https://bugs.llvm.org/show_bug.cgi?id=50121
Bug ID: 50121
Summary: __attribute__((no_caller_saved_registers)) ignored for
struct members and typedefs
Product: clang
Version: trunk
Hardware: PC
OS: All
Status: NEW
Severity: normal
Priority: P
Component: -New Bugs
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected], [email protected]
Take the following program that uses no_caller_saved_registers:
__attribute__((no_caller_saved_registers)) void g();
int f(int x) {
g();
return x;
}
This produces the expected output, edi is preserved across the call:
0000000000000000 <f>:
0: 50 push rax
1: 31 c0 xor eax,eax
3: e8 00 00 00 00 call 8 <f+0x8>
4: R_X86_64_PLT32 g-0x4
8: 89 f8 mov eax,edi
a: 59 pop rcx
b: c3 ret
However the following program does not generate the same output:
struct {
__attribute__((no_caller_saved_registers)) void (*g)();
} st;
int f(int x) {
st.g();
return x;
}
In this case the attribute is ignored, and edi is spilled to a normal
callee-save register:
0000000000000000 <f>:
0: 53 push rbx
1: 89 fb mov ebx,edi
3: 31 c0 xor eax,eax
5: ff 15 00 00 00 00 call QWORD PTR [rip+0x0] # b <f+0xb>
7: R_X86_64_PC32 st-0x4
b: 89 d8 mov eax,ebx
d: 5b pop rbx
e: c3 ret
If we copy into a local variable with the attribute, it works:
struct {
__attribute__((no_caller_saved_registers)) void (*g)();
} st;
int f(int x) {
__attribute__((no_caller_saved_registers)) void (*local)() = st.g;
local();
return x;
}
However it does not work if the attribute is on a typedef:
typedef __attribute__((no_caller_saved_registers)) void g_type();
g_type *g;
int f(int x) {
g();
return x;
}
This bug appears to be similar to https://bugs.llvm.org/show_bug.cgi?id=21082
--
You are receiving this mail because:
You are on the CC list for the bug._______________________________________________
llvm-bugs mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-bugs
