Bug 1716041 - Remove unwind exception instruction r=rhunt

This instruction was recently removed from the Wasm exception
handling proposal spec:

  WebAssembly/exception-handling#156

Differential Revision: https://phabricator.services.mozilla.com/D118080

Author: takikawa

js/src/jit-test/lib/wasm-binary.js

@@ -152,7 +152,7 @@ const MozPrefix = 0xff;
 
 const definedOpcodes =
     [0x00, 0x01, 0x02, 0x03, 0x04, 0x05,
-     ...(wasmExceptionsEnabled() ? [0x06, 0x07, 0x08, 0x09, 0x0a] : []),
+     ...(wasmExceptionsEnabled() ? [0x06, 0x07, 0x08, 0x09] : []),
      0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
      0x10, 0x11,
      ...(wasmExceptionsEnabled() ? [0x18, 0x19] : []),

js/src/jit-test/tests/wasm/exceptions/instructions.js

@@ -989,123 +989,3 @@ assertEq(
   ).exports.f(),
   42
 );
-
-// Test try-unwind blocks.
-assertEq(
-  wasmEvalText(
-    `(module
-       (func (export "f") (result i32)
-         try (result i32)
-           i32.const 42
-         unwind
-         end))`
-  ).exports.f(),
-  42
-);
-
-assertEq(
-  wasmEvalText(
-    `(module
-       (func (export "f") (result i32)
-         try (result i32)
-           i32.const 42
-           br 0
-         unwind
-         end))`
-  ).exports.f(),
-  42
-);
-
-assertEq(
-  wasmEvalText(
-    `(module
-       (event $exn)
-       (func (export "f") (result i32)
-         try (result i32)
-           throw $exn
-         unwind
-           i32.const 42
-           br 0
-         end))`
-  ).exports.f(),
-  42
-);
-
-assertEq(
-  wasmEvalText(
-    `(module
-       (event $exn)
-       (func (export "f") (result i32)
-         try (result i32)
-           throw $exn
-         unwind
-           i32.const 42
-           return
-         end))`
-  ).exports.f(),
-  42
-);
-
-assertEq(
-  wasmEvalText(
-    `(module
-       (type (func))
-       (event $exn (type 0))
-       (func (export "f") (result i32) (local i32)
-         try
-           try
-             throw $exn
-           unwind
-             i32.const 1
-             local.set 0
-           end
-         catch $exn
-         end
-         local.get 0))`
-  ).exports.f(),
-  1
-);
-
-// Test the interaction between delegate and unwind.
-assertEq(
-  wasmEvalText(
-    `(module
-       (event $exn)
-       (func (export "f") (result i32) (local i32)
-         try
-           try
-             try
-               throw $exn
-             delegate 0
-           unwind
-             i32.const 42
-             local.set 0
-           end
-         catch_all
-         end
-         local.get 0))`
-  ).exports.f(),
-  42
-);
-
-assertEq(
-  wasmEvalText(
-    `(module
-       (type (func))
-       (event $exn (type 0))
-       (func (export "f") (result i32) (local i32)
-         try $l
-           try
-             try
-               throw $exn
-             delegate 1
-           unwind
-             i32.const 27
-             local.set 0
-           end
-         catch_all
-         end
-         local.get 0))`
-  ).exports.f(),
-  0
-);

js/src/jit-test/tests/wasm/exceptions/throw-to-js.js

@@ -242,16 +242,3 @@ assertWasmThrowsExn(() =>
          delegate 0))`
   ).exports.f()
 );
-
-// Test unwind rethrowing on exit.
-assertWasmThrowsExn(() =>
-  wasmEvalText(
-    `(module
-       (event $exn (param))
-       (func (export "f") (result i32)
-         try (result i32)
-           throw $exn
-         unwind
-         end))`
-  ).exports.f()
-);

js/src/jit-test/tests/wasm/exceptions/validation.js

@@ -97,7 +97,7 @@ function testValidateDecode() {
         }),
       ]),
     ]),
-    /try without catch or unwind not allowed/
+    /try without catch or catch_all not allowed/
   );
 
   // Rethrow must have a depth argument.
@@ -641,66 +641,6 @@ function testValidateDelegate() {
   );
 }
 
-function testValidateUnwind() {
-  wasmValidateText(
-    `(module
-       (event $exn (param))
-       (func (local i32)
-         try
-           throw $exn
-         unwind
-           i32.const 1
-           local.set 0
-        end))`
-  );
-
-  wasmValidateText(
-    `(module
-       (event $exn (param))
-       (func (result i32)
-         try (result i32)
-           i32.const 1
-           br 0
-         unwind
-           i32.const 2
-           br 0
-         end))`
-  );
-
-  wasmFailValidateText(
-    `(module
-       (event $exn (param))
-       (func (export "f")
-         try (result i32)
-           (i32.const 1)
-         unwind
-         end))`,
-    /unused values not explicitly dropped by end of block/
-  );
-
-  wasmFailValidateText(
-    `(module
-       (event $exn (param))
-       (func (local i32)
-         try
-           throw $exn
-         unwind
-           (i32.const 1)
-         end))`,
-    /unused values not explicitly dropped by end of block/
-  );
-
-  wasmFailValidateText(
-    `(module (func unwind))`,
-    /unwind can only be used within a try/
-  );
-
-  wasmFailValidateText(
-    `(module (func try unwind rethrow 0 end))`,
-    /rethrow target was not a catch block/
-  );
-}
-
 testValidateDecode();
 testValidateThrow();
 testValidateTryCatch();
@@ -709,4 +649,3 @@ testValidateCatchAll();
 testValidateExnPayload();
 testValidateRethrow();
 testValidateDelegate();
-testValidateUnwind();

js/src/wasm/WasmBaselineCompile.cpp

@@ -8385,7 +8385,6 @@ class BaseCompiler final : public BaseCompilerInterface {
   [[nodiscard]] bool emitCatch();
   [[nodiscard]] bool emitCatchAll();
   [[nodiscard]] bool emitDelegate();
-  [[nodiscard]] bool emitUnwind();
   [[nodiscard]] bool emitThrow();
   [[nodiscard]] bool emitRethrow();
 #endif
@@ -8440,7 +8439,6 @@ class BaseCompiler final : public BaseCompilerInterface {
   [[nodiscard]] bool endIfThenElse(ResultType type);
 #ifdef ENABLE_WASM_EXCEPTIONS
   [[nodiscard]] bool endTryCatch(ResultType type);
-  [[nodiscard]] bool endTryUnwind(ResultType type);
 #endif
 
   void doReturn(ContinuationKind kind);
@@ -10273,11 +10271,6 @@ bool BaseCompiler::emitEnd() {
         return false;
       }
       break;
-    case LabelKind::Unwind:
-      if (!endTryUnwind(type)) {
-        return false;
-      }
-      break;
 #endif
   }
 
@@ -10786,57 +10779,6 @@ bool BaseCompiler::emitDelegate() {
   return pushBlockResults(resultType);
 }
 
-bool BaseCompiler::emitUnwind() {
-  ResultType resultType;
-  NothingVector unused_tryValues;
-
-  if (!iter_.readUnwind(&resultType, &unused_tryValues)) {
-    return false;
-  }
-
-  Control& tryUnwind = controlItem();
-
-  // End the try branch like the first catch block in a try-catch.
-  if (deadCode_) {
-    fr.resetStackHeight(tryUnwind.stackHeight, resultType);
-    popValueStackTo(tryUnwind.stackSize);
-  } else {
-    MOZ_ASSERT(stk_.length() == tryUnwind.stackSize + resultType.length());
-    popBlockResults(resultType, tryUnwind.stackHeight, ContinuationKind::Jump);
-    freeResultRegisters(resultType);
-    masm.jump(&tryUnwind.label);
-    MOZ_ASSERT(!tryUnwind.bceSafeOnExit);
-    MOZ_ASSERT(!tryUnwind.deadOnArrival);
-  }
-
-  deadCode_ = tryUnwind.deadOnArrival;
-
-  if (deadCode_) {
-    return true;
-  }
-
-  bceSafe_ = 0;
-
-  // Create an exception landing pad for the unwind instructions.
-  //
-  // We bind otherLabel so that `delegate` can jump here as well.
-  masm.bind(&tryUnwind.otherLabel);
-  fr.setStackHeight(tryUnwind.stackHeight);
-
-  // Push the exception reference so that the end of the `unwind` can throw.
-  RegRef exn = RegRef(WasmExceptionReg);
-  needRef(exn);
-  pushRef(exn);
-
-  WasmTryNoteVector& tryNotes = masm.tryNotes();
-  WasmTryNote& tryNote = tryNotes[tryUnwind.tryNoteIndex];
-  tryNote.end = masm.currentOffset();
-  tryNote.entryPoint = tryNote.end;
-  tryNote.framePushed = masm.framePushed();
-
-  return true;
-}
-
 bool BaseCompiler::endTryCatch(ResultType type) {
   uint32_t lineOrBytecode = readCallSiteLineOrBytecode();
 
@@ -10945,45 +10887,6 @@ bool BaseCompiler::endTryCatch(ResultType type) {
   return pushBlockResults(type);
 }
 
-bool BaseCompiler::endTryUnwind(ResultType type) {
-  uint32_t lineOrBytecode = readCallSiteLineOrBytecode();
-  Control& tryUnwind = controlItem();
-
-  if (deadCode_) {
-    fr.resetStackHeight(tryUnwind.stackHeight, type);
-    popValueStackTo(tryUnwind.stackSize);
-  } else {
-    // An unwind should have no results so only the exception reference will
-    // remain here on top of the original stack.
-    MOZ_ASSERT(stk_.length() == tryUnwind.stackSize + 1);
-
-    RegRef exn = popRef();
-
-    if (!throwFrom(exn, lineOrBytecode)) {
-      return false;
-    }
-    MOZ_ASSERT(stk_.length() == tryUnwind.stackSize);
-    MOZ_ASSERT(!tryUnwind.bceSafeOnExit);
-    MOZ_ASSERT(!tryUnwind.deadOnArrival);
-  }
-
-  deadCode_ = tryUnwind.deadOnArrival;
-
-  if (deadCode_) {
-    return true;
-  }
-
-  // The try branch may jump here.
-  if (tryUnwind.label.used()) {
-    masm.bind(&tryUnwind.label);
-  }
-
-  captureResultRegisters(type);
-  bceSafe_ = tryUnwind.bceSafeOnExit;
-
-  return pushBlockResults(type);
-}
-
 bool BaseCompiler::emitThrow() {
   uint32_t lineOrBytecode = readCallSiteLineOrBytecode();
   uint32_t exnIndex;
@@ -15746,11 +15649,6 @@ bool BaseCompiler::emitBody() {
         CHECK(emitDelegate());
         iter_.popDelegate();
         NEXT();
-      case uint16_t(Op::Unwind):
-        if (!moduleEnv_.exceptionsEnabled()) {
-          return iter_.unrecognizedOpcode(&op);
-        }
-        CHECK_NEXT(emitUnwind());
       case uint16_t(Op::Throw):
         if (!moduleEnv_.exceptionsEnabled()) {
           return iter_.unrecognizedOpcode(&op);

js/src/wasm/WasmConstants.h

@@ -222,7 +222,6 @@ enum class Op {
   Catch = 0x07,
   Throw = 0x08,
   Rethrow = 0x09,
-  Unwind = 0x0a,
 #endif
   End = 0x0b,
   Br = 0x0c,