#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 /*<<< orphan*/ perror(char *);
int read(int, char *, int);
void readdata(int fd, char *b, int n) {
  int i, j;
  for (i = 0; i < n; i += j) {
    j = read(fd, b + i, n - i);
    if (j < 0) {
      perror("Error reading data");
      return;
    };
  }
}


x86 assembly (clang, -O0):
<readdata>:
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),%eax
cmp    -0x14(%rbp),%eax
jge    118f <readdata+0x6f>
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)
cmpl   $0x0,-0x1c(%rbp)
jge    117c <readdata+0x5c>
lea    0xe8e(%rip),%rdi
call   1040 <perror@plt>
jmp    118f <readdata+0x6f>
jmp    1181 <readdata+0x61>
mov    -0x1c(%rbp),%eax
add    -0x18(%rbp),%eax
mov    %eax,-0x18(%rbp)
jmp    1139 <readdata+0x19>
add    $0x20,%rsp
pop    %rbp
ret

x86 assembly (clang, -O2):
<readdata>:
push   %rbp
push   %r15
push   %r14
push   %rbx
push   %rax
test   %edx,%edx
jle    115d <readdata+0x3d>
mov    %edx,%ebx
mov    %rsi,%r14
mov    %edi,%r15d
xor    %ebp,%ebp
cs nopw 0x0(%rax,%rax,1)
nop
movslq %ebp,%rax
lea    (%r14,%rax,1),%rsi
mov    %ebx,%edx
sub    %eax,%edx
mov    %r15d,%edi
call   1030 <read@plt>
test   %eax,%eax
js     1168 <readdata+0x48>
add    %eax,%ebp
cmp    %ebx,%ebp
jl     1140 <readdata+0x20>
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
ret
lea    0xe91(%rip),%rdi
add    $0x8,%rsp
pop    %rbx
pop    %r14
pop    %r15
pop    %rbp
jmp    1040 <perror@plt>

LLVM IR (-O0):
@.str = [19 x i8] c"Error reading data\00"
define void @readdata(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 = %28, %3
%10 = load i32, i32* %7
%11 = load i32, i32* %6
%12 = icmp slt i32 %10, %11
br i1 %12, label %13, label %32
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 = load i32, i32* %8
%24 = icmp slt i32 %23, 0
br i1 %24, label %25, label %27
25: ; preds = %13
%26 = call i32 @perror(i8* getelementptr inbounds ([19 x i8], [19 x i8]* @.str, i64 0, i64 0))
br label %32
27: ; preds = %13
br label %28
28: ; preds = %27
%29 = load i32, i32* %8
%30 = load i32, i32* %7
%31 = add nsw i32 %30, %29
store i32 %31, i32* %7
br label %9
32: ; preds = %25, %9
ret void
}

LLVM IR (-O2):
@.str = [19 x i8] c"Error reading data\00"
define void @readdata(i32 %0, i8* nocapture %1, i32 %2) {
%4 = icmp sgt i32 %2, 0
br i1 %4, label %7, label %17
5: ; preds = %7
%6 = icmp slt i32 %14, %2
br i1 %6, label %7, label %17
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 slt i32 %12, 0
%14 = add nsw i32 %12, %8
br i1 %13, label %15, label %5
15: ; preds = %7
%16 = tail call i32 @perror(i8* getelementptr inbounds ([19 x i8], [19 x i8]* @.str, i64 0, i64 0))
br label %17
17: ; preds = %5, %3, %15
ret void
}