Experimental: fix two issues with ARM fast (jump table) switches....

src/codegen-arm.cc

Index: src/codegen-arm.cc
===================================================================
--- src/codegen-arm.cc	(revision 1339)
+++ src/codegen-arm.cc	(working copy)
@@ -1448,18 +1448,25 @@
     Vector<Label*> case_targets,
     Vector<Label> case_labels) {
   VirtualFrame::SpilledScope spilled_scope(this);
+  JumpTarget setup_default(this);
+  JumpTarget is_smi(this);
+
+  // A non-null default label pointer indicates a default case among
+  // the case labels.  Otherwise we use the break target as a
+  // "default".
+  JumpTarget* default_target =
+      (default_label == NULL) ? node->break_target() : &setup_default;
+
   ASSERT(kSmiTag == 0 && kSmiTagSize <= 2);
-
   frame_->EmitPop(r0);
 
   // Test for a Smi value in a HeapNumber.
-  JumpTarget is_smi(this);
   __ tst(r0, Operand(kSmiTagMask));
   is_smi.Branch(eq);
   __ ldr(r1, MemOperand(r0, HeapObject::kMapOffset - kHeapObjectTag));
   __ ldrb(r1, MemOperand(r1, Map::kInstanceTypeOffset - kHeapObjectTag));
   __ cmp(r1, Operand(HEAP_NUMBER_TYPE));
-  __ b(ne, default_label);
+  default_target->Branch(ne);
   frame_->EmitPush(r0);
   frame_->CallRuntime(Runtime::kNumberToSmi, 1);
   is_smi.Bind();
@@ -1479,17 +1486,25 @@
     }
   }
   __ tst(r0, Operand(0x80000000 | kSmiTagMask));
-  __ b(ne, default_label);
+  default_target->Branch(ne);
   __ cmp(r0, Operand(Smi::FromInt(range)));
-  __ b(ge, default_label);
+  default_target->Branch(ge);
+  VirtualFrame* start_frame = new VirtualFrame(frame_);
   __ SmiJumpTable(r0, case_targets);
 
-  VirtualFrame* start_frame = new VirtualFrame(frame_);
-  // Table containing branch operations.
-  for (int i = 0; i < range; i++) {
-    __ jmp(case_targets[i]);
+  GenerateFastCaseSwitchCases(node, case_labels, start_frame);
+
+  // If there was a default case, we need to emit the code to match
+  // it.

[Lasse Reichstein, 2009/02/24 11:55:06]

This comment should be more descriptive.

[Kevin Millikin (Chromium), 2009/02/24 12:33:19]

Descriptified.

+  if (default_label != NULL) {
+    node->break_target()->Jump();
+    setup_default.Bind();
+    frame_->MergeTo(start_frame);
+    __ b(default_label);
+    DeleteFrame();
   }
-  GenerateFastCaseSwitchCases(node, case_labels, start_frame);
+  node->break_target()->Bind();
+
   delete start_frame;
 }