gistfile1.txt

$ cat /tmp/combine.ll 

; ModuleID = '<stdin>'
source_filename = "pg"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-pc-linux-gnu"

define void @evalexpr_0_0(i8* align 8 noalias, i32* align 8 noalias) {
entry:
  %a01 = getelementptr i8, i8* %0, i16 0
  store i8 0, i8* %a01

  ; in the real case this also loads data
  %b01 = getelementptr i32, i32* %1, i16 0
  store i32 0, i32* %b01

  %a02 = getelementptr i8, i8* %0, i16 1
  store i8 0, i8* %a02

  ; in the real case this also loads data
  %b02 = getelementptr i32, i32* %1, i16 1
  store i32 0, i32* %b02

  ; in the real case this also loads data
  %a03 = getelementptr i8, i8* %0, i16 2
  store i8 0, i8* %a03

  ; in the real case this also loads data
  %b03 = getelementptr i32, i32* %1, i16 2
  store i32 0, i32* %b03

  %a04 = getelementptr i8, i8* %0, i16 3
  store i8 0, i8* %a04

  ; in the real case this also loads data
  %b04 = getelementptr i32, i32* %1, i16 3
  store i32 0, i32* %b04

  ret void
}

$ opt -disable-slp-vectorization -O3 -S /tmp/combine.ll |llc -O3|less
        .text
        .file   "pg"
        .globl  evalexpr_0_0            # -- Begin function evalexpr_0_0
        .p2align        4, 0x90
        .type   evalexpr_0_0,@function
evalexpr_0_0:                           # @evalexpr_0_0
# %bb.0:                                # %entry
        movb    $0, (%rdi)
        movl    $0, (%rsi)
        movb    $0, 1(%rdi)
        movl    $0, 4(%rsi)
        movb    $0, 2(%rdi)
        movl    $0, 8(%rsi)
        movb    $0, 3(%rdi)
        movl    $0, 12(%rsi)
        retq
.Lfunc_end0:
        .size   evalexpr_0_0, .Lfunc_end0-evalexpr_0_0
                                        # -- End function

        .section        ".note.GNU-stack","",@progbits


$ opt -O3 -S /tmp/combine.ll |llc -O3|less
        .text
        .file   "pg"
        .globl  evalexpr_0_0            # -- Begin function evalexpr_0_0
        .p2align        4, 0x90
        .type   evalexpr_0_0,@function
evalexpr_0_0:                           # @evalexpr_0_0
# %bb.0:                                # %entry
        movl    $0, (%rdi)
        xorps   %xmm0, %xmm0
        movups  %xmm0, (%rsi)
        retq
.Lfunc_end0:
        .size   evalexpr_0_0, .Lfunc_end0-evalexpr_0_0
                                        # -- End function

        .section        ".note.GNU-stack","",@progbits