http://llvm.org/bugs/show_bug.cgi?id=3975
Summary: llvm-gcc has some problem with int128 arithmetic
Product: tools
Version: 2.2
Platform: PC
OS/Version: All
Status: NEW
Keywords: miscompilation
Severity: normal
Priority: P2
Component: llvm-g++
AssignedTo: [email protected]
ReportedBy: [email protected]
CC: [email protected], [email protected]
Consider this at -m64:
__uint128_t test2() {
const __uint128_t c_zero = ~0;
return c_zero;
}
This should compile to all 128 ones because the -1 signed integer sign extends
to i128. GCC produces the correct code:
__Z5test2v:
LFB8:
pushq %rbp
LCFI0:
movq %rsp, %rbp
LCFI1:
movq $-1, %rax
movq $-1, %rdx
leave
ret
but we compile it to 64 ones:
define i128 @_Z5test2v() nounwind readnone {
entry:
ret i128 18446744073709551615
}
I think this is some problem in llvm-gcc, because the -O0 IR is already wrong:
store i128 18446744073709551615, i128* %c_zero, align 16
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