1  /* go-memclr.c -- clear a memory buffer
       2  
       3     Copyright 2016 The Go Authors. All rights reserved.
       4     Use of this source code is governed by a BSD-style
       5     license that can be found in the LICENSE file.  */
       6  
       7  #include "runtime.h"
       8  
       9  void memclrNoHeapPointers(void *, uintptr)
      10    __asm__ (GOSYM_PREFIX "runtime.memclrNoHeapPointers")
      11    __attribute__ ((no_split_stack));
      12  
      13  void
      14  memclrNoHeapPointers (void *p1, uintptr len)
      15  {
      16  
      17  #if !defined(__PPC64__)
      18    __builtin_memset(p1, 0, len);
      19  #else
      20    int64 rem,drem,i;
      21    uint64 offset;
      22    volatile uint64 *vp;
      23  
      24    if (len == 0) {
      25      return;
      26    }
      27    rem = len;
      28  
      29    offset = (uint64)p1 % 8;
      30    // This memset is OK since it can't contain
      31    // an 8 byte aligned pointer.
      32    if ((rem < 8) || (offset > 0 && offset+rem <= 16)) {
      33      __builtin_memset(p1, 0, rem);
      34      return;
      35    }
      36    // Move initial bytes to get to 8 byte boundary
      37    if (offset > 0) {
      38      __builtin_memset(p1, 0, 8-offset);
      39      p1 = (void*)((char*)p1+8-offset);
      40      rem -= 8-offset;
      41    }
      42  
      43    // If at least 8 bytes left, clear
      44    drem = rem>>3;
      45  
      46    vp = (volatile uint64*)(p1);
      47    // Without the use of volatile here, the compiler
      48    // might convert the loop into a memset.
      49    for (i=0; i<drem; i++) {
      50      *vp = 0;
      51      vp++;
      52      rem -= 8;
      53    }
      54    p1 = (void*)((char*)p1 + 8*drem);
      55    // Clear any remaining
      56    if (rem > 0) {
      57      __builtin_memset (p1, 0, rem);
      58    }
      59  #endif
      60  }