From 4424f6ba9a59b06c10d0bb683c8e00cded1d90db Mon Sep 17 00:00:00 2001
From: tertu marybig <flameshadowxeroshin@gmail.com>
Date: Tue, 28 Sep 2021 08:31:14 -0500
Subject: [PATCH] Remove FixedMul and FixedDiv2 asm implementations Actually
 works this time

---
 src/m_fixed.c |  44 ----------------
 src/m_fixed.h | 136 ++++++++------------------------------------------
 2 files changed, 22 insertions(+), 158 deletions(-)

diff --git a/src/m_fixed.c b/src/m_fixed.c
index d40ccd98e..315ac0bde 100644
--- a/src/m_fixed.c
+++ b/src/m_fixed.c
@@ -21,50 +21,6 @@
 #include "doomdef.h"
 #include "m_fixed.h"
 
-#ifdef __USE_C_FIXEDMUL__
-
-/**	\brief	The FixedMul function
-
-	\param	a	fixed_t number
-	\param	b	fixed_t number
-
-	\return	a*b>>FRACBITS
-
-*/
-fixed_t FixedMul(fixed_t a, fixed_t b)
-{
-	// Need to cast to unsigned before shifting to avoid undefined behaviour
-	// for negative integers
-	return (fixed_t)(((UINT64)((INT64)a * b)) >> FRACBITS);
-}
-
-#endif //__USE_C_FIXEDMUL__
-
-#ifdef __USE_C_FIXEDDIV__
-/**	\brief	The FixedDiv2 function
-
-	\param	a	fixed_t number
-	\param	b	fixed_t number
-
-	\return	a/b * FRACUNIT
-
-*/
-fixed_t FixedDiv2(fixed_t a, fixed_t b)
-{
-	INT64 ret;
-
-	if (b == 0)
-		I_Error("FixedDiv: divide by zero");
-
-	ret = (((INT64)a * FRACUNIT)) / b;
-
-	if ((ret > INT32_MAX) || (ret < INT32_MIN))
-		I_Error("FixedDiv: divide by zero");
-	return (fixed_t)ret;
-}
-
-#endif // __USE_C_FIXEDDIV__
-
 fixed_t FixedSqrt(fixed_t x)
 {
 #ifdef HAVE_SQRT
diff --git a/src/m_fixed.h b/src/m_fixed.h
index 1cf2f00d1..83b1710f7 100644
--- a/src/m_fixed.h
+++ b/src/m_fixed.h
@@ -53,127 +53,35 @@ FUNCMATH FUNCINLINE static ATTRINLINE fixed_t FloatToFixed(float f)
 #define FIXED_TO_FLOAT(x) FixedToFloat(x) // (((float)(x)) / ((float)FRACUNIT))
 #define FLOAT_TO_FIXED(f) FloatToFixed(f) // (fixed_t)((f) * ((float)FRACUNIT))
 
+/**	\brief	The FixedMul function
 
-#if defined (__WATCOMC__) && FRACBITS == 16
-	#pragma aux FixedMul =  \
-		"imul ebx",         \
-		"shrd eax,edx,16"   \
-		parm    [eax] [ebx] \
-		value   [eax]       \
-		modify exact [eax edx]
+	\param	a	fixed_t number
+	\param	b	fixed_t number
 
-	#pragma aux FixedDiv2 = \
-		"cdq",              \
-		"shld edx,eax,16",  \
-		"sal eax,16",       \
-		"idiv ebx"          \
-		parm    [eax] [ebx] \
-		value   [eax]       \
-		modify exact [eax edx]
-#elif defined (__GNUC__) && defined (__i386__) && !defined (NOASM)
-	// i386 linux, cygwin or mingw
-	FUNCMATH FUNCINLINE static inline fixed_t FixedMul(fixed_t a, fixed_t b) // asm
-	{
-		fixed_t ret;
-		asm
-		(
-			 "imull %2;"           // a*b
-			 "shrdl %3,%%edx,%0;"  // shift logical right FRACBITS bits
-			:"=a" (ret)            // eax is always the result and the first operand (%0,%1)
-			:"0" (a), "r" (b)      // and %2 is what we use imull on with what in %1
-			, "I" (FRACBITS)       // %3 holds FRACBITS (normally 16)
-			:"cc", "%edx"         // edx and condition codes clobbered
-		);
-		return ret;
-	}
+	\return	a*b>>FRACBITS
 
-	FUNCMATH FUNCINLINE static inline fixed_t FixedDiv2(fixed_t a, fixed_t b)
-	{
-		fixed_t ret;
-		asm
-		(
-			  "movl  %1,%%edx;"    // these two instructions allow the next two to pair, on the Pentium processor.
-			  "sarl  $31,%%edx;"   // shift arithmetic right 31 on EDX
-			  "shldl %3,%1,%%edx;" // DP shift logical left FRACBITS on EDX
-			  "sall  %3,%0;"       // shift arithmetic left FRACBITS on EAX
-			  "idivl %2;"          // EDX/b = EAX
-			: "=a" (ret)
-			: "0" (a), "r" (b)
-			, "I" (FRACBITS)
-			: "%edx"
-		);
-		return ret;
-	}
-#elif defined (__GNUC__) && defined (__arm__) && !defined(__thumb__) && !defined(NOASM) //ARMv4 ASM
-	FUNCMATH FUNCINLINE static inline fixed_t FixedMul(fixed_t a, fixed_t b) // let abuse smull
-	{
-		fixed_t ret;
-		asm
-		(
-			  "smull %[lo], r1, %[a], %[b];"
-			  "mov %[lo], %[lo], lsr %3;"
-			  "orr %[lo], %[lo], r1, lsl %3;"
-			: [lo] "=&r" (ret) // rhi, rlo and rm must be distinct registers
-			: [a] "r" (a), [b] "r" (b)
-			, "i" (FRACBITS)
-			: "r1"
-		);
-		return ret;
-	}
+*/
+FUNCMATH FUNCINLINE static ATTRINLINE fixed_t FixedMul(fixed_t a, fixed_t b)
+{
+	// Need to cast to unsigned before shifting to avoid undefined behaviour
+	// for negative integers
+	return (fixed_t)(((UINT64)((INT64)a * b)) >> FRACBITS);
+}
 
-	#define __USE_C_FIXEDDIV__ // no double or asm div in ARM land
-#elif defined (__GNUC__) && defined (__ppc__) && !defined(NOASM) && 0 // WII: PPC CPU
-	FUNCMATH FUNCINLINE static inline fixed_t FixedMul(fixed_t a, fixed_t b) // asm
-	{
-		fixed_t ret, hi, lo;
-		asm
-		(
-			  "mullw %0, %2, %3;"
-			  "mulhw %1, %2, %3"
-			: "=r" (hi), "=r" (lo)
-			: "r" (a), "r" (b)
-			, "I" (FRACBITS)
-		);
-		ret = (INT64)((hi>>FRACBITS)+lo)<<FRACBITS;
-		return ret;
-	}
+/**	\brief	The FixedDiv2 function
 
-	#define __USE_C_FIXEDDIV__// Alam: I am lazy
-#elif defined (__GNUC__) && defined (__mips__) && !defined(NOASM) && 0 // PSP: MIPS CPU
-	FUNCMATH FUNCINLINE static inline fixed_t FixedMul(fixed_t a, fixed_t b) // asm
-	{
-		fixed_t ret;
-		asm
-		(
-			  "mult %3, %4;"    // a*b=h<32+l
-			: "=r" (ret), "=l" (a), "=h" (b) //todo: abuse shr opcode
-			: "0" (a), "r" (b)
-			, "I" (FRACBITS)
-			//: "+l", "+h"
-		);
-		ret = (INT64)((a>>FRACBITS)+b)<<FRACBITS;
-		return ret;
-	}
+	\param	a	fixed_t number
+	\param	b	fixed_t number
 
-	#define __USE_C_FIXEDDIV__ // no 64b asm div in MIPS land
-#elif defined (__GNUC__) && defined (__sh__) && 0 // DC: SH4 CPU
-#elif defined (__GNUC__) && defined (__m68k__) && 0 // DEAD: Motorola 6800 CPU
-#elif defined (_MSC_VER) && defined(USEASM) && FRACBITS == 16
-	// Microsoft Visual C++ (no asm inline)
-	fixed_t __cdecl FixedMul(fixed_t a, fixed_t b);
-	fixed_t __cdecl FixedDiv2(fixed_t a, fixed_t b);
-#else
-	#define __USE_C_FIXEDMUL__
-	#define __USE_C_FIXEDDIV__
-#endif
+	\return	a/b * FRACUNIT
 
-#ifdef __USE_C_FIXEDMUL__
-FUNCMATH fixed_t FixedMul(fixed_t a, fixed_t b);
-#endif
-
-#ifdef __USE_C_FIXEDDIV__
-FUNCMATH fixed_t FixedDiv2(fixed_t a, fixed_t b);
-#endif
+*/
+FUNCMATH FUNCINLINE static ATTRINLINE fixed_t FixedDiv2(fixed_t a, fixed_t b)
+{
+	// This does not check for division overflow or division by 0!
+	// That is the caller's responsibility.
+	return (fixed_t)(((INT64)a * FRACUNIT) / b);
+}
 
 /**	\brief	The FixedInt function