diff options
Diffstat (limited to 'compiler-rt/lib/builtins/ppc/fixunstfdi.c')
-rw-r--r-- | compiler-rt/lib/builtins/ppc/fixunstfdi.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/compiler-rt/lib/builtins/ppc/fixunstfdi.c b/compiler-rt/lib/builtins/ppc/fixunstfdi.c new file mode 100644 index 000000000000..8d53f372527a --- /dev/null +++ b/compiler-rt/lib/builtins/ppc/fixunstfdi.c @@ -0,0 +1,57 @@ +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception + +// uint64_t __fixunstfdi(long double x); +// This file implements the PowerPC 128-bit double-double -> uint64_t conversion + +#include "DD.h" + +uint64_t __fixunstfdi(long double input) { + const DD x = {.ld = input}; + const doublebits hibits = {.d = x.s.hi}; + + const uint32_t highWordMinusOne = + (uint32_t)(hibits.x >> 32) - UINT32_C(0x3ff00000); + + // If (1.0 - tiny) <= input < 0x1.0p64: + if (UINT32_C(0x04000000) > highWordMinusOne) { + const int unbiasedHeadExponent = highWordMinusOne >> 20; + + uint64_t result = hibits.x & UINT64_C(0x000fffffffffffff); // mantissa(hi) + result |= UINT64_C(0x0010000000000000); // matissa(hi) with implicit bit + result <<= 11; // mantissa(hi) left aligned in the int64 field. + + // 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| + + const int64_t negationMask = ((int64_t)(lobits.x)) >> 63; + 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 11 that we shifted the head mantissa by. + tailMantissa >>= + (unbiasedHeadExponent - (biasedTailExponent - (1023 - 11))); + + result += tailMantissa; + } + + result >>= (63 - unbiasedHeadExponent); + return result; + } + + // Edge cases are handled here, with saturation. + if (1.0 > x.s.hi) + return UINT64_C(0); + else + return UINT64_MAX; +} |