Patterns

extra b/nop

348:    bne     t8,at,380 ~>                      i 348:    bne     t8,at,378 ~>
34c:    nop                                         34c:    nop
350:    b       358 ~>                            <
354:    nop                                       <
358: ~> li      t9,0x20                             350:    li      t9,0x20
35c:    sh      t9,0x1c(sp)                         354:    sh      t9,0x1c(sp)
360:    lw      t0,0x2c(sp)                         358:    lw      t0,0x2c(sp)

This occurs when there is an if(0) {} statement with -g.

'arg0 + 0x10' when arg0 is a struct

func_8001C770(arg0 + 0x10);

becomes

func_8001C770(&arg0->unk10);

padded stacks

    u32 pad0;
    u8  pad1;
    u8  sp22;
    s8  sp21;
    s8  sp20;
    s32 sp1C;
    u16 pad2;
    s16 sp18;

    sp18 = 2;
    sp1C = 0;
    sp20 = arg1 | 0xB0;
    sp21 = 0xA;
    sp22 = arg2;

becomes (be aware of reversed ordering!)

typedef struct {
    s16 unk0;
    u16 unk2;
    s32 unk4;
    u8  unk8;
    u8  unk9;
    u8  unkA;
    u8  unkB;
    u32 unkC;
} struct33;

// <snip>
void func() {
    struct33 tmp;

    tmp.unk0 = 2;
    tmp.unk4 = 0;
    tmp.unk8 = arg1 | 0xB0;
    tmp.unk9 = 0xA;
    tmp.unkA = arg2;

// <snip>

missing arg0

void func_80009600(? arg1) {
    func_85161334(0xFF, 1);
}

becomes

void func_80009600(s32 arg0, s32 arg1) {
    func_85161334(arg0, 0xFF, 1);
}

crazy struct offset

    temp_a0 = ((D_800BE9F0 * 4) + 0x80090000)->unk1C04;

becomes

    temp_a0 = D_80091C04[D_800BE9F0]

crazy unrolling

s32 func_85004E00(void) {
    void *temp_v1;
    void *phi_v1;

    *(void *)0x800C6660 = 0;
    *(void *)0x800C6664 = 0;
    *(void *)0x800C6668 = 0;
    *(void *)0x800C666F = (u8)0;
    phi_v1 = (void *)0x800C6670;
loop_1:
    temp_v1 = phi_v1 + 0x40;
    temp_v1->unk-30 = 0;
    temp_v1->unk-2C = 0;
    temp_v1->unk-28 = 0;
    temp_v1->unk-21 = (u8)0;
    temp_v1->unk-20 = 0;
    temp_v1->unk-1C = 0;
    temp_v1->unk-18 = 0;
    temp_v1->unk-11 = (u8)0;
    temp_v1->unk-10 = 0;
    temp_v1->unk-C = 0;
    temp_v1->unk-8 = 0;
    temp_v1->unk-1 = (u8)0;
    temp_v1->unk-40 = 0;
    temp_v1->unk-3C = 0;
    temp_v1->unk-38 = 0;
    temp_v1->unk-31 = (u8)0;
    phi_v1 = temp_v1;
    if (temp_v1 != 0x800C67F0) {
        goto loop_1;
    }
    return 0x800C67F0;
}

becomes

void func_85004E00(void) {
    u32 i;

    for (i = 0; i < 25; i++)
    {
        D_800C6660[i].unk0 = 0;
        D_800C6660[i].unk4 = 0;
        D_800C6660[i].unk8 = 0;
        D_800C6660[i].unkF = 0;
    }
}

loops are bastards (1)

s32 func_86001B00(void *arg0) {
    s32 temp_v1;
    void *phi_v0;
    s32 phi_v1;
    s32 phi_v1_2;

    phi_v0 = arg0;
    phi_v1 = 0;
    phi_v1_2 = 0;
    if (*arg0 != 0) {
loop_1:
        temp_v1 = phi_v1_2 + 1;
        phi_v0 = phi_v0 + 1;
        phi_v1 = temp_v1;
        phi_v1_2 = temp_v1;
        if (phi_v0->unk1 != 0) {
            goto loop_1;
        }
    }
    return phi_v1;
}

becomes

u32 func_86001B00(u8 *arg0) {
    u32 i = 0;
    while (arg0[i]) {
        i++;
    };
    return i;
}

loops are bastards (2)

void *func_86001AD0(void *arg0, void *arg1, s32 arg2) {
    s32 temp_a2;
    void *temp_v0;
    void *phi_v1;
    void *phi_v0;
    s32 phi_a2;

    phi_v1 = arg1;
    phi_v0 = arg0;
    phi_a2 = arg2;
    if (arg2 != 0) {
loop_1:
        temp_a2 = phi_a2 - 1;
        temp_v0 = phi_v0 + 1;
        temp_v0->unk-1 = (u8) *phi_v1;
        phi_v1 = phi_v1 + 1;
        phi_v0 = temp_v0;
        phi_a2 = temp_a2;
        if (temp_a2 != 0) {
            goto loop_1;
        }
    }
    return arg0;
}

becomes

u8* func_86001AD0(u8 *arg0, u8 *arg1, u32 arg2) {
    u8 *tmp0 = arg0;
    u8 *tmp1 = arg1;

    while (arg2 > 0)
    {
        *tmp0++ = *tmp1++;
        arg2 -= 1;
    }

    return arg0;
}

loops can look worse than they are

When the condition is checking for an address, often subtracting the start from the end and dividing by the size of the array type gets you to a more sane place:

    phi_v1 = (void *)0x800DF7C8;
loop_1:
    temp_v1 = phi_v1 + 4;
    temp_v1->unk-4 = 0;
    phi_v1 = temp_v1;
    if (temp_v1 != 0x800DF7D0) {
        goto loop_1;
    }

becomes

    for (i = 0; i < 2; i++)
    {
        D_800DF7C8[i] = 0;
    }

temp_f6 + 4294967296.0f;

    if ((s32) temp_t8 < 0) {
        phi_f6 = temp_f6 + 4294967296.0f;
    }

just remove these statements

2D arrays

temp_v0 = (arg8 * 0x348) + (arg7 * 0x54) + 0x803F6720;

becomes

struct048 *temp_v0 = &D_803F6720[arg8][arg7];

where struct048 is size 0x54 and D_803F6720 is defined as extern struct048 D_803F6720[][10]