[LLVMdev] loop fusion

[Andrew Clinton]

Is there a transformation in LLVM that will perform loop fusion?
http://en.wikipedia.org/wiki/Loop_fusion

I have the following program, in which I would like the 2 loops 
(iterating the same number of times) to be merged into 1, after which 
other nice optimizations such as mem2reg will apply:

; ModuleID = 'test'

define void @vector([16 x float]* nocapture %arg, [16 x float]* 
nocapture %ret) {
bb.nph12:
   %0 = alloca [16 x float], align 4               ; <[16 x float]*> 
[#uses=2]
   br label %loop

loop:                                             ; preds = %loop, 
%bb.nph12
   %indvar13 = phi i64 [ 0, %bb.nph12 ], [ %indvar.next14, %loop ] ; 
<i64> [#uses=3]
   %gep = getelementptr [16 x float]* %ret, i64 0, i64 %indvar13 ; 
<float*> [#uses=1]
   %gep1 = getelementptr [16 x float]* %0, i64 0, i64 %indvar13 ; 
<float*> [#uses=1]
   %load = load float* %gep                        ; <float> [#uses=1]
   store float %load, float* %gep1
   %indvar.next14 = add i64 %indvar13, 1           ; <i64> [#uses=2]
   %exitcond15 = icmp eq i64 %indvar.next14, 16    ; <i1> [#uses=1]
   br i1 %exitcond15, label %loop3, label %loop

loop3:                                            ; preds = %loop, %loop3
   %indvar = phi i64 [ %indvar.next, %loop3 ], [ 0, %loop ] ; <i64> 
[#uses=3]
   %gep6 = getelementptr [16 x float]* %0, i64 0, i64 %indvar ; <float*> 
[#uses=1]
   %gep8 = getelementptr [16 x float]* %arg, i64 0, i64 %indvar ; 
<float*> [#uses=1]
   %load7 = load float* %gep6                      ; <float> [#uses=1]
   store float %load7, float* %gep8
   %indvar.next = add i64 %indvar, 1               ; <i64> [#uses=2]
   %exitcond = icmp eq i64 %indvar.next, 16        ; <i1> [#uses=1]
   br i1 %exitcond, label %end4, label %loop3

end4:                                             ; preds = %loop3
   ret void
}