testvacld(int n, ...) {
  __builtin_va_list ap;
  __builtin_va_start(ap, n);
  _Complex long double t = __builtin_va_arg(ap, _Complex long double);
  __builtin_va_end(ap);
}


x86 assembly (clang, -O0):
<testvacld>:
push   %rbp
mov    %rsp,%rbp
sub    $0x70,%rsp
test   %al,%al
je     113c <testvacld+0x3c>
movaps %xmm0,-0xc0(%rbp)
movaps %xmm1,-0xb0(%rbp)
movaps %xmm2,-0xa0(%rbp)
movaps %xmm3,-0x90(%rbp)
movaps %xmm4,-0x80(%rbp)
movaps %xmm5,-0x70(%rbp)
movaps %xmm6,-0x60(%rbp)
movaps %xmm7,-0x50(%rbp)
mov    %r9,-0xc8(%rbp)
mov    %r8,-0xd0(%rbp)
mov    %rcx,-0xd8(%rbp)
mov    %rdx,-0xe0(%rbp)
mov    %rsi,-0xe8(%rbp)
mov    %edi,-0x8(%rbp)
lea    -0xf0(%rbp),%rax
mov    %rax,-0x10(%rbp)
lea    0x10(%rbp),%rax
mov    %rax,-0x18(%rbp)
movl   $0x30,-0x1c(%rbp)
movl   $0x8,-0x20(%rbp)
mov    -0x18(%rbp),%rax
add    $0xf,%rax
and    $0xfffffffffffffff0,%rax
mov    %rax,%rcx
add    $0x20,%rcx
mov    %rcx,-0x18(%rbp)
fldt   (%rax)
fldt   0x10(%rax)
fxch   %st(1)
fstpt  -0x40(%rbp)
fstpt  -0x30(%rbp)
mov    -0x4(%rbp),%eax
add    $0x70,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<testvacld>:
sub    $0x48,%rsp
mov    %rsi,-0x78(%rsp)
mov    %rdx,-0x70(%rsp)
mov    %rcx,-0x68(%rsp)
mov    %r8,-0x60(%rsp)
mov    %r9,-0x58(%rsp)
test   %al,%al
je     1148 <testvacld+0x48>
movaps %xmm0,-0x50(%rsp)
movaps %xmm1,-0x40(%rsp)
movaps %xmm2,-0x30(%rsp)
movaps %xmm3,-0x20(%rsp)
movaps %xmm4,-0x10(%rsp)
movaps %xmm5,(%rsp)
movaps %xmm6,0x10(%rsp)
movaps %xmm7,0x20(%rsp)
add    $0x48,%rsp
ret

LLVM IR (-O0):
%struct.__va_list_tag = type { i32, i32, i8*, i8* }
define i32 @testvacld(i32 %0, ...) {
%2 = alloca i32
%3 = alloca i32
%4 = alloca [1 x %struct.__va_list_tag]
%5 = alloca { x86_fp80, x86_fp80 }
store i32 %0, i32* %3
%6 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %4, i64 0, i64 0
%7 = bitcast %struct.__va_list_tag* %6 to i8*
%8 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %4, i64 0, i64 0
%9 = getelementptr inbounds %struct.__va_list_tag, %struct.__va_list_tag* %8, i32 0, i32 2
%10 = load i8*, i8** %9
%11 = ptrtoint i8* %10 to i64
%12 = add i64 %11, 15
%13 = and i64 %12, -16
%14 = inttoptr i64 %13 to i8*
%15 = bitcast i8* %14 to { x86_fp80, x86_fp80 }*
%16 = getelementptr i8, i8* %14, i32 32
store i8* %16, i8** %9
%17 = getelementptr inbounds { x86_fp80, x86_fp80 }, { x86_fp80, x86_fp80 }* %15, i32 0, i32 0
%18 = load x86_fp80, x86_fp80* %17
%19 = getelementptr inbounds { x86_fp80, x86_fp80 }, { x86_fp80, x86_fp80 }* %15, i32 0, i32 1
%20 = load x86_fp80, x86_fp80* %19
%21 = getelementptr inbounds { x86_fp80, x86_fp80 }, { x86_fp80, x86_fp80 }* %5, i32 0, i32 0
%22 = getelementptr inbounds { x86_fp80, x86_fp80 }, { x86_fp80, x86_fp80 }* %5, i32 0, i32 1
store x86_fp80 %18, x86_fp80* %21
store x86_fp80 %20, x86_fp80* %22
%23 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %4, i64 0, i64 0
%24 = bitcast %struct.__va_list_tag* %23 to i8*
%25 = load i32, i32* %2
ret i32 %25
}

LLVM IR (-O2):
%struct.__va_list_tag = type { i32, i32, i8*, i8* }
define i32 @testvacld(i32 %0, ...) {
%2 = alloca [1 x %struct.__va_list_tag]
%3 = bitcast [1 x %struct.__va_list_tag]* %2 to i8*
%4 = getelementptr inbounds [1 x %struct.__va_list_tag], [1 x %struct.__va_list_tag]* %2, i64 0, i64 0, i32 2
%5 = load i8*, i8** %4
%6 = ptrtoint i8* %5 to i64
%7 = add i64 %6, 15
%8 = and i64 %7, -16
%9 = inttoptr i64 %8 to i8*
%10 = getelementptr i8, i8* %9, i64 32
store i8* %10, i8** %4
ret i32 undef
}