https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88739
Bug ID: 88739
Summary: union bug on ARM64
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dongjianqiang2 at huawei dot com
Target Milestone: ---
Created attachment 45364
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45364&action=edit
demo code to recur error
#include<stdio.h>
typedef unsigned int U32;
typedef unsigned short U16;
typedef unsigned char U8;
typedef struct MEM_HEAD_4DW
{
/* first word */
U32 b11 : 1;
U32 b12 : 3;
U32 b13 : 3;
U32 b14 : 1;
U32 b15 : 16;
U32 b16 : 8;
/* second word */
U32 b21 : 16;
U32 b22 : 1;
U32 b23 : 4;
U32 b24 : 11;
/* third word */
U32 b31 : 32;
/* fourth word */
U32 b30AddrL : 30;
U32 b2AddrType : 2;
}MEM_REQ_HEAD_4DW;
typedef union HEAD_DW4_UNION
{
MEM_REQ_HEAD_4DW strMemHead;
U32 aulValue[4];
U16 ausValue[8];
U8 aucValue[16];
}HEAD_REQ_DW4_UNION;
U32 Test_func(U32 ulAddr)
{
HEAD_REQ_DW4_UNION unData;
unData.strMemHead.b30AddrL = ulAddr >> 2;
unData.strMemHead.b2AddrType = 0;
printf("unData.strMemHead.b30AddrL=0x%x\r\n",unData.strMemHead.b30AddrL);
printf("unData.strMemHead.b2AddrType=0x%x\r\n",unData.strMemHead.b2AddrType);
printf("unData.aulValue[3]=0x%x\r\n",unData.aulValue[3]); // 0000
0000 0000 0001 0000 0010 0010 0100
printf("unData.ausValue[6]=0x%x\r\n",unData.ausValue[6]); // why get
0x0 instead of 0x1 ?
printf("unData.ausValue[7]=0x%x\r\n",unData.ausValue[7]);
return 0;
}
int main()
{
Test_func(0x10224);
return 0;
}
Hi,
For ARM64 big-endian, when compiled above code with -O0, the output of
ausValue[6] is 0x1 which is correct, but when I try to compile with -O1 or -O2,
the output of ausValue[6] is 0x0 which is wrong. Will appreciate if you can
help me look into this issue? is this gcc bug?
