llvm-project/compiler-rt/lib/ashrdi3.c

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//===-- ashrdi3.c - Implement __ashrdi3 -----------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements __ashrdi3 for the compiler_rt library.
//
//===----------------------------------------------------------------------===//
#include "int_lib.h"
// Returns: arithmetic a >> b
// Precondition: 0 <= b < bits_in_dword
di_int
__ashrdi3(di_int a, si_int b)
{
const int bits_in_word = (int)(sizeof(si_int) * CHAR_BIT);
dwords input;
dwords result;
input.all = a;
if (b & bits_in_word) // bits_in_word <= b < bits_in_dword
{
// result.high = input.high < 0 ? -1 : 0
result.high = input.high >> (bits_in_word - 1);
result.low = input.high >> (b - bits_in_word);
}
else // 0 <= b < bits_in_word
{
if (b == 0)
return a;
result.high = input.high >> b;
result.low = (input.high << (bits_in_word - b)) | (input.low >> b);
}
return result.all;
}