DecUnitVector(v, c) double v[3];
unsigned char *c;
{
  v[0] = DecUnitFloat(c[0]);
  v[1] = DecUnitFloat(c[1]);
  v[2] = DecUnitFloat(c[2]);
}


x86 assembly (clang, -O0):
<DecUnitVector>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %rdi,-0x10(%rbp)
mov    %rsi,-0x18(%rbp)
mov    -0x18(%rbp),%rax
movzbl (%rax),%edi
mov    $0x0,%al
call   1030 <DecUnitFloat@plt>
cvtsi2sd %eax,%xmm0
mov    -0x10(%rbp),%rax
movsd  %xmm0,(%rax)
mov    -0x18(%rbp),%rax
movzbl 0x1(%rax),%edi
mov    $0x0,%al
call   1030 <DecUnitFloat@plt>
cvtsi2sd %eax,%xmm0
mov    -0x10(%rbp),%rax
movsd  %xmm0,0x8(%rax)
mov    -0x18(%rbp),%rax
movzbl 0x2(%rax),%edi
mov    $0x0,%al
call   1030 <DecUnitFloat@plt>
cvtsi2sd %eax,%xmm0
mov    -0x10(%rbp),%rax
movsd  %xmm0,0x10(%rax)
mov    -0x4(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<DecUnitVector>:
push   %r14
push   %rbx
push   %rax
mov    %rsi,%rbx
mov    %rdi,%r14
movzbl (%rsi),%edi
xor    %eax,%eax
call   1030 <DecUnitFloat@plt>
cvtsi2sd %eax,%xmm0
movsd  %xmm0,(%r14)
movzbl 0x1(%rbx),%edi
xor    %eax,%eax
call   1030 <DecUnitFloat@plt>
xorps  %xmm0,%xmm0
cvtsi2sd %eax,%xmm0
movsd  %xmm0,0x8(%r14)
movzbl 0x2(%rbx),%edi
xor    %eax,%eax
call   1030 <DecUnitFloat@plt>
xorps  %xmm0,%xmm0
cvtsi2sd %eax,%xmm0
movsd  %xmm0,0x10(%r14)
add    $0x8,%rsp
pop    %rbx
pop    %r14
ret

LLVM IR (-O0):
define i32 @DecUnitVector(double* %0, i8* %1) {
%3 = alloca i32
%4 = alloca double*
%5 = alloca i8*
store double* %0, double** %4
store i8* %1, i8** %5
%6 = load i8*, i8** %5
%7 = getelementptr inbounds i8, i8* %6, i64 0
%8 = load i8, i8* %7
%9 = zext i8 %8 to i32
%10 = call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %9)
%11 = sitofp i32 %10 to double
%12 = load double*, double** %4
%13 = getelementptr inbounds double, double* %12, i64 0
store double %11, double* %13
%14 = load i8*, i8** %5
%15 = getelementptr inbounds i8, i8* %14, i64 1
%16 = load i8, i8* %15
%17 = zext i8 %16 to i32
%18 = call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %17)
%19 = sitofp i32 %18 to double
%20 = load double*, double** %4
%21 = getelementptr inbounds double, double* %20, i64 1
store double %19, double* %21
%22 = load i8*, i8** %5
%23 = getelementptr inbounds i8, i8* %22, i64 2
%24 = load i8, i8* %23
%25 = zext i8 %24 to i32
%26 = call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %25)
%27 = sitofp i32 %26 to double
%28 = load double*, double** %4
%29 = getelementptr inbounds double, double* %28, i64 2
store double %27, double* %29
%30 = load i32, i32* %3
ret i32 %30
}

LLVM IR (-O2):
define i32 @DecUnitVector(double* nocapture writeonly %0, i8* nocapture %1) {
%3 = load i8, i8* %1
%4 = zext i8 %3 to i32
%5 = tail call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %4)
%6 = sitofp i32 %5 to double
store double %6, double* %0
%7 = getelementptr inbounds i8, i8* %1, i64 1
%8 = load i8, i8* %7
%9 = zext i8 %8 to i32
%10 = tail call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %9)
%11 = sitofp i32 %10 to double
%12 = getelementptr inbounds double, double* %0, i64 1
store double %11, double* %12
%13 = getelementptr inbounds i8, i8* %1, i64 2
%14 = load i8, i8* %13
%15 = zext i8 %14 to i32
%16 = tail call i32 (i32, ...) bitcast (i32 (...)* @DecUnitFloat to i32 (i32, ...)*)(i32 %15)
%17 = sitofp i32 %16 to double
%18 = getelementptr inbounds double, double* %0, i64 2
store double %17, double* %18
ret i32 undef
}