https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98364
Bug ID: 98364
Summary: C++20 module binary bloat
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: unlvsur at live dot com
Target Milestone: ---
the module will generate _ZGIW5helloEv which is dead code. There is no way to
remove them.
naive binary without module:
#include<cstdio>
int main()
{
puts("Hello World\n");
}
Disassembly of section .text:
0000000000401040 <main>:
401040: 48 83 ec 08 sub $0x8,%rsp
401044: bf 04 20 40 00 mov $0x402004,%edi
401049: e8 e2 ff ff ff callq 401030 <puts@plt>
40104e: 31 c0 xor %eax,%eax
401050: 48 83 c4 08 add $0x8,%rsp
401054: c3 retq
401055: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
40105c: 00 00 00
40105f: 90 nop
0000000000401060 <set_fast_math>:
401060: f3 0f 1e fa endbr64
401064: 0f ae 5c 24 fc stmxcsr -0x4(%rsp)
401069: 81 4c 24 fc 40 80 00 orl $0x8040,-0x4(%rsp)
401070: 00
401071: 0f ae 54 24 fc ldmxcsr -0x4(%rsp)
401076: c3 retq
401077: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
40107e: 00 00
module binary:
0000000000401050 <main>:
401050: 48 83 ec 08 sub $0x8,%rsp
401054: bf 04 20 40 00 mov $0x402004,%edi
401059: e8 d2 ff ff ff callq 401030 <puts@plt>
40105e: 31 c0 xor %eax,%eax
401060: 48 83 c4 08 add $0x8,%rsp
401064: c3 retq
401065: 66 66 2e 0f 1f 84 00 data16 nopw %cs:0x0(%rax,%rax,1)
40106c: 00 00 00 00
0000000000401070 <_GLOBAL__sub_I_main>:
401070: e9 0b 00 00 00 jmpq 401080 <_ZGIW5helloEv>
401075: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
40107c: 00 00 00
40107f: 90 nop
0000000000401080 <_ZGIW5helloEv>:
401080: 80 3d b2 2f 00 00 00 cmpb $0x0,0x2fb2(%rip) #
404039 <_ZZ13_ZGIW5helloEvE9__in_chrg>
401087: 75 07 jne 401090 <_ZGIW5helloEv+0x10>
401089: c6 05 a9 2f 00 00 01 movb $0x1,0x2fa9(%rip) #
404039 <_ZZ13_ZGIW5helloEvE9__in_chrg>
401090: c3 retq
401091: 66 2e 0f 1f 84 00 00 nopw %cs:0x0(%rax,%rax,1)
401098: 00 00 00
40109b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
00000000004010a0 <set_fast_math>:
4010a0: f3 0f 1e fa endbr64
4010a4: 0f ae 5c 24 fc stmxcsr -0x4(%rsp)
4010a9: 81 4c 24 fc 40 80 00 orl $0x8040,-0x4(%rsp)
4010b0: 00
4010b1: 0f ae 54 24 fc ldmxcsr -0x4(%rsp)
4010b6: c3 retq
4010b7: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
4010be: 00 00
