[llvm-dev] SLP example not being vectorized

[Sandoval Gonzalez, Leonardo via llvm-dev]

Hi,

I am new to llvm with a particular interested in the optimization area, 
specially on SLP. While working through the tutorial, I ran this example 
[1] with the hope to see SLP vectorization in action but for some 
reason, I do not see it on the LLVM assembly as seen below. Is there 
anything I am missing? I am using Clearlinux as build machine and this 
has clang version 9.0.0.


---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

$ cat arraysum.c
void foo(int a1, int a2, int b1, int b2, int *A) {
   A[0] = a1*(a1 + b1)/b1 + 50*b1/a1;
   A[1] = a2*(a2 + b2)/b2 + 50*b2/a2;
}


$ clang -emit-llvm -S -O3 arraysum.c -o -
; ModuleID = 'arraysum.c'
source_filename = "arraysum.c"
target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-generic-linux"

; Function Attrs: nofree norecurse nounwind uwtable writeonly
define dso_local void @foo(i32, i32, i32, i32, i32* nocapture) 
local_unnamed_addr #0 {
   %6 = add nsw i32 %2, %0
   %7 = mul nsw i32 %6, %0
   %8 = sdiv i32 %7, %2
   %9 = mul nsw i32 %2, 50
   %10 = sdiv i32 %9, %0
   %11 = add nsw i32 %10, %8
   store i32 %11, i32* %4, align 4, !tbaa !2
   %12 = add nsw i32 %3, %1
   %13 = mul nsw i32 %12, %1
   %14 = sdiv i32 %13, %3
   %15 = mul nsw i32 %3, 50
   %16 = sdiv i32 %15, %1
   %17 = add nsw i32 %16, %14
   %18 = getelementptr inbounds i32, i32* %4, i64 1
   store i32 %17, i32* %18, align 4, !tbaa !2
   ret void
}

attributes #0 = { nofree norecurse nounwind uwtable writeonly 
"correctly-rounded-divide-sqrt-fp-math"="false" 
"disable-tail-calls"="false" "less-precise-fpmad"="false\
" "min-legal-vector-width"="0" "no-frame-pointer-elim"="false" 
"no-infs-fp-math"="false" "no-jump-tables"="false" 
"no-nans-fp-math"="false" "no-signed-zeros-fp-math"=\
"false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" 
"target-cpu"="x86-64" 
"target-features"="+cx8,+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false\
" "use-soft-float"="false" }

!llvm.module.flags = !{!0}
!llvm.ident = !{!1}

!0 = !{i32 1, !"wchar_size", i32 4}
!1 = !{!"clang version 9.0.0 (tags/RELEASE_900/final)"}
!2 = !{!3, !3, i64 0}
!3 = !{!"int", !4, i64 0}
!4 = !{!"omnipotent char", !5, i64 0}
!5 = !{!"Simple C/C++ TBAA"}
--------------------------------------------

thanks for your help.

[1] https://llvm.org/docs/Vectorizers.html#the-slp-vectorizer