ARM: Implement sqrt in inline assembly.

Call VSQRT directly to avoid the tiniest (1ulp) precision
error that occurs in the system-supplied sqrt on QNX/ARM.

All precision tests in SunSpider are now passing on this platform.

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/98363010

Patch from Cosmin Truta <ctruta@gmail.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18506 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/codegen-arm.cc

@@ -347,13 +347,33 @@ OS::MemCopyUint16Uint8Function CreateMemCopyUint16Uint8Function(
 }
 #endif
 
-#undef __
-
-
 UnaryMathFunction CreateSqrtFunction() {
-  return &sqrt;
+#if defined(USE_SIMULATOR)
+  return &std::sqrt;
+#else
+  size_t actual_size;
+  byte* buffer = static_cast<byte*>(OS::Allocate(1 * KB, &actual_size, true));
+  if (buffer == NULL) return &std::sqrt;
+
+  MacroAssembler masm(NULL, buffer, static_cast<int>(actual_size));
+
+  __ GetCFunctionDoubleResult(d0);
+  __ vsqrt(d0, d0);
+  __ SetCallCDoubleArguments(d0);
+  __ Ret();
+
+  CodeDesc desc;
+  masm.GetCode(&desc);
+  ASSERT(!RelocInfo::RequiresRelocation(desc));
+
+  CPU::FlushICache(buffer, actual_size);
+  OS::ProtectCode(buffer, actual_size);
+  return FUNCTION_CAST<UnaryMathFunction>(buffer);
+#endif
 }
 
+#undef __
+
 
 // -------------------------------------------------------------------------
 // Platform-specific RuntimeCallHelper functions.