opt: Mirror vectorization presets of clang

clang enables vectorization at optimization levels > 1 and size level < 2. opt
should behave similarily.

Loop vectorization and SLP vectorization can be disabled with the flags
-disable-(loop/slp)-vectorization.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196294 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/LoopVectorize/opt.ll

@@ -0,0 +1,28 @@
+; RUN: opt -S -O3 -force-vector-width=2 -force-vector-unroll=1 < %s | FileCheck --check-prefix=LOOPVEC %s
+; RUN: opt -S -O3 -disable-loop-vectorization -force-vector-width=2 -force-vector-unroll=1 < %s | FileCheck --check-prefix=NOLOOPVEC %s
+
+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-apple-macosx10.8.0"
+
+; Make sure we can disable vectorization in opt.
+
+; LOOPVEC:       add <2 x i32>
+; NOLOOPVEC-NOT: add <2 x i32>
+
+define i32 @vect(i32* %a) {
+entry:
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %red.05 = phi i32 [ 0, %entry ], [ %add, %for.body ]
+  %arrayidx = getelementptr inbounds i32* %a, i64 %indvars.iv
+  %0 = load i32* %arrayidx, align 4
+  %add = add nsw i32 %0, %red.05
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond = icmp eq i64 %indvars.iv.next, 255
+  br i1 %exitcond, label %for.end, label %for.body
+
+for.end:
+  ret i32 %add
+}