unsigned int rbuDeltaGetInt(const char **pz, int *pLen) {
  static const signed char zValue[] = {
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
      0,  1,  2,  3,  4,  5,  6,  7,  8,  9,  -1, -1, -1, -1, -1, -1,
      -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
      25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, -1, 36,
      -1, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
      52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, -1, -1, -1, 63, -1,
  };
  unsigned int v = 0;
  int c;
  unsigned char *z = (unsigned char *)*pz;
  unsigned char *zStart = z;
  while ((c = zValue[0x7f & *(z++)]) >= 0) {
    v = (v << 6) + c;
  }
  z--;
  *pLen -= z - zStart;
  *pz = (char *)z;
  return v;
}


x86 assembly (clang, -O0):
<rbuDeltaGetInt>:
push   %rbp
mov    %rsp,%rbp
mov    %rdi,-0x8(%rbp)
mov    %rsi,-0x10(%rbp)
movl   $0x0,-0x14(%rbp)
mov    -0x8(%rbp),%rax
mov    (%rax),%rax
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rax
mov    %rax,-0x28(%rbp)
mov    -0x20(%rbp),%rax
mov    %rax,%rcx
add    $0x1,%rcx
mov    %rcx,-0x20(%rbp)
movzbl (%rax),%eax
and    $0x7f,%eax
movslq %eax,%rcx
lea    0xebb(%rip),%rax
movsbl (%rax,%rcx,1),%eax
mov    %eax,-0x18(%rbp)
cmp    $0x0,%eax
jl     1166 <rbuDeltaGetInt+0x66>
mov    -0x14(%rbp),%eax
shl    $0x6,%eax
add    -0x18(%rbp),%eax
mov    %eax,-0x14(%rbp)
jmp    1126 <rbuDeltaGetInt+0x26>
mov    -0x20(%rbp),%rax
add    $0xffffffffffffffff,%rax
mov    %rax,-0x20(%rbp)
mov    -0x20(%rbp),%rdx
mov    -0x28(%rbp),%rax
sub    %rax,%rdx
mov    -0x10(%rbp),%rax
movslq (%rax),%rcx
sub    %rdx,%rcx
mov    %ecx,(%rax)
mov    -0x20(%rbp),%rcx
mov    -0x8(%rbp),%rax
mov    %rcx,(%rax)
mov    -0x14(%rbp),%eax
pop    %rbp
ret

x86 assembly (clang, -O2):
<rbuDeltaGetInt>:
mov    (%rdi),%r8
movzbl (%r8),%eax
and    $0x7f,%eax
lea    0xeef(%rip),%r9
mov    (%rax,%r9,1),%cl
xor    %eax,%eax
mov    %r8,%rdx
test   %cl,%cl
js     113c <rbuDeltaGetInt+0x3c>
xchg   %ax,%ax
movzbl %cl,%ecx
shl    $0x6,%eax
add    %ecx,%eax
movzbl 0x1(%rdx),%ecx
add    $0x1,%rdx
and    $0x7f,%ecx
movzbl (%rcx,%r9,1),%ecx
test   %cl,%cl
jns    1120 <rbuDeltaGetInt+0x20>
sub    %edx,%r8d
add    %r8d,(%rsi)
mov    %rdx,(%rdi)
ret

LLVM IR (-O0):
@rbuDeltaGetInt.zValue = internal constant [128 x i8] c"\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\00\01\02\03\04\05\06\07\08\09\FF\FF\FF\FF\FF\FF\FF\0A\0B\0C\0D\0E\0F\10\11\12\13\14\15\16\17\18\19\1A\1B\1C\1D\1E\1F !\22#\FF\FF\FF\FF$\FF%&'()*+,-./0123456789:;<=>\FF\FF\FF?\FF"
define i32 @rbuDeltaGetInt(i8** %0, i32* %1) {
%3 = alloca i8**
%4 = alloca i32*
%5 = alloca i32
%6 = alloca i32
%7 = alloca i8*
%8 = alloca i8*
store i8** %0, i8*** %3
store i32* %1, i32** %4
store i32 0, i32* %5
%9 = load i8**, i8*** %3
%10 = load i8*, i8** %9
store i8* %10, i8** %7
%11 = load i8*, i8** %7
store i8* %11, i8** %8
br label %12
12: ; preds = %23, %2
%13 = load i8*, i8** %7
%14 = getelementptr inbounds i8, i8* %13, i32 1
store i8* %14, i8** %7
%15 = load i8, i8* %13
%16 = zext i8 %15 to i32
%17 = and i32 127, %16
%18 = sext i32 %17 to i64
%19 = getelementptr inbounds [128 x i8], [128 x i8]* @rbuDeltaGetInt.zValue, i64 0, i64 %18
%20 = load i8, i8* %19
%21 = sext i8 %20 to i32
store i32 %21, i32* %6
%22 = icmp sge i32 %21, 0
br i1 %22, label %23, label %28
23: ; preds = %12
%24 = load i32, i32* %5
%25 = shl i32 %24, 6
%26 = load i32, i32* %6
%27 = add i32 %25, %26
store i32 %27, i32* %5
br label %12
28: ; preds = %12
%29 = load i8*, i8** %7
%30 = getelementptr inbounds i8, i8* %29, i32 -1
store i8* %30, i8** %7
%31 = load i8*, i8** %7
%32 = load i8*, i8** %8
%33 = ptrtoint i8* %31 to i64
%34 = ptrtoint i8* %32 to i64
%35 = sub i64 %33, %34
%36 = load i32*, i32** %4
%37 = load i32, i32* %36
%38 = sext i32 %37 to i64
%39 = sub nsw i64 %38, %35
%40 = trunc i64 %39 to i32
store i32 %40, i32* %36
%41 = load i8*, i8** %7
%42 = load i8**, i8*** %3
store i8* %41, i8** %42
%43 = load i32, i32* %5
ret i32 %43
}

LLVM IR (-O2):
@rbuDeltaGetInt.zValue = internal unnamed_addr constant [128 x i8] c"\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\FF\00\01\02\03\04\05\06\07\08\09\FF\FF\FF\FF\FF\FF\FF\0A\0B\0C\0D\0E\0F\10\11\12\13\14\15\16\17\18\19\1A\1B\1C\1D\1E\1F !\22#\FF\FF\FF\FF$\FF%&'()*+,-./0123456789:;<=>\FF\FF\FF?\FF"
define i32 @rbuDeltaGetInt(i8** nocapture %0, i32* nocapture %1) {
%3 = load i8*, i8** %0
%4 = load i8, i8* %3
%5 = and i8 %4, 127
%6 = zext i8 %5 to i64
%7 = getelementptr inbounds [128 x i8], [128 x i8]* @rbuDeltaGetInt.zValue, i64 0, i64 %6
%8 = load i8, i8* %7
%9 = icmp sgt i8 %8, -1
br i1 %9, label %10, label %24
10: ; preds = %2, %10
%11 = phi i8 [ %22, %10 ], [ %8, %2 ]
%12 = phi i32 [ %17, %10 ], [ 0, %2 ]
%13 = phi i8* [ %14, %10 ], [ %3, %2 ]
%14 = getelementptr inbounds i8, i8* %13, i64 1
%15 = zext i8 %11 to i32
%16 = shl i32 %12, 6
%17 = add i32 %16, %15
%18 = load i8, i8* %14
%19 = and i8 %18, 127
%20 = zext i8 %19 to i64
%21 = getelementptr inbounds [128 x i8], [128 x i8]* @rbuDeltaGetInt.zValue, i64 0, i64 %20
%22 = load i8, i8* %21
%23 = icmp sgt i8 %22, -1
br i1 %23, label %10, label %24
24: ; preds = %10, %2
%25 = phi i8* [ %3, %2 ], [ %14, %10 ]
%26 = phi i32 [ 0, %2 ], [ %17, %10 ]
%27 = ptrtoint i8* %25 to i64
%28 = ptrtoint i8* %3 to i64
%29 = sub i64 %28, %27
%30 = load i32, i32* %1
%31 = trunc i64 %29 to i32
%32 = add i32 %30, %31
store i32 %32, i32* %1
store i8* %25, i8** %0
ret i32 %26
}