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Comparison of Assembly across five architectures
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gcc-asm-notes.md

Blog 2020/1/27

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Comparison of Assembly across five architectures

I've been cobbling together a little collection of architectures as part of my journey to learn how to write a compiler.

  • x86_64:
    • Linux buster 4.19.0-6-amd64 #1 SMP Debian 4.19.67-2 (2019-08-28) x86_64 GNU/Linux
  • i586:
    • Linux pic 3.16.0-10-586 #1 Debian 3.16.72-1 (2019-08-13) i586 GNU/Linux
  • ARM 5:
    • Linux pogo 3.18.5-kirkwood-tld-1 #1 PREEMPT Thu Feb 5 17:58:07 PST 2015 armv5tel GNU/Linux
    • (actually, Debian's armel produces armv4t)
  • PowerPC:
    • Linux emac 5.3.0-3-powerpc #1 Debian 5.3.15-1 (2019-12-07) ppc GNU/Linux
  • MIPS:
    • Linux ci20 3.18.3-ci20-1 #1 SMP PREEMPT Wed May 25 10:24:41 UTC 2016 mips GNU/Linux

This blog post contains gcc's assembly output for a series of simple C programs.

I've also included LLVM IR output from clang.

Program 1: return a constant

int main() {
	return 42;
}

gcc-4.8 -std=c99 -O0 -S main42.c

x86_64

	.file	"main42.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movl	$42, %eax
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

i586

	.file	"main42.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	movl	$42, %eax
	popl	%ebp
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

armv5tel

	.arch armv4t
	.fpu softvfp
	.eabi_attribute 20, 1
	.eabi_attribute 21, 1
	.eabi_attribute 23, 3
	.eabi_attribute 24, 1
	.eabi_attribute 25, 1
	.eabi_attribute 26, 2
	.eabi_attribute 30, 6
	.eabi_attribute 34, 0
	.eabi_attribute 18, 4
	.file	"main42.c"
	.text
	.align	2
	.global	main
	.type	main, %function
main:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 0
	@ frame_needed = 1, uses_anonymous_args = 0
	@ link register save eliminated.
	str	fp, [sp, #-4]!
	add	fp, sp, #0
	mov	r3, #42
	mov	r0, r3
	sub	sp, fp, #0
	@ sp needed
	ldr	fp, [sp], #4
	bx	lr
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",%progbits

ppc

	.file	"main42.c"
	.section	".text"
	.align 2
	.globl main
	.type	main, @function
main:
	stwu 1,-16(1)
	stw 31,12(1)
	mr 31,1
	li 9,42
	mr 3,9
	addi 11,31,16
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	main,.-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

mips

	.file	1 "main42.c"
	.section .mdebug.abi32
	.previous
	.gnu_attribute 4, 1
	.abicalls
	.text
	.align	2
	.globl	main
	.set	nomips16
	.ent	main
	.type	main, @function
main:
	.frame	$fp,8,$31		# vars= 0, regs= 1/0, args= 0, gp= 0
	.mask	0x40000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-8
	sw	$fp,4($sp)
	move	$fp,$sp
	li	$2,42			# 0x2a
	move	$sp,$fp
	lw	$fp,4($sp)
	addiu	$sp,$sp,8
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	main
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"

LLVM IR

clang-3.5 -std=c99 -O0 -S -emit-llvm main42.c

; ModuleID = 'main42.c'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nounwind uwtable
define i32 @main() #0 {
  %1 = alloca i32, align 4
  store i32 0, i32* %1
  ret i32 42
}

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }

!llvm.ident = !{!0}

!0 = metadata !{metadata !"Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)"}

Program 2: add two integers

#include <stdlib.h>

int main(int argc, char** argv) {
	return atoi(argv[1]) + atoi(argv[2]);
}

gcc-4.8 -std=c99 -O0 -S plus.c

x86_64

	.file	"plus.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	pushq	%rbx
	subq	$24, %rsp
	.cfi_offset 3, -24
	movl	%edi, -20(%rbp)
	movq	%rsi, -32(%rbp)
	movq	-32(%rbp), %rax
	addq	$8, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	movl	%eax, %ebx
	movq	-32(%rbp), %rax
	addq	$16, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	addl	%ebx, %eax
	addq	$24, %rsp
	popq	%rbx
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

i586

	.file	"plus.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	pushl	%ebx
	andl	$-16, %esp
	subl	$16, %esp
	.cfi_offset 3, -12
	movl	12(%ebp), %eax
	addl	$4, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	movl	%eax, %ebx
	movl	12(%ebp), %eax
	addl	$8, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	addl	%ebx, %eax
	movl	-4(%ebp), %ebx
	leave
	.cfi_restore 5
	.cfi_restore 3
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

armv5tel

	.arch armv4t
	.fpu softvfp
	.eabi_attribute 20, 1
	.eabi_attribute 21, 1
	.eabi_attribute 23, 3
	.eabi_attribute 24, 1
	.eabi_attribute 25, 1
	.eabi_attribute 26, 2
	.eabi_attribute 30, 6
	.eabi_attribute 34, 0
	.eabi_attribute 18, 4
	.file	"plus.c"
	.text
	.align	2
	.global	main
	.type	main, %function
main:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 8
	@ frame_needed = 1, uses_anonymous_args = 0
	stmfd	sp!, {r4, fp, lr}
	add	fp, sp, #8
	sub	sp, sp, #12
	str	r0, [fp, #-16]
	str	r1, [fp, #-20]
	ldr	r3, [fp, #-20]
	add	r3, r3, #4
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	mov	r4, r0
	ldr	r3, [fp, #-20]
	add	r3, r3, #8
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	mov	r3, r0
	add	r3, r4, r3
	mov	r0, r3
	sub	sp, fp, #8
	@ sp needed
	ldmfd	sp!, {r4, fp, lr}
	bx	lr
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",%progbits

ppc

	.file	"plus.c"
	.section	".text"
	.align 2
	.globl main
	.type	main, @function
main:
	stwu 1,-32(1)
	mflr 0
	stw 0,36(1)
	stw 30,24(1)
	stw 31,28(1)
	mr 31,1
	stw 3,8(31)
	stw 4,12(31)
	lwz 9,12(31)
	addi 9,9,4
	lwz 9,0(9)
	mr 3,9
	bl atoi
	mr 30,3
	lwz 9,12(31)
	addi 9,9,8
	lwz 9,0(9)
	mr 3,9
	bl atoi
	mr 9,3
	add 9,30,9
	mr 3,9
	addi 11,31,32
	lwz 0,4(11)
	mtlr 0
	lwz 30,-8(11)
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	main,.-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

mips

	.file	1 "plus.c"
	.section .mdebug.abi32
	.previous
	.gnu_attribute 4, 1
	.abicalls
	.text
	.align	2
	.globl	main
	.set	nomips16
	.ent	main
	.type	main, @function
main:
	.frame	$fp,40,$31		# vars= 0, regs= 3/0, args= 16, gp= 8
	.mask	0xc0010000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-40
	sw	$31,36($sp)
	sw	$fp,32($sp)
	sw	$16,28($sp)
	move	$fp,$sp
	lui	$28,%hi(__gnu_local_gp)
	addiu	$28,$28,%lo(__gnu_local_gp)
	.cprestore	16
	sw	$4,40($fp)
	sw	$5,44($fp)
	lw	$2,44($fp)
	addiu	$2,$2,4
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	move	$16,$2
	lw	$2,44($fp)
	addiu	$2,$2,8
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	addu	$2,$16,$2
	move	$sp,$fp
	lw	$31,36($sp)
	lw	$fp,32($sp)
	lw	$16,28($sp)
	addiu	$sp,$sp,40
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	main
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"

LLVM IR

clang-3.5 -std=c99 -O0 -S -emit-llvm plus.c

; ModuleID = 'plus.c'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nounwind uwtable
define i32 @main(i32 %argc, i8** %argv) #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i8**, align 8
  store i32 0, i32* %1
  store i32 %argc, i32* %2, align 4
  store i8** %argv, i8*** %3, align 8
  %4 = load i8*** %3, align 8
  %5 = getelementptr inbounds i8** %4, i64 1
  %6 = load i8** %5, align 8
  %7 = call i32 @atoi(i8* %6) #2
  %8 = load i8*** %3, align 8
  %9 = getelementptr inbounds i8** %8, i64 2
  %10 = load i8** %9, align 8
  %11 = call i32 @atoi(i8* %10) #2
  %12 = add nsw i32 %7, %11
  ret i32 %12
}

; Function Attrs: nounwind readonly
declare i32 @atoi(i8*) #1

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind readonly }

!llvm.ident = !{!0}

!0 = metadata !{metadata !"Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)"}

Program 3: looping

#include <stdlib.h>

int main(int argc, char** argv) {
	int accum = 0;
	int i = atoi(argv[1]);
	while (i > 0) {
		accum += 1;
		i -= 1;
	}
	return accum;
}

gcc-4.8 -std=c99 -O0 -S loop.c

x86_64

	.file	"loop.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$32, %rsp
	movl	%edi, -20(%rbp)
	movq	%rsi, -32(%rbp)
	movl	$0, -4(%rbp)
	movq	-32(%rbp), %rax
	addq	$8, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	movl	%eax, -8(%rbp)
	jmp	.L2
.L3:
	addl	$1, -4(%rbp)
	subl	$1, -8(%rbp)
.L2:
	cmpl	$0, -8(%rbp)
	jg	.L3
	movl	-4(%rbp), %eax
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

i586

	.file	"loop.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	andl	$-16, %esp
	subl	$32, %esp
	movl	$0, 28(%esp)
	movl	12(%ebp), %eax
	addl	$4, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	movl	%eax, 24(%esp)
	jmp	.L2
.L3:
	addl	$1, 28(%esp)
	subl	$1, 24(%esp)
.L2:
	cmpl	$0, 24(%esp)
	jg	.L3
	movl	28(%esp), %eax
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

armv5tel

	.arch armv4t
	.fpu softvfp
	.eabi_attribute 20, 1
	.eabi_attribute 21, 1
	.eabi_attribute 23, 3
	.eabi_attribute 24, 1
	.eabi_attribute 25, 1
	.eabi_attribute 26, 2
	.eabi_attribute 30, 6
	.eabi_attribute 34, 0
	.eabi_attribute 18, 4
	.file	"loop.c"
	.text
	.align	2
	.global	main
	.type	main, %function
main:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 16
	@ frame_needed = 1, uses_anonymous_args = 0
	stmfd	sp!, {fp, lr}
	add	fp, sp, #4
	sub	sp, sp, #16
	str	r0, [fp, #-16]
	str	r1, [fp, #-20]
	mov	r3, #0
	str	r3, [fp, #-8]
	ldr	r3, [fp, #-20]
	add	r3, r3, #4
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	str	r0, [fp, #-12]
	b	.L2
.L3:
	ldr	r3, [fp, #-8]
	add	r3, r3, #1
	str	r3, [fp, #-8]
	ldr	r3, [fp, #-12]
	sub	r3, r3, #1
	str	r3, [fp, #-12]
.L2:
	ldr	r3, [fp, #-12]
	cmp	r3, #0
	bgt	.L3
	ldr	r3, [fp, #-8]
	mov	r0, r3
	sub	sp, fp, #4
	@ sp needed
	ldmfd	sp!, {fp, lr}
	bx	lr
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",%progbits

ppc

	.file	"loop.c"
	.section	".text"
	.align 2
	.globl main
	.type	main, @function
main:
	stwu 1,-48(1)
	mflr 0
	stw 0,52(1)
	stw 31,44(1)
	mr 31,1
	stw 3,24(31)
	stw 4,28(31)
	li 9,0
	stw 9,8(31)
	lwz 9,28(31)
	addi 9,9,4
	lwz 9,0(9)
	mr 3,9
	bl atoi
	stw 3,12(31)
	b .L2
.L3:
	lwz 9,8(31)
	addi 9,9,1
	stw 9,8(31)
	lwz 9,12(31)
	addi 9,9,-1
	stw 9,12(31)
.L2:
	lwz 9,12(31)
	cmpwi 7,9,0
	bgt 7,.L3
	lwz 9,8(31)
	mr 3,9
	addi 11,31,48
	lwz 0,4(11)
	mtlr 0
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	main,.-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

mips

	.file	1 "loop.c"
	.section .mdebug.abi32
	.previous
	.gnu_attribute 4, 1
	.abicalls
	.text
	.align	2
	.globl	main
	.set	nomips16
	.ent	main
	.type	main, @function
main:
	.frame	$fp,40,$31		# vars= 8, regs= 2/0, args= 16, gp= 8
	.mask	0xc0000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-40
	sw	$31,36($sp)
	sw	$fp,32($sp)
	move	$fp,$sp
	lui	$28,%hi(__gnu_local_gp)
	addiu	$28,$28,%lo(__gnu_local_gp)
	.cprestore	16
	sw	$4,40($fp)
	sw	$5,44($fp)
	sw	$0,24($fp)
	lw	$2,44($fp)
	addiu	$2,$2,4
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	sw	$2,28($fp)
	.option	pic0
	j	$L2
	nop

	.option	pic2
$L3:
	lw	$2,24($fp)
	addiu	$2,$2,1
	sw	$2,24($fp)
	lw	$2,28($fp)
	addiu	$2,$2,-1
	sw	$2,28($fp)
$L2:
	lw	$2,28($fp)
	bgtz	$2,$L3
	nop

	lw	$2,24($fp)
	move	$sp,$fp
	lw	$31,36($sp)
	lw	$fp,32($sp)
	addiu	$sp,$sp,40
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	main
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"

LLVM IR

clang-3.5 -std=c99 -O0 -S -emit-llvm loop.c

; ModuleID = 'loop.c'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nounwind uwtable
define i32 @main(i32 %argc, i8** %argv) #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i8**, align 8
  %accum = alloca i32, align 4
  %i = alloca i32, align 4
  store i32 0, i32* %1
  store i32 %argc, i32* %2, align 4
  store i8** %argv, i8*** %3, align 8
  store i32 0, i32* %accum, align 4
  %4 = load i8*** %3, align 8
  %5 = getelementptr inbounds i8** %4, i64 1
  %6 = load i8** %5, align 8
  %7 = call i32 @atoi(i8* %6) #2
  store i32 %7, i32* %i, align 4
  br label %8

; <label>:8                                       ; preds = %11, %0
  %9 = load i32* %i, align 4
  %10 = icmp sgt i32 %9, 0
  br i1 %10, label %11, label %16

; <label>:11                                      ; preds = %8
  %12 = load i32* %accum, align 4
  %13 = add nsw i32 %12, 1
  store i32 %13, i32* %accum, align 4
  %14 = load i32* %i, align 4
  %15 = sub nsw i32 %14, 1
  store i32 %15, i32* %i, align 4
  br label %8

; <label>:16                                      ; preds = %8
  %17 = load i32* %accum, align 4
  ret i32 %17
}

; Function Attrs: nounwind readonly
declare i32 @atoi(i8*) #1

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind readonly }

!llvm.ident = !{!0}

!0 = metadata !{metadata !"Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)"}

Program 4: branching

#include <stdlib.h>

int main(int argc, char** argv) {
	if (atoi(argv[1])) {
		return 42;
	} else {
		return 24;
	}
}

gcc-4.8 -std=c99 -O0 -S if.c

x86_64

	.file	"if.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	subq	$16, %rsp
	movl	%edi, -4(%rbp)
	movq	%rsi, -16(%rbp)
	movq	-16(%rbp), %rax
	addq	$8, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	testl	%eax, %eax
	je	.L2
	movl	$42, %eax
	jmp	.L3
.L2:
	movl	$24, %eax
.L3:
	leave
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

i586

	.file	"if.c"
	.text
	.globl	main
	.type	main, @function
main:
.LFB0:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	andl	$-16, %esp
	subl	$16, %esp
	movl	12(%ebp), %eax
	addl	$4, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	testl	%eax, %eax
	je	.L2
	movl	$42, %eax
	jmp	.L3
.L2:
	movl	$24, %eax
.L3:
	leave
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

armv5tel

	.arch armv4t
	.fpu softvfp
	.eabi_attribute 20, 1
	.eabi_attribute 21, 1
	.eabi_attribute 23, 3
	.eabi_attribute 24, 1
	.eabi_attribute 25, 1
	.eabi_attribute 26, 2
	.eabi_attribute 30, 6
	.eabi_attribute 34, 0
	.eabi_attribute 18, 4
	.file	"if.c"
	.text
	.align	2
	.global	main
	.type	main, %function
main:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 8
	@ frame_needed = 1, uses_anonymous_args = 0
	stmfd	sp!, {fp, lr}
	add	fp, sp, #4
	sub	sp, sp, #8
	str	r0, [fp, #-8]
	str	r1, [fp, #-12]
	ldr	r3, [fp, #-12]
	add	r3, r3, #4
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	mov	r3, r0
	cmp	r3, #0
	beq	.L2
	mov	r3, #42
	b	.L3
.L2:
	mov	r3, #24
.L3:
	mov	r0, r3
	sub	sp, fp, #4
	@ sp needed
	ldmfd	sp!, {fp, lr}
	bx	lr
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",%progbits

ppc

	.file	"if.c"
	.section	".text"
	.align 2
	.globl main
	.type	main, @function
main:
	stwu 1,-32(1)
	mflr 0
	stw 0,36(1)
	stw 31,28(1)
	mr 31,1
	stw 3,8(31)
	stw 4,12(31)
	lwz 9,12(31)
	addi 9,9,4
	lwz 9,0(9)
	mr 3,9
	bl atoi
	mr 9,3
	cmpwi 7,9,0
	beq 7,.L2
	li 9,42
	b .L3
.L2:
	li 9,24
.L3:
	mr 3,9
	addi 11,31,32
	lwz 0,4(11)
	mtlr 0
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	main,.-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

mips

	.file	1 "if.c"
	.section .mdebug.abi32
	.previous
	.gnu_attribute 4, 1
	.abicalls
	.text
	.align	2
	.globl	main
	.set	nomips16
	.ent	main
	.type	main, @function
main:
	.frame	$fp,32,$31		# vars= 0, regs= 2/0, args= 16, gp= 8
	.mask	0xc0000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-32
	sw	$31,28($sp)
	sw	$fp,24($sp)
	move	$fp,$sp
	lui	$28,%hi(__gnu_local_gp)
	addiu	$28,$28,%lo(__gnu_local_gp)
	.cprestore	16
	sw	$4,32($fp)
	sw	$5,36($fp)
	lw	$2,36($fp)
	addiu	$2,$2,4
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	beq	$2,$0,$L2
	nop

	li	$2,42			# 0x2a
	.option	pic0
	j	$L3
	nop

	.option	pic2
$L2:
	li	$2,24			# 0x18
$L3:
	move	$sp,$fp
	lw	$31,28($sp)
	lw	$fp,24($sp)
	addiu	$sp,$sp,32
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	main
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"

LLVM IR

clang-3.5 -std=c99 -O0 -S -emit-llvm if.c

; ModuleID = 'if.c'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nounwind uwtable
define i32 @main(i32 %argc, i8** %argv) #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i8**, align 8
  store i32 0, i32* %1
  store i32 %argc, i32* %2, align 4
  store i8** %argv, i8*** %3, align 8
  %4 = load i8*** %3, align 8
  %5 = getelementptr inbounds i8** %4, i64 1
  %6 = load i8** %5, align 8
  %7 = call i32 @atoi(i8* %6) #2
  %8 = icmp ne i32 %7, 0
  br i1 %8, label %9, label %10

; <label>:9                                       ; preds = %0
  store i32 42, i32* %1
  br label %11

; <label>:10                                      ; preds = %0
  store i32 24, i32* %1
  br label %11

; <label>:11                                      ; preds = %10, %9
  %12 = load i32* %1
  ret i32 %12
}

; Function Attrs: nounwind readonly
declare i32 @atoi(i8*) #1

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind readonly }

!llvm.ident = !{!0}

!0 = metadata !{metadata !"Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)"}

Program 5: function call

#include <stdlib.h>

int addfunc(int a, int b) {
	return a + b;
}

int main(int argc, char** argv) {
	return addfunc(atoi(argv[1]), atoi(argv[2]));
}

gcc-4.8 -std=c99 -O0 -S func.c

x86_64

	.file	"func.c"
	.text
	.globl	addfunc
	.type	addfunc, @function
addfunc:
.LFB0:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	movl	%edi, -4(%rbp)
	movl	%esi, -8(%rbp)
	movl	-8(%rbp), %eax
	movl	-4(%rbp), %edx
	addl	%edx, %eax
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE0:
	.size	addfunc, .-addfunc
	.globl	main
	.type	main, @function
main:
.LFB1:
	.cfi_startproc
	pushq	%rbp
	.cfi_def_cfa_offset 16
	.cfi_offset 6, -16
	movq	%rsp, %rbp
	.cfi_def_cfa_register 6
	pushq	%rbx
	subq	$24, %rsp
	.cfi_offset 3, -24
	movl	%edi, -20(%rbp)
	movq	%rsi, -32(%rbp)
	movq	-32(%rbp), %rax
	addq	$16, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	movl	%eax, %ebx
	movq	-32(%rbp), %rax
	addq	$8, %rax
	movq	(%rax), %rax
	movq	%rax, %rdi
	call	atoi
	movl	%ebx, %esi
	movl	%eax, %edi
	call	addfunc
	addq	$24, %rsp
	popq	%rbx
	popq	%rbp
	.cfi_def_cfa 7, 8
	ret
	.cfi_endproc
.LFE1:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

i586

	.file	"func.c"
	.text
	.globl	addfunc
	.type	addfunc, @function
addfunc:
.LFB0:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	movl	12(%ebp), %eax
	movl	8(%ebp), %edx
	addl	%edx, %eax
	popl	%ebp
	.cfi_restore 5
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE0:
	.size	addfunc, .-addfunc
	.globl	main
	.type	main, @function
main:
.LFB1:
	.cfi_startproc
	pushl	%ebp
	.cfi_def_cfa_offset 8
	.cfi_offset 5, -8
	movl	%esp, %ebp
	.cfi_def_cfa_register 5
	pushl	%ebx
	andl	$-16, %esp
	subl	$16, %esp
	.cfi_offset 3, -12
	movl	12(%ebp), %eax
	addl	$8, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	movl	%eax, %ebx
	movl	12(%ebp), %eax
	addl	$4, %eax
	movl	(%eax), %eax
	movl	%eax, (%esp)
	call	atoi
	movl	%ebx, 4(%esp)
	movl	%eax, (%esp)
	call	addfunc
	movl	-4(%ebp), %ebx
	leave
	.cfi_restore 5
	.cfi_restore 3
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
.LFE1:
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

armv5tel

	.arch armv4t
	.fpu softvfp
	.eabi_attribute 20, 1
	.eabi_attribute 21, 1
	.eabi_attribute 23, 3
	.eabi_attribute 24, 1
	.eabi_attribute 25, 1
	.eabi_attribute 26, 2
	.eabi_attribute 30, 6
	.eabi_attribute 34, 0
	.eabi_attribute 18, 4
	.file	"func.c"
	.text
	.align	2
	.global	addfunc
	.type	addfunc, %function
addfunc:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 8
	@ frame_needed = 1, uses_anonymous_args = 0
	@ link register save eliminated.
	str	fp, [sp, #-4]!
	add	fp, sp, #0
	sub	sp, sp, #12
	str	r0, [fp, #-8]
	str	r1, [fp, #-12]
	ldr	r2, [fp, #-8]
	ldr	r3, [fp, #-12]
	add	r3, r2, r3
	mov	r0, r3
	sub	sp, fp, #0
	@ sp needed
	ldr	fp, [sp], #4
	bx	lr
	.size	addfunc, .-addfunc
	.align	2
	.global	main
	.type	main, %function
main:
	@ Function supports interworking.
	@ args = 0, pretend = 0, frame = 8
	@ frame_needed = 1, uses_anonymous_args = 0
	stmfd	sp!, {r4, fp, lr}
	add	fp, sp, #8
	sub	sp, sp, #12
	str	r0, [fp, #-16]
	str	r1, [fp, #-20]
	ldr	r3, [fp, #-20]
	add	r3, r3, #4
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	mov	r4, r0
	ldr	r3, [fp, #-20]
	add	r3, r3, #8
	ldr	r3, [r3]
	mov	r0, r3
	bl	atoi
	mov	r3, r0
	mov	r0, r4
	mov	r1, r3
	bl	addfunc
	mov	r3, r0
	mov	r0, r3
	sub	sp, fp, #8
	@ sp needed
	ldmfd	sp!, {r4, fp, lr}
	bx	lr
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",%progbits

ppc

	.file	"func.c"
	.section	".text"
	.align 2
	.globl addfunc
	.type	addfunc, @function
addfunc:
	stwu 1,-32(1)
	stw 31,28(1)
	mr 31,1
	stw 3,8(31)
	stw 4,12(31)
	lwz 10,8(31)
	lwz 9,12(31)
	add 9,10,9
	mr 3,9
	addi 11,31,32
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	addfunc,.-addfunc
	.align 2
	.globl main
	.type	main, @function
main:
	stwu 1,-32(1)
	mflr 0
	stw 0,36(1)
	stw 30,24(1)
	stw 31,28(1)
	mr 31,1
	stw 3,8(31)
	stw 4,12(31)
	lwz 9,12(31)
	addi 9,9,4
	lwz 9,0(9)
	mr 3,9
	bl atoi
	mr 30,3
	lwz 9,12(31)
	addi 9,9,8
	lwz 9,0(9)
	mr 3,9
	bl atoi
	mr 9,3
	mr 3,30
	mr 4,9
	bl addfunc
	mr 9,3
	mr 3,9
	addi 11,31,32
	lwz 0,4(11)
	mtlr 0
	lwz 30,-8(11)
	lwz 31,-4(11)
	mr 1,11
	blr
	.size	main,.-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"
	.section	.note.GNU-stack,"",@progbits

mips

	.file	1 "func.c"
	.section .mdebug.abi32
	.previous
	.gnu_attribute 4, 1
	.abicalls
	.text
	.align	2
	.globl	addfunc
	.set	nomips16
	.ent	addfunc
	.type	addfunc, @function
addfunc:
	.frame	$fp,8,$31		# vars= 0, regs= 1/0, args= 0, gp= 0
	.mask	0x40000000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-8
	sw	$fp,4($sp)
	move	$fp,$sp
	sw	$4,8($fp)
	sw	$5,12($fp)
	lw	$3,8($fp)
	lw	$2,12($fp)
	addu	$2,$3,$2
	move	$sp,$fp
	lw	$fp,4($sp)
	addiu	$sp,$sp,8
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	addfunc
	.size	addfunc, .-addfunc
	.align	2
	.globl	main
	.set	nomips16
	.ent	main
	.type	main, @function
main:
	.frame	$fp,40,$31		# vars= 0, regs= 3/0, args= 16, gp= 8
	.mask	0xc0010000,-4
	.fmask	0x00000000,0
	.set	noreorder
	.set	nomacro
	addiu	$sp,$sp,-40
	sw	$31,36($sp)
	sw	$fp,32($sp)
	sw	$16,28($sp)
	move	$fp,$sp
	lui	$28,%hi(__gnu_local_gp)
	addiu	$28,$28,%lo(__gnu_local_gp)
	.cprestore	16
	sw	$4,40($fp)
	sw	$5,44($fp)
	lw	$2,44($fp)
	addiu	$2,$2,4
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	move	$16,$2
	lw	$2,44($fp)
	addiu	$2,$2,8
	lw	$2,0($2)
	move	$4,$2
	lw	$2,%call16(atoi)($28)
	move	$25,$2
	jalr	$25
	nop

	lw	$28,16($fp)
	move	$4,$16
	move	$5,$2
	.option	pic0
	jal	addfunc
	nop

	.option	pic2
	lw	$28,16($fp)
	move	$sp,$fp
	lw	$31,36($sp)
	lw	$fp,32($sp)
	lw	$16,28($sp)
	addiu	$sp,$sp,40
	j	$31
	nop

	.set	macro
	.set	reorder
	.end	main
	.size	main, .-main
	.ident	"GCC: (Debian 4.8.4-1) 4.8.4"

LLVM IR

clang-3.5 -std=c99 -O0 -S -emit-llvm func.c

; ModuleID = 'func.c'
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

; Function Attrs: nounwind uwtable
define i32 @addfunc(i32 %a, i32 %b) #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  store i32 %a, i32* %1, align 4
  store i32 %b, i32* %2, align 4
  %3 = load i32* %1, align 4
  %4 = load i32* %2, align 4
  %5 = add nsw i32 %3, %4
  ret i32 %5
}

; Function Attrs: nounwind uwtable
define i32 @main(i32 %argc, i8** %argv) #0 {
  %1 = alloca i32, align 4
  %2 = alloca i32, align 4
  %3 = alloca i8**, align 8
  store i32 0, i32* %1
  store i32 %argc, i32* %2, align 4
  store i8** %argv, i8*** %3, align 8
  %4 = load i8*** %3, align 8
  %5 = getelementptr inbounds i8** %4, i64 1
  %6 = load i8** %5, align 8
  %7 = call i32 @atoi(i8* %6) #2
  %8 = load i8*** %3, align 8
  %9 = getelementptr inbounds i8** %8, i64 2
  %10 = load i8** %9, align 8
  %11 = call i32 @atoi(i8* %10) #2
  %12 = call i32 @addfunc(i32 %7, i32 %11)
  ret i32 %12
}

; Function Attrs: nounwind readonly
declare i32 @atoi(i8*) #1

attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #1 = { nounwind readonly "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
attributes #2 = { nounwind readonly }

!llvm.ident = !{!0}

!0 = metadata !{metadata !"Debian clang version 3.5.0-10 (tags/RELEASE_350/final) (based on LLVM 3.5.0)"}
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