Compiler Optimization Question

compile-all.sh

#!/bin/bash

mkdir normalBin
mkdir weirdBin

g++ -Wall -std=c++14 -O0 -S -o normalBin/normal-O0.s normal.cpp
g++ -Wall -std=c++14 -O1 -S -o normalBin/normal-O1.s normal.cpp
g++ -Wall -std=c++14 -O2 -S -o normalBin/normal-O2.s normal.cpp
g++ -Wall -std=c++14 -O3 -S -o normalBin/normal-O3.s normal.cpp
g++ -Wall -std=c++14 -Ofast -S -o normalBin/normal-Ofast.s normal.cpp
g++ -Wall -std=c++14 -Os -S -o normalBin/normal-Os.s normal.cpp

g++ -Wall -std=c++14 -O0 -S -o weirdBin/weird-O0.s weird.cpp
g++ -Wall -std=c++14 -O1 -S -o weirdBin/weird-O1.s weird.cpp
g++ -Wall -std=c++14 -O2 -S -o weirdBin/weird-O2.s weird.cpp
g++ -Wall -std=c++14 -O3 -S -o weirdBin/weird-O3.s weird.cpp
g++ -Wall -std=c++14 -Ofast -S -o weirdBin/weird-Ofast.s weird.cpp
g++ -Wall -std=c++14 -Os -S -o weirdBin/weird-Os.s weird.cpp

normal-O0.s

	.file "normal.cpp"
	.def __main; .scl 2; .type 32; .endef
	.text
	.global main
	.def main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	pushq	%rbp
	.seh_pushreg	%rbp
	movq	%rsp, %rbp
	.seh_setframe	%rbp, 0
	subq	$32, %rsp
	.seh_stackalloc	32
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal-O1.s

	.file	"normal.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.text
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal-O2.s

	.file	"normal.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal-O3.s

	.file	"normal.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal-Ofast.s

	.file	"normal.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal-Os.s

	.file	"normal.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB0:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

normal.cpp

int main()
{
    while (true) {    }
    return 0;
}

weird-O0.s

	.file	"weird.cpp"
	.section	.text$_ZN9EventLoop13movementStateEv,"x"
	.linkonce discard
	.align 2
	.globl	_ZN9EventLoop13movementStateEv
	.def	_ZN9EventLoop13movementStateEv;	.scl	2;	.type	32;	.endef
	.seh_proc	_ZN9EventLoop13movementStateEv
_ZN9EventLoop13movementStateEv:
.LFB0:
	pushq	%rbp
	.seh_pushreg	%rbp
	movq	%rsp, %rbp
	.seh_setframe	%rbp, 0
	.seh_endprologue
	movq	%rcx, 16(%rbp)
	movl	$0, %eax
	popq	%rbp
	ret
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.def	__main;	.scl	2;	.type	32;	.endef
	.text
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	pushq	%rbp
	.seh_pushreg	%rbp
	movq	%rsp, %rbp
	.seh_setframe	%rbp, 0
	subq	$32, %rsp
	.seh_stackalloc	32
	.seh_endprologue
	call	__main
.L5:
	leaq	Pigs(%rip), %rcx
	call	_ZN9EventLoop13movementStateEv
	cmpl	$3, %eax
	setne	%al
	testb	%al, %al
	je	.L4
	jmp	.L5
.L4:
	movl	$0, %eax
	addq	$32, %rsp
	popq	%rbp
	ret
	.seh_endproc
	.ident	"GCC: (GNU) 5.4.0"

weird-O1.s

	.file	"weird.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.text
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.ident	"GCC: (GNU) 5.4.0"

weird-O2.s

	.file	"weird.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.ident	"GCC: (GNU) 5.4.0"

weird-O3.s

	.file	"weird.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.ident	"GCC: (GNU) 5.4.0"

weird-Ofast.s

	.file	"weird.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.p2align 4,,15
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.ident	"GCC: (GNU) 5.4.0"

weird-Os.s

	.file	"weird.cpp"
	.def	__main;	.scl	2;	.type	32;	.endef
	.section	.text.startup,"x"
	.globl	main
	.def	main;	.scl	2;	.type	32;	.endef
	.seh_proc	main
main:
.LFB1:
	subq	$40, %rsp
	.seh_stackalloc	40
	.seh_endprologue
	call	__main
.L2:
	jmp	.L2
	.seh_endproc
	.globl	Pigs
	.bss
Pigs:
	.space 1
	.ident	"GCC: (GNU) 5.4.0"

weird.cpp

enum class MovementState {
    Walking,
    Running,
    Swimming,
    Flying
};

struct EventLoop {
    MovementState movementState() {return MovementState::Walking;}
};

EventLoop Pigs;

int main()
{
    while (Pigs.movementState() != MovementState::Flying) { }
    return 0;
}