From 94c18b1cf8be72b4775efc0a64d87da056b8fdd9 Mon Sep 17 00:00:00 2001
From: "ricow@chromium.org"
 <ricow@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Mon, 28 Feb 2011 13:57:42 +0000
Subject: [PATCH] X64: Add a jumptable to for deoptimization checks on X64.

The current version includes an extra jump compared to IA32, because
we need to load the jump address into a register and do an indirect
jump, but in the normal case we just jump over this by negating the
deoptimization conditional.

Review URL: http://codereview.chromium.org/6596032

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6972 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/x64/lithium-codegen-x64.cc | 26 ++++++++++++++++++++++----
 src/x64/lithium-codegen-x64.h  | 11 +++++++++++
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index 90244f1..555908c 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -77,6 +77,7 @@ bool LCodeGen::GenerateCode() {
   return GeneratePrologue() &&
       GenerateBody() &&
       GenerateDeferredCode() &&
+      GenerateJumpTable() &&
       GenerateSafepointTable();
 }
 
@@ -240,6 +241,16 @@ LInstruction* LCodeGen::GetNextInstruction() {
 }
 
 
+bool LCodeGen::GenerateJumpTable() {
+  for (int i = 0; i < jump_table_.length(); i++) {
+    JumpTableEntry* info = jump_table_[i];
+    __ bind(&(info->label_));
+    __ Jump(info->address_, RelocInfo::RUNTIME_ENTRY);
+  }
+  return !is_aborted();
+}
+
+
 bool LCodeGen::GenerateDeferredCode() {
   ASSERT(is_generating());
   for (int i = 0; !is_aborted() && i < deferred_.length(); i++) {
@@ -512,10 +523,17 @@ void LCodeGen::DeoptimizeIf(Condition cc, LEnvironment* environment) {
   if (cc == no_condition) {
     __ Jump(entry, RelocInfo::RUNTIME_ENTRY);
   } else {
-    NearLabel done;
-    __ j(NegateCondition(cc), &done);
-    __ Jump(entry, RelocInfo::RUNTIME_ENTRY);
-    __ bind(&done);
+    JumpTableEntry* jump_info = NULL;
+    // We often have several deopts to the same entry, reuse the last
+    // jump entry if this is the case.
+    if (jump_table_.length() > 0 &&
+        jump_table_[jump_table_.length() - 1]->address_ == entry) {
+      jump_info = jump_table_[jump_table_.length() - 1];
+    } else {
+      jump_info = new JumpTableEntry(entry);
+      jump_table_.Add(jump_info);
+    }
+    __ j(cc, &jump_info->label_);
   }
 }
 
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index 1cac4e9..420556a 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -53,6 +53,7 @@ class LCodeGen BASE_EMBEDDED {
         current_instruction_(-1),
         instructions_(chunk->instructions()),
         deoptimizations_(4),
+        jump_table_(4),
         deoptimization_literals_(8),
         inlined_function_count_(0),
         scope_(chunk->graph()->info()->scope()),
@@ -147,6 +148,7 @@ class LCodeGen BASE_EMBEDDED {
   bool GeneratePrologue();
   bool GenerateBody();
   bool GenerateDeferredCode();
+  bool GenerateJumpTable();
   bool GenerateSafepointTable();
 
   void CallCode(Handle<Code> code,
@@ -234,6 +236,14 @@ class LCodeGen BASE_EMBEDDED {
   // Emits code for pushing a constant operand.
   void EmitPushConstantOperand(LOperand* operand);
 
+  struct JumpTableEntry {
+    inline JumpTableEntry(Address address)
+        : label_(),
+          address_(address) { }
+    Label label_;
+    Address address_;
+  };
+
   LChunk* const chunk_;
   MacroAssembler* const masm_;
   CompilationInfo* const info_;
@@ -242,6 +252,7 @@ class LCodeGen BASE_EMBEDDED {
   int current_instruction_;
   const ZoneList<LInstruction*>* instructions_;
   ZoneList<LEnvironment*> deoptimizations_;
+  ZoneList<JumpTableEntry*> jump_table_;
   ZoneList<Handle<Object> > deoptimization_literals_;
   int inlined_function_count_;
   Scope* const scope_;
-- 
2.7.4