Set default rounding mode to FE_NEAREST again. Thanks to Matthias Bentrup for providing some explanations.

code/asm/ftola.asm

@@ -25,11 +25,11 @@ IFNDEF idx64
 .model flat, c
 ENDIF
 
-; .data
+.data
 
-; ifndef idx64
-;   fpucw WORD 0F7Fh
-; endif
+ifndef idx64
+  fpucw WORD 0F7Fh
+endif
 
 .code
 
@@ -51,22 +51,19 @@ ELSE
 ; qftol using FPU
 
   qftolx87m macro src
-;    not necessary, fpucw is set with _controlfp at startup
-;    sub esp, 2
-;    fnstcw word ptr [esp]
-;    fldcw fpucw
+    sub esp, 2
+    fnstcw word ptr [esp]
+    fldcw fpucw
     fld dword ptr src
 	fistp dword ptr src
-;	fldcw [esp]
+	fldcw [esp]
 	mov eax, src
-;	add esp, 2
+	add esp, 2
 	ret
   endm
   
   qftolx87 PROC
-; need this line when storing FPU control word on stack
-;    qftolx87m [esp + 6]
-    qftolx87m [esp + 4]
+    qftolx87m [esp + 6]
   qftolx87 ENDP
 
   qvmftolx87 PROC

code/asm/ftola.c

@@ -22,6 +22,8 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
 #include "qasm-inline.h"
 
+static const unsigned short fpucw = 0x0C7F;
+
 /*
  * GNU inline asm ftol conversion functions using SSE or FPU
  */
@@ -59,14 +61,18 @@ int qvmftolsse(void)
 long qftolx87(float f)
 {
   long retval;
+  unsigned short oldcw;
 
   __asm__ volatile
   (
+    "fnstcw %2\n"
+    "fldcw %3\n"
     "flds %1\n"
     "fistpl %1\n"
+    "fldcw %2\n"
     "mov %1, %0\n"
     : "=r" (retval)
-    : "m" (f)
+    : "m" (f), "m" (oldcw), "m" (fpucw)
   );
   
   return retval;
@@ -75,13 +81,18 @@ long qftolx87(float f)
 int qvmftolx87(void)
 {
   int retval;
+  unsigned short oldcw;
 
   __asm__ volatile
   (
+    "fnstcw %1\n"
+    "fldcw %2\n"
     "flds (" EDI ", " EBX ", 4)\n"
     "fistpl (" EDI ", " EBX ", 4)\n"
+    "fldcw %2\n"
     "mov (" EDI ", " EBX ", 4), %0\n"
     : "=r" (retval)
+    : "m" (oldcw), "m" (fpucw)
   );
   
   return retval;

code/asm/snapvector.asm

@@ -45,9 +45,6 @@ IFDEF idx64
 
   qsnapvectorsse PROC
     sub rsp, 8
-	stmxcsr [rsp]				; save SSE control word
-	ldmxcsr ssecw				; set to round nearest
-
 	movaps xmm1, ssemask		; initialize the mask register
 	movups xmm0, [rcx]			; here is stored our vector. Read 4 values in one go
 	movaps xmm2, xmm0			; keep a copy of the original data
@@ -57,20 +54,13 @@ IFDEF idx64
 	cvtdq2ps xmm0, xmm0			; convert 4 int to single fp
 	orps xmm0, xmm1				; combine all 4 values again
 	movups [rcx], xmm0			; write 3 rounded and 1 unchanged values back to memory
-
-	ldmxcsr [rsp]				; restore sse control word to old value
-	add rsp, 8
 	ret
   qsnapvectorsse ENDP
 
 ELSE
 
   qsnapvectorsse PROC
-	sub esp, 8
-	stmxcsr [esp]				; save SSE control word
-	ldmxcsr ssecw				; set to round nearest
-
-	mov eax, dword ptr 12[esp]		; store address of vector in eax
+	mov eax, dword ptr 4[esp]		; store address of vector in eax
 	movaps xmm1, ssemask			; initialize the mask register for maskmovdqu
 	movups xmm0, [eax]			; here is stored our vector. Read 4 values in one go
 	movaps xmm2, xmm0			; keep a copy of the original data
@@ -80,9 +70,6 @@ ELSE
 	cvtdq2ps xmm0, xmm0			; convert 4 int to single fp
 	orps xmm0, xmm1				; combine all 4 values again
 	movups [eax], xmm0			; write 3 rounded and 1 unchanged values back to memory
-
-	ldmxcsr [esp]				; restore sse control word to old value
-	add esp, 8
 	ret
   qsnapvectorsse ENDP
 
@@ -95,14 +82,9 @@ ELSE
 
   qsnapvectorx87 PROC
 	mov eax, dword ptr 4[esp]
-	sub esp, 2
-	fnstcw word ptr [esp]
-	fldcw fpucw
 	qroundx87 [eax]
 	qroundx87 4[eax]
 	qroundx87 8[eax]
-	fldcw [esp]
-	add esp, 2
 	ret
   qsnapvectorx87 ENDP
 

code/asm/snapvector.c

@@ -33,31 +33,21 @@ static unsigned char ssemask[16] __attribute__((aligned(16))) =
 	"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x00\x00\x00\x00"
 };
 
-static const unsigned int ssecw __attribute__((aligned(16))) = 0x00001F80;
-static const unsigned short fpucw = 0x037F;
-
 void qsnapvectorsse(vec3_t vec)
 {
-	uint32_t oldcw __attribute__((aligned(16)));
-	
 	__asm__ volatile
 	(
-		"stmxcsr %3\n"
-		"ldmxcsr %1\n"
-
 		"movaps (%0), %%xmm1\n"
-		"movups (%2), %%xmm0\n"
+		"movups (%1), %%xmm0\n"
 		"movaps %%xmm0, %%xmm2\n"
 		"andps %%xmm1, %%xmm0\n"
 		"andnps %%xmm2, %%xmm1\n"
 		"cvtps2dq %%xmm0, %%xmm0\n"
 		"cvtdq2ps %%xmm0, %%xmm0\n"
 		"orps %%xmm1, %%xmm0\n"
-		"movups %%xmm0, (%2)\n"
-		
-		"ldmxcsr %3\n"
+		"movups %%xmm0, (%1)\n"
 		:
-		: "r" (ssemask), "m" (ssecw), "r" (vec), "m" (oldcw)
+		: "r" (ssemask), "r" (vec)
 		: "memory", "%xmm0", "%xmm1", "%xmm2"
 	);
 	
@@ -73,16 +63,11 @@ void qsnapvectorx87(vec3_t vec)
 {
 	__asm__ volatile
 	(
-		"sub $2, " ESP "\n"
-		"fnstcw (" ESP ")\n"
-		"fldcw %0\n"
-		QROUNDX87("(%1)")
-		QROUNDX87("4(%1)")
-		QROUNDX87("8(%1)")
-		"fldcw (" ESP ")\n"
-		"add $2, " ESP "\n"
+		QROUNDX87("(%0)")
+		QROUNDX87("4(%0)")
+		QROUNDX87("8(%0)")
 		:
-		: "m" (fpucw), "r" (vec)
+		: "r" (vec)
 		: "memory"
 	);
 }

code/sys/sys_unix.c

@@ -810,8 +810,8 @@ void Sys_GLimpInit( void )
 
 void Sys_SetFloatEnv(void)
 {
-	// rounding towards 0
-	fesetround(FE_TOWARDZERO);
+	// rounding toward nearest
+	fesetround(FE_TONEAREST);
 }
 
 /*

code/sys/sys_win32.c

@@ -59,14 +59,14 @@ Set FPU control word to default value
   #define _MCW_EM	0x0008001fU
   #define _MCW_RC	0x00000300U
   #define _MCW_PC	0x00030000U
-  #define _RC_CHOP	0x00000300U
+  #define _RC_NEAR      0x00000000U
   #define _PC_53	0x00010000U
   
   unsigned int _controlfp(unsigned int new, unsigned int mask);
 #endif
 
 #define FPUCWMASK1 (_MCW_RC | _MCW_EM)
-#define FPUCW (_RC_CHOP | _MCW_EM | _PC_53)
+#define FPUCW (_RC_NEAR | _MCW_EM | _PC_53)
 
 #if idx64
 #define FPUCWMASK	(FPUCWMASK1)