Small change to stack checks in unoptimized code.

The stack checks include a loop nesting depth encoded in the code stream
after the call to the stack check stub.  Change the code to jump around this
instruction as well as the call when the stack check is OK.

Review URL: http://codereview.chromium.org/6005014

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@6204 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/full-codegen-arm.cc

-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -221,10 +221,17 @@ void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
   __ b(hs, &ok);
   StackCheckStub stub;
   __ CallStub(&stub);
+  // Record a mapping of this PC offset to the OSR id.  This is used to find
+  // the AST id from the unoptimized code in order to use it as a key into
+  // the deoptimization input data found in the optimized code.
+  RecordStackCheck(stmt->OsrEntryId());
+
   __ bind(&ok);
   PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
+  // Record a mapping of the OSR id to this PC.  This is used if the OSR
+  // entry becomes the target of a bailout.  We don't expect it to be, but
+  // we want it to work if it is.
   PrepareForBailoutForId(stmt->OsrEntryId(), NO_REGISTERS);
-  RecordStackCheck(stmt->OsrEntryId());
 }
 
 

src/ia32/deoptimizer-ia32.cc

-// Copyright 2010 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
@@ -105,23 +105,25 @@ void Deoptimizer::DeoptimizeFunction(JSFunction* function) {
 
 void Deoptimizer::PatchStackCheckCode(RelocInfo* rinfo,
                                       Code* replacement_code) {
-  // The stack check code matches the pattern (on ia32, for example):
+  // The stack check code matches the pattern:
   //
   //     cmp esp, <limit>
   //     jae ok
   //     call <stack guard>
+  //     test eax, <loop nesting depth>
   // ok: ...
   //
-  // We will patch the code to:
+  // We will patch away the branch so the code is:
   //
   //     cmp esp, <limit>  ;; Not changed
   //     nop
   //     nop
   //     call <on-stack replacment>
+  //     test eax, <loop nesting depth>
   // ok:
   Address call_target_address = rinfo->pc();
   ASSERT(*(call_target_address - 3) == 0x73 &&  // jae
-         *(call_target_address - 2) == 0x05 &&  // offset
+         *(call_target_address - 2) == 0x07 &&  // offset
          *(call_target_address - 1) == 0xe8);   // call
   *(call_target_address - 3) = 0x90;  // nop
   *(call_target_address - 2) = 0x90;  // nop
@@ -130,12 +132,14 @@ void Deoptimizer::PatchStackCheckCode(RelocInfo* rinfo,
 
 
 void Deoptimizer::RevertStackCheckCode(RelocInfo* rinfo, Code* check_code) {
+  // Replace the nops from patching (Deoptimizer::PatchStackCheckCode) to
+  // restore the conditional branch.
   Address call_target_address = rinfo->pc();
   ASSERT(*(call_target_address - 3) == 0x90 &&  // nop
          *(call_target_address - 2) == 0x90 &&  // nop
          *(call_target_address - 1) == 0xe8);   // call
   *(call_target_address - 3) = 0x73;  // jae
-  *(call_target_address - 2) = 0x05;  // offset
+  *(call_target_address - 2) = 0x07;  // offset
   rinfo->set_target_address(check_code->entry());
 }
 

src/ia32/full-codegen-ia32.cc

@@ -264,16 +264,24 @@ void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
   __ j(above_equal, &ok, taken);
   StackCheckStub stub;
   __ CallStub(&stub);
-  __ bind(&ok);
-  PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
-  PrepareForBailoutForId(stmt->OsrEntryId(), NO_REGISTERS);
+  // Record a mapping of this PC offset to the OSR id.  This is used to find
+  // the AST id from the unoptimized code in order to use it as a key into
+  // the deoptimization input data found in the optimized code.
   RecordStackCheck(stmt->OsrEntryId());
-  // Loop stack checks can be patched to perform on-stack
-  // replacement. In order to decide whether or not to perform OSR we
-  // embed the loop depth in a test instruction after the call so we
-  // can extract it from the OSR builtin.
+
+  // Loop stack checks can be patched to perform on-stack replacement. In
+  // order to decide whether or not to perform OSR we embed the loop depth
+  // in a test instruction after the call so we can extract it from the OSR
+  // builtin.
   ASSERT(loop_depth() > 0);
   __ test(eax, Immediate(Min(loop_depth(), Code::kMaxLoopNestingMarker)));
+
+  __ bind(&ok);
+  PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
+  // Record a mapping of the OSR id to this PC.  This is used if the OSR
+  // entry becomes the target of a bailout.  We don't expect it to be, but
+  // we want it to work if it is.
+  PrepareForBailoutForId(stmt->OsrEntryId(), NO_REGISTERS);
 }
 
 

src/x64/full-codegen-x64.cc

@@ -210,10 +210,17 @@ void FullCodeGenerator::EmitStackCheck(IterationStatement* stmt) {
   __ j(above_equal, &ok);
   StackCheckStub stub;
   __ CallStub(&stub);
+  // Record a mapping of this PC offset to the OSR id.  This is used to find
+  // the AST id from the unoptimized code in order to use it as a key into
+  // the deoptimization input data found in the optimized code.
+  RecordStackCheck(stmt->OsrEntryId());
+
   __ bind(&ok);
   PrepareForBailoutForId(stmt->EntryId(), NO_REGISTERS);
+  // Record a mapping of the OSR id to this PC.  This is used if the OSR
+  // entry becomes the target of a bailout.  We don't expect it to be, but
+  // we want it to work if it is.
   PrepareForBailoutForId(stmt->OsrEntryId(), NO_REGISTERS);
-  RecordStackCheck(stmt->OsrEntryId());
 }