#define NULL ((void *)0)
typedef unsigned long size_t; // Customize by platform.
typedef long intptr_t;
typedef unsigned long uintptr_t;
typedef long scalar_t__; // Either arithmetic or pointer type.
/* By default, we understand bool (as a convenience). */
typedef int bool;
#define false 0
#define true 1

/* Forward declarations */

/* Type definitions */

/* Variables and functions */
int read(int, char *, int);
int read_size(int fd, char *buf, int size) {
  int got = 0, rc;
  while ((got < size) && ((rc = read(fd, buf + got, size - got)) > 0)) {
    got += rc;
  }
  return got;
}


x86 assembly (clang, -O0):
<read_size>:
push   %rbp
mov    %rsp,%rbp
sub    $0x20,%rsp
mov    %edi,-0x4(%rbp)
mov    %rsi,-0x10(%rbp)
mov    %edx,-0x14(%rbp)
movl   $0x0,-0x18(%rbp)
mov    -0x18(%rbp),%ecx
xor    %eax,%eax
cmp    -0x14(%rbp),%ecx
mov    %al,-0x1d(%rbp)
jge    115f <read_size+0x4f>
mov    -0x4(%rbp),%edi
mov    -0x10(%rbp),%rsi
movslq -0x18(%rbp),%rax
add    %rax,%rsi
mov    -0x14(%rbp),%edx
sub    -0x18(%rbp),%edx
call   1030 <read@plt>
mov    %eax,-0x1c(%rbp)
cmp    $0x0,%eax
setg   %al
mov    %al,-0x1d(%rbp)
mov    -0x1d(%rbp),%al
test   $0x1,%al
jne    116f <read_size+0x5f>
jmp    117d <read_size+0x6d>
mov    -0x1c(%rbp),%eax
add    -0x18(%rbp),%eax
mov    %eax,-0x18(%rbp)
jmp    1129 <read_size+0x19>
mov    -0x18(%rbp),%eax
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<read_size>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
test   %edx,%edx
jle    114f <read_size+0x3f>
mov    %edx,%ebp
mov    %rsi,%r14
mov    %edi,%r15d
xor    %ebx,%ebx
cs nopw 0x0(%rax,%rax,1)
nop
movslq %ebx,%rax
lea    (%r14,%rax,1),%rsi
mov    %ebp,%edx
sub    %eax,%edx
mov    %r15d,%edi
call   1030 <read@plt>
test   %eax,%eax
jle    1151 <read_size+0x41>
add    %eax,%ebx
cmp    %ebp,%ebx
jl     1130 <read_size+0x20>
jmp    1151 <read_size+0x41>
xor    %ebx,%ebx
mov    %ebx,%eax
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret

LLVM IR (-O0):
define i32 @read_size(i32 %0, i8* %1, i32 %2) {
%4 = alloca i32
%5 = alloca i8*
%6 = alloca i32
%7 = alloca i32
%8 = alloca i32
store i32 %0, i32* %4
store i8* %1, i8** %5
store i32 %2, i32* %6
store i32 0, i32* %7
br label %9
9: ; preds = %26, %3
%10 = load i32, i32* %7
%11 = load i32, i32* %6
%12 = icmp slt i32 %10, %11
br i1 %12, label %13, label %24
13: ; preds = %9
%14 = load i32, i32* %4
%15 = load i8*, i8** %5
%16 = load i32, i32* %7
%17 = sext i32 %16 to i64
%18 = getelementptr inbounds i8, i8* %15, i64 %17
%19 = load i32, i32* %6
%20 = load i32, i32* %7
%21 = sub nsw i32 %19, %20
%22 = call i32 @read(i32 %14, i8* %18, i32 %21)
store i32 %22, i32* %8
%23 = icmp sgt i32 %22, 0
br label %24
24: ; preds = %13, %9
%25 = phi i1 [ false, %9 ], [ %23, %13 ]
br i1 %25, label %26, label %30
26: ; preds = %24
%27 = load i32, i32* %8
%28 = load i32, i32* %7
%29 = add nsw i32 %28, %27
store i32 %29, i32* %7
br label %9
30: ; preds = %24
%31 = load i32, i32* %7
ret i32 %31
}

LLVM IR (-O2):
define i32 @read_size(i32 %0, i8* nocapture %1, i32 %2) {
%4 = icmp sgt i32 %2, 0
br i1 %4, label %7, label %15
5: ; preds = %7
%6 = icmp slt i32 %14, %2
br i1 %6, label %7, label %15
7: ; preds = %3, %5
%8 = phi i32 [ %14, %5 ], [ 0, %3 ]
%9 = sext i32 %8 to i64
%10 = getelementptr inbounds i8, i8* %1, i64 %9
%11 = sub nsw i32 %2, %8
%12 = tail call i32 @read(i32 %0, i8* %10, i32 %11)
%13 = icmp sgt i32 %12, 0
%14 = add nsw i32 %12, %8
br i1 %13, label %5, label %15
15: ; preds = %7, %5, %3
%16 = phi i32 [ 0, %3 ], [ %14, %5 ], [ %8, %7 ]
ret i32 %16
}