[llvm-dev] clang emits calls to consexpr function. (original) (raw)

kamlesh kumar via llvm-dev llvm-dev at lists.llvm.org
Tue Feb 5 04:41:30 PST 2019

Hi Devs, consider below testcase

$cat test.cpp

constexpr int product() {

return 10*20;

} int main() { const int x = product(); return 0; }

$./clang test.cpp -std=c++11 -S $./clang -v clang version 9.0.0 Target: x86_64-unknown-linux-gnu

$cat test.s

main: .cfi_startproc

%bb.0:

    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset %rbp, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register %rbp
    subq    $16, %rsp
    movl    $0, -4(%rbp)
    callq   _Z7productv    //here you can see the calls to product

function xorl %ecx, %ecx movl %eax, -8(%rbp) movl %ecx, %eax addq $16, %rsp popq %rbp .cfi_def_cfa %rsp, 8 retq

while g++ do not emits calls to constexpr function $g++ test.cpp -std=c++11 $cat test.s main: .LFB1: .cfi_startproc pushq %rbp .cfi_def_cfa_offset 16 .cfi_offset 6, -16 movq %rsp, %rbp .cfi_def_cfa_register 6 movl $200, -4(%rbp) movl $0, %eax popq %rbp .cfi_def_cfa 7, 8 ret .cfi_endproc

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