This fork works with llvm-general-3.4.6.0.

dotp.s

; ModuleID = 'dotp.c'
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
target triple = "x86_64-unknown-linux-gnu"

; Function Attrs: nounwind readonly uwtable
define float @dotp(float* nocapture %a, float* nocapture %b, i32 %count) #0 {
  %1 = icmp sgt i32 %count, 0
  br i1 %1, label %.lr.ph, label %._crit_edge

.lr.ph:                                           ; preds = %0, %.lr.ph
  %indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ 0, %0 ]
  %res.01 = phi float [ %7, %.lr.ph ], [ 0.000000e+00, %0 ]
  %2 = getelementptr inbounds float* %a, i64 %indvars.iv
  %3 = load float* %2, align 4, !tbaa !0
  %4 = getelementptr inbounds float* %b, i64 %indvars.iv
  %5 = load float* %4, align 4, !tbaa !0
  %6 = fmul fast float %3, %5
  %7 = fadd fast float %res.01, %6
  %indvars.iv.next = add i64 %indvars.iv, 1
  %lftr.wideiv = trunc i64 %indvars.iv.next to i32
  %exitcond = icmp eq i32 %lftr.wideiv, %count
  br i1 %exitcond, label %._crit_edge, label %.lr.ph

._crit_edge:                                      ; preds = %.lr.ph, %0
  %res.0.lcssa = phi float [ 0.000000e+00, %0 ], [ %7, %.lr.ph ]
  ret float %res.0.lcssa
}

attributes #0 = { nounwind readonly uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-frame-pointer-elim-non-leaf"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "unsafe-fp-math"="false" "use-soft-float"="false" }

!0 = metadata !{metadata !"float", metadata !1}
!1 = metadata !{metadata !"omnipotent char", metadata !2}
!2 = metadata !{metadata !"Simple C/C++ TBAA"}

test.hs

import LLVM.General.Context
import LLVM.General.Module
import Control.Monad.Except
import LLVM.General.PassManager
import LLVM.General.Transforms

main :: IO ()
main = do
  mt <- readFile "dotp.s"
  _ <- withContext $ \cx -> runExceptT $ withModuleFromLLVMAssembly cx mt $ \modu -> do
    let ps = defaultCuratedPassSetSpec {optLevel=Just 3}
        ps1 = defaultPassSetSpec {transforms=[LoopVectorize True]}
    b1 <- withPassManager ps $ \pm -> runPassManager pm modu
    b2 <- withPassManager ps1 $ \pm -> runPassManager pm modu
    print [b1,b2]
    moduleLLVMAssembly modu >>= putStrLn
    print defaultVectorizeBasicBlocks
  return ()