xref: /openbsd-src/gnu/llvm/compiler-rt/lib/builtins/clzdi2.c (revision 1f9cb04fc6f537ca6cf5a53c28927340cba218a2)
13cab2bb3Spatrick //===-- clzdi2.c - Implement __clzdi2 -------------------------------------===//
23cab2bb3Spatrick //
33cab2bb3Spatrick // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
43cab2bb3Spatrick // See https://llvm.org/LICENSE.txt for license information.
53cab2bb3Spatrick // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
63cab2bb3Spatrick //
73cab2bb3Spatrick //===----------------------------------------------------------------------===//
83cab2bb3Spatrick //
93cab2bb3Spatrick // This file implements __clzdi2 for the compiler_rt library.
103cab2bb3Spatrick //
113cab2bb3Spatrick //===----------------------------------------------------------------------===//
123cab2bb3Spatrick 
133cab2bb3Spatrick #include "int_lib.h"
143cab2bb3Spatrick 
153cab2bb3Spatrick // Returns: the number of leading 0-bits
163cab2bb3Spatrick 
173cab2bb3Spatrick #if !defined(__clang__) &&                                                     \
183cab2bb3Spatrick     ((defined(__sparc__) && defined(__arch64__)) || defined(__mips64) ||       \
193cab2bb3Spatrick      (defined(__riscv) && __SIZEOF_POINTER__ >= 8))
203cab2bb3Spatrick // On 64-bit architectures with neither a native clz instruction nor a native
213cab2bb3Spatrick // ctz instruction, gcc resolves __builtin_clz to __clzdi2 rather than
223cab2bb3Spatrick // __clzsi2, leading to infinite recursion.
233cab2bb3Spatrick #define __builtin_clz(a) __clzsi2(a)
24*1f9cb04fSpatrick extern int __clzsi2(si_int);
253cab2bb3Spatrick #endif
263cab2bb3Spatrick 
273cab2bb3Spatrick // Precondition: a != 0
283cab2bb3Spatrick 
__clzdi2(di_int a)29*1f9cb04fSpatrick COMPILER_RT_ABI int __clzdi2(di_int a) {
303cab2bb3Spatrick   dwords x;
313cab2bb3Spatrick   x.all = a;
323cab2bb3Spatrick   const si_int f = -(x.s.high == 0);
33*1f9cb04fSpatrick   return clzsi((x.s.high & ~f) | (x.s.low & f)) +
343cab2bb3Spatrick          (f & ((si_int)(sizeof(si_int) * CHAR_BIT)));
353cab2bb3Spatrick }
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