From d905cbfd5d05b7c22ae6a28fd27208f0aa53e3d2 Mon Sep 17 00:00:00 2001
From: magumagu <magumagu9@gmail.com>
Date: Sat, 14 Jun 2014 21:22:34 -0700
Subject: [PATCH] Don't set DAZ on x86 in non-IEEE mode.

I have no idea why we were using it in the first place; it doesn't match
the behavior of PPC NI flag.
---
 Source/Core/Common/CPUDetect.h         |  1 -
 Source/Core/Common/x64CPUDetect.cpp    | 29 +++-----------------------
 Source/Core/Common/x64FPURoundMode.cpp | 11 +---------
 Source/Core/Core/Core.cpp              |  4 ----
 4 files changed, 4 insertions(+), 41 deletions(-)

diff --git a/Source/Core/Common/CPUDetect.h b/Source/Core/Common/CPUDetect.h
index e5feb20f88..38cfa4be17 100644
--- a/Source/Core/Common/CPUDetect.h
+++ b/Source/Core/Common/CPUDetect.h
@@ -77,7 +77,6 @@ struct CPUInfo
 
 	// Turn the cpu info into a string we can show
 	std::string Summarize();
-	bool IsUnsafe();
 
 private:
 	// Detects the various cpu features
diff --git a/Source/Core/Common/x64CPUDetect.cpp b/Source/Core/Common/x64CPUDetect.cpp
index e64cd9d1ee..8340344481 100644
--- a/Source/Core/Common/x64CPUDetect.cpp
+++ b/Source/Core/Common/x64CPUDetect.cpp
@@ -162,32 +162,10 @@ void CPUInfo::Detect()
 		if ((cpu_id[2] >> 22) & 1) bMOVBE = true;
 		if ((cpu_id[2] >> 25) & 1) bAES = true;
 
-		// To check DAZ support, we first need to check FXSAVE support.
 		if ((cpu_id[3] >> 24) & 1)
 		{
 			// We can use FXSAVE.
 			bFXSR = true;
-
-			GC_ALIGNED16(u8 fx_state[512]);
-			memset(fx_state, 0, sizeof(fx_state));
-#ifdef _WIN32
-#if _M_X86_32
-			_fxsave(fx_state);
-#elif _M_X86_64
-			_fxsave64(fx_state);
-#endif
-#else
-			__asm__("fxsave %0" : "=m" (fx_state));
-#endif
-
-			// lowest byte of MXCSR_MASK
-			if ((fx_state[0x1C] >> 6) & 1)
-			{
-				// On x86, the FTZ field (supported since SSE1) only flushes denormal _outputs_ to zero,
-				// now that we checked DAZ support (flushing denormal _inputs_ to zero),
-				// we can set our generic flag.
-				bFlushToZero = true;
-			}
 		}
 
 		// AVX support requires 3 separate checks:
@@ -204,6 +182,9 @@ void CPUInfo::Detect()
 			}
 		}
 	}
+
+	bFlushToZero = bSSE;
+
 	if (max_ex_fn >= 0x80000004) {
 		// Extract brand string
 		__cpuid(cpu_id, 0x80000002);
@@ -269,7 +250,3 @@ std::string CPUInfo::Summarize()
 	return sum;
 }
 
-bool CPUInfo::IsUnsafe()
-{
-	return !bFlushToZero;
-}
diff --git a/Source/Core/Common/x64FPURoundMode.cpp b/Source/Core/Common/x64FPURoundMode.cpp
index 403473ab1a..83b50ddb63 100644
--- a/Source/Core/Common/x64FPURoundMode.cpp
+++ b/Source/Core/Common/x64FPURoundMode.cpp
@@ -62,8 +62,6 @@ namespace FPURoundMode
 	{
 		// OR-mask for disabling FPU exceptions (bits 7-12 in the MXCSR register)
 		const u32 EXCEPTION_MASK = 0x1F80;
-		// Denormals-Are-Zero (non-IEEE mode: denormal inputs are set to +/- 0)
-		const u32 DAZ = 0x40;
 		// Flush-To-Zero (non-IEEE mode: denormal outputs are set to +/- 0)
 		const u32 FTZ = 0x8000;
 		// lookup table for FPSCR.RN-to-MXCSR.RC translation
@@ -76,16 +74,9 @@ namespace FPURoundMode
 		};
 		u32 csr = simd_rounding_table[rounding_mode];
 
-		// Some initial steppings of Pentium 4 CPUs support FTZ but not DAZ.
-		// They will not flush input operands but flushing outputs only is better than nothing.
-		static const u32 denormalLUT[2] =
-		{
-			FTZ,       // flush-to-zero only
-			FTZ | DAZ, // flush-to-zero and denormals-are-zero (may not be supported)
-		};
 		if (non_ieee_mode)
 		{
-			csr |= denormalLUT[cpu_info.bFlushToZero];
+			csr |= FTZ;
 		}
 		_mm_setcsr(csr);
 	}
diff --git a/Source/Core/Core/Core.cpp b/Source/Core/Core/Core.cpp
index 5e5dc7318c..c6e1bc64ac 100644
--- a/Source/Core/Core/Core.cpp
+++ b/Source/Core/Core/Core.cpp
@@ -379,10 +379,6 @@ void EmuThread()
 	DisplayMessage(cpu_info.brand_string, 8000);
 	DisplayMessage(cpu_info.Summarize(), 8000);
 	DisplayMessage(_CoreParameter.m_strFilename, 3000);
-	if (cpu_info.IsUnsafe() && (NetPlay::IsNetPlayRunning() || Movie::IsRecordingInput() || Movie::IsPlayingInput()))
-	{
-		PanicAlertT("Warning: Netplay/movies will desync because your CPU does not support DAZ and Dolphin does not emulate it anymore.");
-	}
 
 	Movie::Init();