| Summary: | g++ optimizer(-O2) generates wrong code in 32bit mode on x86_64 | ||
|---|---|---|---|
| Product: | gcc | Reporter: | Michael Yan <myan> |
| Component: | c++ | Assignee: | Not yet assigned to anyone <unassigned> |
| Status: | RESOLVED DUPLICATE | ||
| Severity: | normal | CC: | attardi, cdfrey, chiabaut, Dries.Decock, gcc-bugs, gcc2eran, hans.buchmann.wantuch, honza, lucifer_ww, mihai.dontu, myan, rosenfeld, sb, schendel, sorenj, stillzhang, takahisa.yokota, tompa-l |
| Priority: | P3 | ||
| Version: | 3.4.6 | ||
| Target Milestone: | --- | ||
| Host: | Target: | ||
| Build: | Known to work: | ||
| Known to fail: | Last reconfirmed: | ||
| Attachments: | A small test file shows the problem. | ||
Created attachment 14487 [details]
A small test file shows the problem.
The attached source file has all the information of this bug report.
|
#include <stdio.h> #include <stdlib.h> #include <string.h> // g++ optimizer(-O2) generates wrong code on 32bit x86_64 // // g++ 3.2.3 is ok // g++ 3.4.6 & 4.1.1 are wrong // // platform Redhat AS4, x86_64 // // g++ -g -O2 -m32 foo.cpp typedef struct _GUID { unsigned int Data1; unsigned short Data2; unsigned short Data3; unsigned char Data4[ 8 ]; } GUID; inline bool IsGUIDNULL(const ::GUID& irGUID) { return ( (reinterpret_cast<const int*>(&irGUID))[0] == 0 && (reinterpret_cast<const int*>(&irGUID))[1] == 0 && (reinterpret_cast<const int*>(&irGUID))[2] == 0 && (reinterpret_cast<const int*>(&irGUID))[3] == 0); } /* objdump result of the following bar() function 08048450 <_Z3barv>: 8048450: 55 push %ebp 8048451: 31 c0 xor %eax,%eax 8048453: 89 e5 mov %esp,%ebp 8048455: 83 ec 28 sub $0x28,%esp 8048458: 8b 55 ec mov 0xffffffec(%ebp),%edx 804845b: c7 45 e8 00 00 00 00 movl $0x0,0xffffffe8(%ebp) 8048462: 66 c7 45 ec 00 00 movw $0x0,0xffffffec(%ebp) 8048468: 66 c7 45 ee 00 00 movw $0x0,0xffffffee(%ebp) 804846e: c6 45 f0 00 movb $0x0,0xfffffff0(%ebp) 8048472: c6 45 f1 00 movb $0x0,0xfffffff1(%ebp) 8048476: 85 d2 test %edx,%edx 8048478: c6 45 f2 00 movb $0x0,0xfffffff2(%ebp) 804847c: c6 45 f3 00 movb $0x0,0xfffffff3(%ebp) 8048480: c6 45 f4 00 movb $0x0,0xfffffff4(%ebp) 8048484: c6 45 f5 00 movb $0x0,0xfffffff5(%ebp) 8048488: c6 45 f6 00 movb $0x0,0xfffffff6(%ebp) 804848c: c6 45 f7 00 movb $0x0,0xfffffff7(%ebp) 8048490: 75 10 jne 80484a2 <_Z3barv+0x52> 8048492: 8b 4d f0 mov 0xfffffff0(%ebp),%ecx 8048495: 85 c9 test %ecx,%ecx 8048497: 75 09 jne 80484a2 <_Z3barv+0x52> 8048499: 8b 55 f4 mov 0xfffffff4(%ebp),%edx 804849c: 85 d2 test %edx,%edx 804849e: 75 02 jne 80484a2 <_Z3barv+0x52> 80484a0: b0 01 mov $0x1,%al 80484a2: 85 c0 test %eax,%eax 80484a4: 74 02 je 80484a8 <_Z3barv+0x58> 80484a6: c9 leave 80484a7: c3 ret 80484a8: c7 44 24 04 bc 85 04 movl $0x80485bc,0x4(%esp) 80484af: 08 80484b0: a1 5c 97 04 08 mov 0x804975c,%eax 80484b5: 89 04 24 mov %eax,(%esp) 80484b8: e8 af fe ff ff call 804836c <fprintf@plt> 80484bd: c9 leave 80484be: c3 ret 80484bf: 90 nop */ void bar() { GUID guid; guid.Data1 = 0; guid.Data2 = 0; guid.Data3 = 0; guid.Data4[0] = 0; guid.Data4[1] = 0; guid.Data4[2] = 0; guid.Data4[3] = 0; guid.Data4[4] = 0; guid.Data4[5] = 0; guid.Data4[6] = 0; guid.Data4[7] = 0; if (!IsGUIDNULL(guid)) { // Fails here fprintf(stderr, "test failed\n"); } } int main(int argc, char*argv[]) { int i=0; bar(); return i; }