1 files changed, 104 insertions, 0 deletions
diff --git a/lib/ppc/fixtfdi.c b/lib/ppc/fixtfdi.c
new file mode 100644
index 000000000000..fa113a037e93
--- /dev/null
+++ b/lib/ppc/fixtfdi.c
@@ -0,0 +1,104 @@
+/* This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ */
+
+/* int64_t __fixunstfdi(long double x);
+ * This file implements the PowerPC 128-bit double-double -> int64_t conversion
+ */
+
+#include "DD.h"
+#include <stdint.h>
+
+uint64_t __fixtfdi(long double input)
+{
+	const DD x = { .ld = input };
+	const doublebits hibits = { .d = x.s.hi };
+	
+	const uint32_t absHighWord = (uint32_t)(hibits.x >> 32) & UINT32_C(0x7fffffff);
+	const uint32_t absHighWordMinusOne = absHighWord - UINT32_C(0x3ff00000);
+	
+	/* If (1.0 - tiny) <= input < 0x1.0p63: */
+	if (UINT32_C(0x03f00000) > absHighWordMinusOne)
+	{
+		/* Do an unsigned conversion of the absolute value, then restore the sign. */
+		const int unbiasedHeadExponent = absHighWordMinusOne >> 20;
+		
+		int64_t result = hibits.x & INT64_C(0x000fffffffffffff); /* mantissa(hi) */
+		result |= INT64_C(0x0010000000000000); /* matissa(hi) with implicit bit */
+		result <<= 10; /* mantissa(hi) with one zero preceeding bit. */
+		
+		const int64_t hiNegationMask = ((int64_t)(hibits.x)) >> 63;
+		
+		/* If the tail is non-zero, we need to patch in the tail bits. */
+		if (0.0 != x.s.lo)
+		{
+			const doublebits lobits = { .d = x.s.lo };
+			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
+			tailMantissa |= INT64_C(0x0010000000000000);
+			
+			/* At this point we have the mantissa of |tail| */
+			/* We need to negate it if head and tail have different signs. */
+			const int64_t loNegationMask = ((int64_t)(lobits.x)) >> 63;
+			const int64_t negationMask = loNegationMask ^ hiNegationMask;
+			tailMantissa = (tailMantissa ^ negationMask) - negationMask;
+			
+			/* Now we have the mantissa of tail as a signed 2s-complement integer */
+			
+			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
+			
+			/* Shift the tail mantissa into the right position, accounting for the
+			 * bias of 10 that we shifted the head mantissa by.
+			 */ 
+			tailMantissa >>= (unbiasedHeadExponent - (biasedTailExponent - (1023 - 10)));
+			
+			result += tailMantissa;
+		}
+		
+		result >>= (62 - unbiasedHeadExponent);
+		
+		/* Restore the sign of the result and return */
+		result = (result ^ hiNegationMask) - hiNegationMask;
+		return result;
+		
+	}
+
+	/* Edge cases handled here: */
+	
+	/* |x| < 1, result is zero. */
+	if (1.0 > __builtin_fabs(x.s.hi))
+		return INT64_C(0);
+	
+	/* x very close to INT64_MIN, care must be taken to see which side we are on. */
+	if (x.s.hi == -0x1.0p63) {
+		
+		int64_t result = INT64_MIN;
+		
+		if (0.0 < x.s.lo)
+		{
+			/* If the tail is positive, the correct result is something other than INT64_MIN.
+			 * we'll need to figure out what it is.
+			 */
+
+			const doublebits lobits = { .d = x.s.lo };
+			int64_t tailMantissa = lobits.x & INT64_C(0x000fffffffffffff);
+			tailMantissa |= INT64_C(0x0010000000000000);
+			
+			/* Now we negate the tailMantissa */
+			tailMantissa = (tailMantissa ^ INT64_C(-1)) + INT64_C(1);
+			
+			/* And shift it by the appropriate amount */
+			const int biasedTailExponent = (int)(lobits.x >> 52) & 0x7ff;
+			tailMantissa >>= 1075 - biasedTailExponent;
+			
+			result -= tailMantissa;
+		}
+		
+		return result;
+	}
+	
+	/* Signed overflows, infinities, and NaNs */
+	if (x.s.hi > 0.0)
+		return INT64_MAX;
+	else
+		return INT64_MIN;
+}