBlock.flags |= Label.FLAG_JUMP_TARGET;
}
visitLabel(nextBasicBlock);
}
if (baseOpcode == Opcodes.GOTO) {

1
core/src/main/java/com/alibaba/fastjson2/internal/asm/Opcodes.java
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@ -154,6 +154,7 @@ public interface Opcodes {
int IF_ACMPEQ = 165; // -
int IF_ACMPNE = 166; // -
int GOTO = 167; // -
int JSR = 168; // -
int RET = 169; // visitVarInsn
int TABLESWITCH = 170; // visiTableSwitchInsn
int LOOKUPSWITCH = 171; // visitLookupSwitch