[llvm] [llvm][ARM]Add widen global arrays pass (PR #107120)

[Nashe Mncube via llvm-commits]

nasherm wrote:

> With the now updated pass I get the following output on the below (truncated) IR
> 
> **IR**
> 
> ```
> @.str = private unnamed_addr constant [10 x i8] c"123456789\00", align 1
> 
> ; Function Attrs: nounwind
> define hidden void @foo() #0 {
> entry:
>   %something = alloca [10 x i8], align 1
>   call void @llvm.memcpy.p0.p0.i32(ptr noundef nonnull align 1 dereferenceable(10) %something, ptr noundef nonnull align 1 dereferenceable(10) @.str, i32 10, i1 false)
>   %call2 = call i32 @bar(ptr nonnull %something)
>   ret void
> }
> 
> 
> declare i32 @bar(...)
> ```

***ARM***
```
**ARM (No pass)** 
```
$ opt -mtriple=arm-none-eabi -S | llc  -o -
foo:
	.fnstart
@ %bb.0:                                @ %entry
	.save	{r11, lr}
	push	{r11, lr}
	.pad	#16
	sub	sp, sp, #16
	mov	r0, #57
	strh	r0, [sp, #12]
	ldr	r0, .LCPI0_0
	str	r0, [sp, #8]
	ldr	r0, .LCPI0_1
	str	r0, [sp, #4]
	add	r0, sp, #4
	bl	bar
	add	sp, sp, #16
	pop	{r11, lr}
	mov	pc, lr
	.p2align	2
@ %bb.1:
.LCPI0_0:
	.long	943142453                       @ 0x38373635
.LCPI0_1:
	.long	875770417                       @ 0x34333231
.Lfunc_end0:
	.size	foo, .Lfunc_end0-foo
	.fnend
                                        @ -- End function
	.type	.L.str,%object                  @ @.str
	.section	.rodata.str1.4,"aMS",%progbits,1
	.p2align	2, 0x0
.L.str:
	.asciz	"123456789"
	.size	.L.str, 10

	.section	".note.GNU-stack","",%progbits
	.eabi_attribute	30, 1	@ Tag_ABI_optimization_goals

```

**ARM (with pass)**
```
$ opt -passes=globalopt -mtriple=arm-none-eabi -S | llc  -o -
foo:
	.fnstart
@ %bb.0:                                @ %entry
	.save	{r11, lr}
	push	{r11, lr}
	.pad	#16
	sub	sp, sp, #16
	mov	r0, #57
	str	r0, [sp, #12]
	ldr	r0, .LCPI0_0
	str	r0, [sp, #8]
	ldr	r0, .LCPI0_1
	str	r0, [sp, #4]
	add	r0, sp, #4
	bl	bar
	add	sp, sp, #16
	pop	{r11, lr}
	mov	pc, lr
	.p2align	2
@ %bb.1:
.LCPI0_0:
	.long	943142453                       @ 0x38373635
.LCPI0_1:
	.long	875770417                       @ 0x34333231
.Lfunc_end0:
	.size	foo, .Lfunc_end0-foo
	.fnend
                                        @ -- End function
	.type	.L.str,%object                  @ @.str
	.section	.rodata,"a",%progbits
	.p2align	2, 0x0
.L.str:
	.asciz	"123456789\000\000"
	.size	.L.str, 12

	.section	".note.GNU-stack","",%progbits
	.eabi_attribute	30, 1	@ Tag_ABI_optimization_goals
```

https://github.com/llvm/llvm-project/pull/107120