https://llvm.org/bugs/show_bug.cgi?id=26305
Bug ID: 26305
Summary: [X86] Failing to tail call with bool parameter
Product: libraries
Version: trunk
Hardware: PC
OS: Linux
Status: NEW
Severity: normal
Priority: P
Component: Backend: X86
Assignee: unassignedb...@nondot.org
Reporter: h...@chromium.org
CC: llvm-bugs@lists.llvm.org
Blocks: 26299
Classification: Unclassified
Consider:
void f(bool);
void g(bool x) {
f(x);
}
Clang will generate:
00000000 <_Z1gb>:
0: 83 ec 0c sub $0xc,%esp
3: 0f b6 44 24 10 movzbl 0x10(%esp),%eax
8: 89 04 24 mov %eax,(%esp)
b: e8 fc ff ff ff call c <_Z1gb+0xc>
10: 83 c4 0c add $0xc,%esp
13: c3 ret
GCC 5.3 will do the tail call, but still insists on zexting:
g(bool):
movzbl 4(%esp), %eax
movl %eax, 4(%esp)
jmp f(bool)
MSVC hits the spot and emits a single jmp:
?g@@YAX_N@Z (void __cdecl g(bool)):
00000000: E9 00 00 00 00 jmp ?f@@YAX_N@Z
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