Add a level of indirection to exception handler addresses.

src/arm/macro-assembler-arm.cc

Index: src/arm/macro-assembler-arm.cc
diff --git a/src/arm/macro-assembler-arm.cc b/src/arm/macro-assembler-arm.cc
index ee484d976dfd9c18352517b116b36e8f52f118ef..85de7d46dcdb5ba9ab455f870dc25f40a716a97d 100644
--- a/src/arm/macro-assembler-arm.cc
+++ b/src/arm/macro-assembler-arm.cc
@@ -1158,46 +1158,48 @@ void MacroAssembler::DebugBreak() {
 
 
 void MacroAssembler::PushTryHandler(CodeLocation try_location,
-                                    HandlerType type) {
+                                    HandlerType type,
+                                    int handler_index) {
   // Adjust this code if not the case.
   STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
-
-  // The pc (return address) is passed in register lr.
+  STATIC_ASSERT(StackHandlerConstants::kCodeOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 4 * kPointerSize);
+
+  // For the JSEntry handler, we must preserve r0-r4, r5-r7 are available.
+  // We will build up the handler from the bottom by pushing on the stack.
+  // First compute the state.
+  unsigned state = StackHandler::OffsetField::encode(handler_index);
   if (try_location == IN_JAVASCRIPT) {
-    if (type == TRY_CATCH_HANDLER) {
-      mov(r3, Operand(StackHandler::TRY_CATCH));
-    } else {
-      mov(r3, Operand(StackHandler::TRY_FINALLY));
-    }
-    stm(db_w, sp, r3.bit() | cp.bit() | fp.bit() | lr.bit());
-    // Save the current handler as the next handler.
-    mov(r3, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
-    ldr(r1, MemOperand(r3));
-    push(r1);
-    // Link this handler as the new current one.
-    str(sp, MemOperand(r3));
+    state |= (type == TRY_CATCH_HANDLER)
+        ? StackHandler::KindField::encode(StackHandler::TRY_CATCH)
+        : StackHandler::KindField::encode(StackHandler::TRY_FINALLY);
   } else {
-    // Must preserve r0-r4, r5-r7 are available.
     ASSERT(try_location == IN_JS_ENTRY);
-    // The frame pointer does not point to a JS frame so we save NULL
-    // for fp. We expect the code throwing an exception to check fp
-    // before dereferencing it to restore the context.
-    mov(r5, Operand(StackHandler::ENTRY));  // State.
-    mov(r6, Operand(Smi::FromInt(0)));  // Indicates no context.
-    mov(r7, Operand(0, RelocInfo::NONE));  // NULL frame pointer.
-    stm(db_w, sp, r5.bit() | r6.bit() | r7.bit() | lr.bit());
-    // Save the current handler as the next handler.
-    mov(r7, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
-    ldr(r6, MemOperand(r7));
-    push(r6);
-    // Link this handler as the new current one.
-    str(sp, MemOperand(r7));
+    state |= StackHandler::KindField::encode(StackHandler::ENTRY);
   }
+
+  // Set up the code object (r5) and the state (r6) for pushing.
+  mov(r5, Operand(CodeObject()));
+  mov(r6, Operand(state));
+
+  // Push the frame pointer, context, state, and code object.
+  if (try_location == IN_JAVASCRIPT) {
+    stm(db_w, sp, r5.bit() | r6.bit() | cp.bit() | fp.bit());
+  } else {
+    mov(r7, Operand(Smi::FromInt(0)));  // Indicates no context.
+    mov(ip, Operand(0, RelocInfo::NONE));  // NULL frame pointer.
+    stm(db_w, sp, r5.bit() | r6.bit() | r7.bit() | ip.bit());
+  }
+
+  // Link the current handler as the next handler.
+  mov(r6, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
+  ldr(r5, MemOperand(r6));
+  push(r5);
+  // Set this new handler as the current one.
+  str(sp, MemOperand(r6));
 }
 
 
@@ -1213,39 +1215,42 @@ void MacroAssembler::PopTryHandler() {
 void MacroAssembler::Throw(Register value) {
   // Adjust this code if not the case.
   STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
-  // r0 is expected to hold the exception.
+  STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0);
+  STATIC_ASSERT(StackHandlerConstants::kCodeOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 4 * kPointerSize);
+
+  // The exception is expected in r0.
   if (!value.is(r0)) {
     mov(r0, value);
   }
-
-  // Drop the sp to the top of the handler.
+  // Drop the stack pointer to the top of the top handler.
   mov(r3, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
   ldr(sp, MemOperand(r3));
-
   // Restore the next handler.
   pop(r2);
   str(r2, MemOperand(r3));
 
-  // Restore context and frame pointer, discard state (r3).
-  ldm(ia_w, sp, r3.bit() | cp.bit() | fp.bit());
+  // Get the code object (r1) and state (r2).  Restore the context and frame
+  // pointer.
+  ldm(ia_w, sp, r1.bit() | r2.bit() | cp.bit() | fp.bit());
 
   // If the handler is a JS frame, restore the context to the frame.
-  // (r3 == ENTRY) == (fp == 0) == (cp == 0), so we could test any
-  // of them.
-  cmp(r3, Operand(StackHandler::ENTRY));
+  // (kind == ENTRY) == (fp == 0) == (cp == 0), so we could test either fp
+  // or cp.
+  tst(cp, cp);
   str(cp, MemOperand(fp, StandardFrameConstants::kContextOffset), ne);
 
-#ifdef DEBUG
-  if (emit_debug_code()) {
-    mov(lr, Operand(pc));
-  }
-#endif
-  pop(pc);
+  // Compute the handler entry address and jump to it.  The handler table is
+  // a fixed array of (smi-tagged) code offsets.
+  // r1 = code object, r2 = state.
+  ldr(r3, FieldMemOperand(r1, Code::kHandlerTableOffset));  // Handler table.
+  add(r3, r3, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  mov(r2, Operand(r2, LSR, StackHandler::kKindWidth));  // Handler index.
+  ldr(r2, MemOperand(r3, r2, LSL, kPointerSizeLog2));  // Smi-tagged offset.
+  add(r1, r1, Operand(Code::kHeaderSize - kHeapObjectTag));  // Code start.
+  add(pc, r1, Operand(r2, ASR, kSmiTagSize));  // Jump.
 }
 
 
@@ -1254,12 +1259,12 @@ void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
   // Adjust this code if not the case.
   STATIC_ASSERT(StackHandlerConstants::kSize == 5 * kPointerSize);
   STATIC_ASSERT(StackHandlerConstants::kNextOffset == 0 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 1 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 2 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 3 * kPointerSize);
-  STATIC_ASSERT(StackHandlerConstants::kPCOffset == 4 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kCodeOffset == 1 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kStateOffset == 2 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kContextOffset == 3 * kPointerSize);
+  STATIC_ASSERT(StackHandlerConstants::kFPOffset == 4 * kPointerSize);
 
-  // The exception is expected in r0.
+  // The exception is expected in eax.

[fschneider, 2011/11/11 09:43:13]

Should be r0 for arm.

[Kevin Millikin (Chromium), 2011/11/11 11:22:50]

Thanks.  Silly that it was right and I changed it :)

   if (type == OUT_OF_MEMORY) {
     // Set external caught exception to false.
     ExternalReference external_caught(Isolate::kExternalCaughtExceptionAddress,
@@ -1282,26 +1287,34 @@ void MacroAssembler::ThrowUncatchable(UncatchableExceptionType type,
   mov(r3, Operand(ExternalReference(Isolate::kHandlerAddress, isolate())));
   ldr(sp, MemOperand(r3));
 
-  // Unwind the handlers until the top ENTRY handler is found.
+  // Unwind the handlers until the ENTRY handler is found.
   Label fetch_next, check_kind;
   jmp(&check_kind);
   bind(&fetch_next);
   ldr(sp, MemOperand(sp, StackHandlerConstants::kNextOffset));
 
   bind(&check_kind);
+  STATIC_ASSERT(StackHandler::ENTRY == 0);
   ldr(r2, MemOperand(sp, StackHandlerConstants::kStateOffset));
-  cmp(r2, Operand(StackHandler::ENTRY));
+  tst(r2, Operand(StackHandler::KindField::kMask));
   b(ne, &fetch_next);
 
   // Set the top handler address to next handler past the top ENTRY handler.
   pop(r2);
   str(r2, MemOperand(r3));
-
-  // Clear the context and frame pointer (0 was saved in the handler), and
-  // discard the state (r2).
-  ldm(ia_w, sp, r2.bit() | cp.bit() | fp.bit());
-
-  pop(pc);
+  // Get the code object (r1) and state (r2).  Clear the context and frame
+  // pointer (0 was saved in the handler).
+  ldm(ia_w, sp, r1.bit() | r2.bit() | cp.bit() | fp.bit());
+
+  // Compute the handler entry address and jump to it.  The handler table is

[Vyacheslav Egorov (Chromium), 2011/11/10 19:01:04]

Seems this code can be shared between throw and throw uncatchable.

[Kevin Millikin (Chromium), 2011/11/11 11:22:50]

Yeah, good idea.  Done.

+  // a fixed array of (smi-tagged) code offsets.
+  // r1 = code object, r2 = state.
+  ldr(r3, FieldMemOperand(r1, Code::kHandlerTableOffset));  // Handler table.
+  add(r3, r3, Operand(FixedArray::kHeaderSize - kHeapObjectTag));
+  mov(r2, Operand(r2, LSR, StackHandler::kKindWidth));  // Handler index.
+  ldr(r2, MemOperand(r3, r2, LSL, kPointerSizeLog2));  // Smi-tagged offset.
+  add(r1, r1, Operand(Code::kHeaderSize - kHeapObjectTag));  // Code start.
+  add(pc, r1, Operand(r2, ASR, kSmiTagSize));  // Jump.
 }