From 813b071b3059081f42bd85ee3078b4d677a0eb14 Mon Sep 17 00:00:00 2001
From: "weiliang.lin@intel.com" <weiliang.lin@intel.com>
Date: Wed, 5 Nov 2014 06:20:36 +0000
Subject: [PATCH] Set the FPU precision control to double-precision.

The default double precision control of FPU is extended double-precision.
While the number definition for JavaScript is double-precision. We use
the FPU control word to set the doulbe precision and replace the original
solution which store the data to memory and load it again.

This patch also fixes the error that Sunspider 1.0.2 can not run with V8 if
sse2 support is disabled.

BUG=
R=weiliang.lin@intel.com

Review URL: https://codereview.chromium.org/700053003

Patch from Chunyang Dai <chunyang.dai@intel.com>.

Cr-Commit-Position: refs/heads/master@{#25125}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25125 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 src/x87/lithium-codegen-x87.cc | 10 ++++------
 src/x87/macro-assembler-x87.cc |  7 +++++++
 src/x87/macro-assembler-x87.h  |  1 +
 3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/x87/lithium-codegen-x87.cc b/src/x87/lithium-codegen-x87.cc
index 2766b658f..f8872d718 100644
--- a/src/x87/lithium-codegen-x87.cc
+++ b/src/x87/lithium-codegen-x87.cc
@@ -2272,6 +2272,8 @@ void LCodeGen::DoArithmeticD(LArithmeticD* instr) {
   if (instr->op() != Token::MOD) {
     X87PrepareBinaryOp(left, right, result);
   }
+  // Set the precision control to double-precision.
+  __ X87SetFPUCW(0x027F);
   switch (instr->op()) {
     case Token::ADD:
       __ fadd_i(1);
@@ -2306,12 +2308,8 @@ void LCodeGen::DoArithmeticD(LArithmeticD* instr) {
       break;
   }
 
-  // Only always explicitly storing to memory to force the round-down for double
-  // arithmetic.
-  __ lea(esp, Operand(esp, -kDoubleSize));
-  __ fstp_d(Operand(esp, 0));
-  __ fld_d(Operand(esp, 0));
-  __ lea(esp, Operand(esp, kDoubleSize));
+  // Restore the default value of control word.
+  __ X87SetFPUCW(0x037F);
 }
 
 
diff --git a/src/x87/macro-assembler-x87.cc b/src/x87/macro-assembler-x87.cc
index ff5db7bdb..3f522fcb1 100644
--- a/src/x87/macro-assembler-x87.cc
+++ b/src/x87/macro-assembler-x87.cc
@@ -767,6 +767,13 @@ void MacroAssembler::X87SetRC(int rc) {
 }
 
 
+void MacroAssembler::X87SetFPUCW(int cw) {
+  push(Immediate(cw));
+  fldcw(MemOperand(esp, 0));
+  add(esp, Immediate(kPointerSize));
+}
+
+
 void MacroAssembler::AssertNumber(Register object) {
   if (emit_debug_code()) {
     Label ok;
diff --git a/src/x87/macro-assembler-x87.h b/src/x87/macro-assembler-x87.h
index 07964562b..ad308a495 100644
--- a/src/x87/macro-assembler-x87.h
+++ b/src/x87/macro-assembler-x87.h
@@ -425,6 +425,7 @@ class MacroAssembler: public Assembler {
   void FXamSign();
   void X87CheckIA();
   void X87SetRC(int rc);
+  void X87SetFPUCW(int cw);
 
   void ClampUint8(Register reg);
   void ClampTOSToUint8(Register result_reg);
-- 
2.34.1