X87: Fix the sqrt precision issue.

  In order to resolve the sqrt precision issue described in https://codereview.chromium.org/1425763002/.
  we change the implementation of CreateSqrtFunction() implementation of X87 so that the optimize compiler
  and full-compiler implementation are unified.

R=weiliang.lin@intel.com
BUG=

Review URL: https://codereview.chromium.org/1417553007

Cr-Commit-Position: refs/heads/master@{#31625}

src/compiler/x87/code-generator-x87.cc

@@ -972,24 +972,12 @@ void CodeGenerator::AssembleArchInstruction(Instruction* instr) {
       break;
     }
     case kX87Float64Sqrt: {
+      __ X87SetFPUCW(0x027F);
       __ fstp(0);
       __ fld_d(MemOperand(esp, 0));
-#if V8_GLIBC_PREREQ(2, 19)
-      __ push(edx);
-      __ sub(esp, Immediate(2 * kIntSize));
-      __ fnstcw(MemOperand(esp, 4));
-      __ mov(edx, Immediate(0xfeff));
-      __ and_(edx, MemOperand(esp, 4));
-      __ mov(MemOperand(esp, 0), edx);
-      __ fldcw(MemOperand(esp, 0));
-#endif
       __ fsqrt();
-#if V8_GLIBC_PREREQ(2, 19)
-      __ fldcw(MemOperand(esp, 4));
-      __ lea(esp, Operand(esp, 2 * kIntSize));
-      __ pop(edx);
-#endif
       __ lea(esp, Operand(esp, kDoubleSize));
+      __ X87SetFPUCW(0x037F);
       break;
     }
     case kX87Float64Round: {

src/x87/codegen-x87.cc

@@ -41,8 +41,27 @@ UnaryMathFunction CreateExpFunction() {
 
 
 UnaryMathFunction CreateSqrtFunction() {
-  // No SSE2 support
-  return &std::sqrt;
+  size_t actual_size;
+  // Allocate buffer in executable space.
+  byte* buffer =
+      static_cast<byte*>(base::OS::Allocate(1 * KB, &actual_size, true));
+  if (buffer == NULL) return &std::sqrt;
+
+  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));
+  // Load double input into registers.
+  __ fld_d(MemOperand(esp, 4));
+  __ X87SetFPUCW(0x027F);
+  __ fsqrt();
+  __ X87SetFPUCW(0x037F);
+  __ Ret();
+
+  CodeDesc desc;
+  masm.GetCode(&desc);
+  DCHECK(!RelocInfo::RequiresRelocation(desc));
+
+  Assembler::FlushICacheWithoutIsolate(buffer, actual_size);
+  base::OS::ProtectCode(buffer, actual_size);
+  return FUNCTION_CAST<UnaryMathFunction>(buffer);
 }