From ab041ee4ed34bc10d1781159b4a754c8affdf5d6 Mon Sep 17 00:00:00 2001
From: "whesse@chromium.org"
 <whesse@chromium.org@ce2b1a6d-e550-0410-aec6-3dcde31c8c00>
Date: Mon, 17 Aug 2009 08:02:07 +0000
Subject: [PATCH] X64: Do not use an AllocateWithoutSpill register if it is
 invalid.  Abandoned in favor of approach in
 http://codereview.chromium.org/165525/show (Issue 165526) Review URL:
 http://codereview.chromium.org/164480

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2693 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/x64/codegen-x64.cc | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/src/x64/codegen-x64.cc b/src/x64/codegen-x64.cc
index b3df929d78..8ed9817cd6 100644
--- a/src/x64/codegen-x64.cc
+++ b/src/x64/codegen-x64.cc
@@ -3084,26 +3084,36 @@ void CodeGenerator::VisitCountOperation(CountOperation* node) {
                                                   is_increment);
     }
 
+    // If we have a free register, combine the smi and overflow checks.
     Result tmp = allocator_->AllocateWithoutSpilling();
     ASSERT(kSmiTagMask == 1 && kSmiTag == 0);
-    __ movl(tmp.reg(), Immediate(kSmiTagMask));
-    // Smi test.
+    if (tmp.is_valid()) {
+      __ movl(tmp.reg(), Immediate(kSmiTagMask));
+    }
+
+    // Try incrementing or decrementing the smi.
     __ movq(kScratchRegister, new_value.reg());
     if (is_increment) {
       __ addl(kScratchRegister, Immediate(Smi::FromInt(1)));
     } else {
       __ subl(kScratchRegister, Immediate(Smi::FromInt(1)));
     }
-    // deferred->Branch(overflow);
-    __ cmovl(overflow, kScratchRegister, tmp.reg());
-    __ testl(kScratchRegister, tmp.reg());
-    tmp.Unuse();
-    deferred->Branch(not_zero);
+
+    // Go to the deferred case if the result overflows or is non-smi.
+    if (tmp.is_valid()){
+      __ cmovl(overflow, kScratchRegister, tmp.reg());
+      __ testl(kScratchRegister, tmp.reg());
+      tmp.Unuse();
+      deferred->Branch(not_zero);
+    } else {
+      deferred->Branch(overflow);
+      __ testl(kScratchRegister, Immediate(kSmiTagMask));
+      deferred->Branch(not_zero);
+    }
+
     __ movq(new_value.reg(), kScratchRegister);
-
     deferred->BindExit();
 
-
     // Postfix: store the old value in the allocated slot under the
     // reference.
     if (is_postfix) frame_->SetElementAt(target.size(), &old_value);