clzdi2.c revision 1c5f89b1dd741135a4007ab577723d422f421eec
12bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan/* ===-- clzdi2.c - Implement __clzdi2 -------------------------------------=== 22bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * 31c5f89b1dd741135a4007ab577723d422f421eecAnton Korobeynikov * The LLVM Compiler Infrastructure 42bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * 59ad441ffec97db647fee3725b3424284fb913e14Howard Hinnant * This file is dual licensed under the MIT and the University of Illinois Open 69ad441ffec97db647fee3725b3424284fb913e14Howard Hinnant * Source Licenses. See LICENSE.TXT for details. 72bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * 82bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * ===----------------------------------------------------------------------=== 92bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * 102bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * This file implements __clzdi2 for the compiler_rt library. 112bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * 122bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan * ===----------------------------------------------------------------------=== 132bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan */ 141c5f89b1dd741135a4007ab577723d422f421eecAnton Korobeynikov#include "abi.h" 15b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 16b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar#include "int_lib.h" 17b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 182bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan/* Returns: the number of leading 0-bits */ 19b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 202bf62728b8ce00e295c7bf0fb328427496cc85aaEdward O'Callaghan/* Precondition: a != 0 */ 21b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar 221c5f89b1dd741135a4007ab577723d422f421eecAnton KorobeynikovCOMPILER_RT_ABI si_int 23b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar__clzdi2(di_int a) 24b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar{ 25b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar dwords x; 26b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar x.all = a; 278bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan const si_int f = -(x.s.high == 0); 288bf1e094893cb24796137b47ee0d46d18d299996Edward O'Callaghan return __builtin_clz((x.s.high & ~f) | (x.s.low & f)) + 29b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar (f & ((si_int)(sizeof(si_int) * CHAR_BIT))); 30b3a6901e66f55b35aa9e01bcb24134e6a65ea004Daniel Dunbar} 31