ARM64: Optimize overflow and divbyzero checks with assertions

[EgorBo]

Closes #98100

static int Test(int a, int b)
{
    if (b <= 0)  // or other types of similar checks e.g. !=0 or throwing a user exception, etc..
        return 0;

    return a / b;
}

Codegen diff:

; Method Prog:Test(int,int):int (FullOpts)
G_M31864_IG01:
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp
G_M31864_IG02:
            cmp     w1, #0
            bgt     G_M31864_IG05
G_M31864_IG03:
            mov     w0, wzr
G_M31864_IG04:
            ldp     fp, lr, [sp], #0x10
            ret     lr
G_M31864_IG05:
-           cmp     w1, #0
-           beq     G_M31864_IG08
-           cmn     w1, #1
-           bne     G_M31864_IG06
-           cmp     w0, #1
-           bvs     G_M31864_IG09
+           sdiv    w0, w0, w1
G_M31864_IG06:
-           sdiv    w0, w0, w1
-G_M31864_IG07:
            ldp     fp, lr, [sp], #0x10
            ret     lr
-G_M31864_IG08:
-           bl      CORINFO_HELP_THROWDIVZERO
-G_M31864_IG09:
-           bl      CORINFO_HELP_OVERFLOW
-           brk_windows #0
-; Total bytes of code: 76
+; Total bytes of code: 40

Should slightly improve certain patterns on x64 as well.

[ghost]

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Issue Details

---

Closes #98100

static int Test(int a, int b)
{
    if (b <= 0)  // or other types of similar checks e.g. !=0 or throwing a user exception, etc..
        return 0;

    return a / b;
}

Codegen diff:

; Method Prog:Test(int,int):int (FullOpts)
G_M31864_IG01:
            stp     fp, lr, [sp, #-0x10]!
            mov     fp, sp
G_M31864_IG02:
            cmp     w1, #0
            bgt     G_M31864_IG05
G_M31864_IG03:
            mov     w0, wzr
G_M31864_IG04:
            ldp     fp, lr, [sp], #0x10
            ret     lr
G_M31864_IG05:
-           cmp     w1, #0
-           beq     G_M31864_IG08
-           cmn     w1, #1
-           bne     G_M31864_IG06
-           cmp     w0, #1
-           bvs     G_M31864_IG09
+           sdiv    w0, w0, w1
G_M31864_IG06:
-           sdiv    w0, w0, w1
-G_M31864_IG07:
            ldp     fp, lr, [sp], #0x10
            ret     lr
-G_M31864_IG08:
-           bl      CORINFO_HELP_THROWDIVZERO
-G_M31864_IG09:
-           bl      CORINFO_HELP_OVERFLOW
-           brk_windows #0
-; Total bytes of code: 76
+; Total bytes of code: 40

Author:	EgorBo
Assignees:	EgorBo
Labels:	area-CodeGen-coreclr
Milestone:	-

[EgorBo]

On x64 it helps by removing side-effects from divisions, e.g.:

if (b > 0)
{
    var unused = a / b;
}

this can be safely removed now while previously we had to preserve it due to possible exceptions.

[EgorBo]

@AndyAyersMS @dotnet/jit-contrib PTAL, a simple change, follow up to #94347 you reviewed. Diffs aren't too big, but I noticed that assertions quite often give up when a tree is wrapped in a cast - so hopefully diffs will improve once I improve that.

Also, it fixes potential problems from existing GTF_DIV_* flags.

[AndyAyersMS]

LGTM.

We might be able to catch some of these earlier. Feel free to address in a follow-up, if you like.