Adding soft-float comparisons, addition, subtraction, multiplication and negation
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@107400 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/mulsf3.c b/lib/mulsf3.c
new file mode 100644
index 0000000..8c8b314
--- /dev/null
+++ b/lib/mulsf3.c
@@ -0,0 +1,112 @@
+/*
+ * The LLVM Compiler Infrastructure
+ *
+ * This file is distributed under the University of Illinois Open Source
+ * License. See LICENSE.TXT for details.
+ */
+
+#define SINGLE_PRECISION
+#include "fp_lib.h"
+
+// This file implements single-precision soft-float multiplication with the
+// IEEE-754 default rounding (to nearest, ties to even).
+
+// 32x32 --> 64 bit multiply
+static inline void wideMultiply(rep_t a, rep_t b, rep_t *hi, rep_t *lo) {
+ const uint64_t product = (uint64_t)a*b;
+ *hi = product >> 32;
+ *lo = product;
+}
+
+fp_t __mulsf3(fp_t a, fp_t b) {
+
+ const unsigned int aExponent = toRep(a) >> significandBits & maxExponent;
+ const unsigned int bExponent = toRep(b) >> significandBits & maxExponent;
+ const rep_t productSign = (toRep(a) ^ toRep(b)) & signBit;
+
+ rep_t aSignificand = toRep(a) & significandMask;
+ rep_t bSignificand = toRep(b) & significandMask;
+ int scale = 0;
+
+ // Detect if a or b is zero, denormal, infinity, or NaN.
+ if (aExponent-1U >= maxExponent-1U || bExponent-1U >= maxExponent-1U) {
+
+ const rep_t aAbs = toRep(a) & absMask;
+ const rep_t bAbs = toRep(b) & absMask;
+
+ // NaN * anything = qNaN
+ if (aAbs > infRep) return fromRep(toRep(a) | quietBit);
+ // anything * NaN = qNaN
+ if (bAbs > infRep) return fromRep(toRep(b) | quietBit);
+
+ if (aAbs == infRep) {
+ // infinity * non-zero = +/- infinity
+ if (bAbs) return fromRep(aAbs | productSign);
+ // infinity * zero = NaN
+ else return fromRep(qnanRep);
+ }
+
+ if (bAbs == infRep) {
+ // non-zero * infinity = +/- infinity
+ if (aAbs) return fromRep(bAbs | productSign);
+ // zero * infinity = NaN
+ else return fromRep(qnanRep);
+ }
+
+ // zero * anything = +/- zero
+ if (!aAbs) return fromRep(productSign);
+ // anything * zero = +/- zero
+ if (!bAbs) return fromRep(productSign);
+
+ // one or both of a or b is denormal, the other (if applicable) is a
+ // normal number. Renormalize one or both of a and b, and set scale to
+ // include the necessary exponent adjustment.
+ if (aAbs < implicitBit) scale += normalize(&aSignificand);
+ if (bAbs < implicitBit) scale += normalize(&bSignificand);
+ }
+
+ // Or in the implicit significand bit. (If we fell through from the
+ // denormal path it was already set by normalize( ), but setting it twice
+ // won't hurt anything.)
+ aSignificand |= implicitBit;
+ bSignificand |= implicitBit;
+
+ // Get the significand of a*b. Before multiplying the significands, shift
+ // one of them left to left-align it in the field. Thus, the product will
+ // have (exponentBits + 2) integral digits, all but two of which must be
+ // zero. Normalizing this result is just a conditional left-shift by one
+ // and bumping the exponent accordingly.
+ rep_t productHi, productLo;
+ wideMultiply(aSignificand, bSignificand << exponentBits,
+ &productHi, &productLo);
+
+ int productExponent = aExponent + bExponent - exponentBias + scale;
+
+ // Normalize the significand, adjust exponent if needed.
+ if (productHi & implicitBit) productExponent++;
+ else wideLeftShift(&productHi, &productLo, 1);
+
+ // If we have overflowed the type, return +/- infinity.
+ if (productExponent >= maxExponent) return fromRep(infRep | productSign);
+
+ if (productExponent <= 0) {
+ // Result is denormal before rounding, the exponent is zero and we
+ // need to shift the significand.
+ wideRightShiftWithSticky(&productHi, &productLo, 1 - productExponent);
+ }
+
+ else {
+ // Result is normal before rounding; insert the exponent.
+ productHi &= significandMask;
+ productHi |= (rep_t)productExponent << significandBits;
+ }
+
+ // Insert the sign of the result:
+ productHi |= productSign;
+
+ // Final rounding. The final result may overflow to infinity, or underflow
+ // to zero, but those are the correct results in those cases.
+ if (productLo > signBit) productHi++;
+ if (productLo == signBit) productHi += productHi & 1;
+ return fromRep(productHi);
+}