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https://github.com/c64scene-ar/llvm-6502.git
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160f9b9c10
Prior to this change, the loop vectorizer did not make use of the alias
analysis infrastructure. Instead, it performed memory dependence analysis using
ScalarEvolution-based linear dependence checks within equivalence classes
derived from the results of ValueTracking's GetUnderlyingObjects.
Unfortunately, this meant that:
1. The loop vectorizer had logic that essentially duplicated that in BasicAA
for aliasing based on identified objects.
2. The loop vectorizer could not partition the space of dependency checks
based on information only easily available from within AA (TBAA metadata is
currently the prime example).
This means, for example, regardless of whether -fno-strict-aliasing was
provided, the vectorizer would only vectorize this loop with a runtime
memory-overlap check:
void foo(int *a, float *b) {
for (int i = 0; i < 1600; ++i)
a[i] = b[i];
}
This is suboptimal because the TBAA metadata already provides the information
necessary to show that this check unnecessary. Of course, the vectorizer has a
limit on the number of such checks it will insert, so in practice, ignoring
TBAA means not vectorizing more-complicated loops that we should.
This change causes the vectorizer to use an AliasSetTracker to keep track of
the pointers in the loop. The resulting alias sets are then used to partition
the space of dependency checks, and potential runtime checks; this results in
more-efficient vectorizations.
When pointer locations are added to the AliasSetTracker, two things are done:
1. The location size is set to UnknownSize (otherwise you'd not catch
inter-iteration dependencies)
2. For instructions in blocks that would need to be predicated, TBAA is
removed (because the metadata might have a control dependency on the condition
being speculated).
For non-predicated blocks, you can leave the TBAA metadata. This is safe
because you can't have an iteration dependency on the TBAA metadata (if you
did, and you unrolled sufficiently, you'd end up with the same pointer value
used by two accesses that TBAA says should not alias, and that would yield
undefined behavior).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213486 91177308-0d34-0410-b5e6-96231b3b80d8
196 lines
7.3 KiB
LLVM
196 lines
7.3 KiB
LLVM
; RUN: opt < %s -basicaa -loop-vectorize -force-vector-unroll=1 -force-vector-width=4 -loop-vectorize-with-block-frequency -dce -instcombine -S | FileCheck %s
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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"
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target triple = "x86_64-apple-macosx10.8.0"
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@b = common global [2048 x i32] zeroinitializer, align 16
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@c = common global [2048 x i32] zeroinitializer, align 16
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@a = common global [2048 x i32] zeroinitializer, align 16
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@G = common global [32 x [1024 x i32]] zeroinitializer, align 16
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@ub = common global [1024 x i32] zeroinitializer, align 16
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@uc = common global [1024 x i32] zeroinitializer, align 16
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@d = common global [2048 x i32] zeroinitializer, align 16
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@fa = common global [1024 x float] zeroinitializer, align 16
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@fb = common global [1024 x float] zeroinitializer, align 16
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@ic = common global [1024 x i32] zeroinitializer, align 16
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@da = common global [1024 x float] zeroinitializer, align 16
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@db = common global [1024 x float] zeroinitializer, align 16
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@dc = common global [1024 x float] zeroinitializer, align 16
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@dd = common global [1024 x float] zeroinitializer, align 16
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@dj = common global [1024 x i32] zeroinitializer, align 16
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; We can optimize this test without a tail.
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;CHECK-LABEL: @example1(
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;CHECK: load <4 x i32>
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;CHECK: add nsw <4 x i32>
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;CHECK: store <4 x i32>
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;CHECK: ret void
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define void @example1() optsize {
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br label %1
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; <label>:1 ; preds = %1, %0
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%indvars.iv = phi i64 [ 0, %0 ], [ %indvars.iv.next, %1 ]
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%2 = getelementptr inbounds [2048 x i32]* @b, i64 0, i64 %indvars.iv
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%3 = load i32* %2, align 4
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%4 = getelementptr inbounds [2048 x i32]* @c, i64 0, i64 %indvars.iv
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%5 = load i32* %4, align 4
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%6 = add nsw i32 %5, %3
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%7 = getelementptr inbounds [2048 x i32]* @a, i64 0, i64 %indvars.iv
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store i32 %6, i32* %7, align 4
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%indvars.iv.next = add i64 %indvars.iv, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32
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%exitcond = icmp eq i32 %lftr.wideiv, 256
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br i1 %exitcond, label %8, label %1
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; <label>:8 ; preds = %1
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ret void
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}
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; Can't vectorize in 'optsize' mode because we need a tail.
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;CHECK-LABEL: @example2(
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;CHECK-NOT: store <4 x i32>
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;CHECK: ret void
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define void @example2(i32 %n, i32 %x) optsize {
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%1 = icmp sgt i32 %n, 0
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br i1 %1, label %.lr.ph5, label %.preheader
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..preheader_crit_edge: ; preds = %.lr.ph5
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%phitmp = sext i32 %n to i64
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br label %.preheader
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.preheader: ; preds = %..preheader_crit_edge, %0
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%i.0.lcssa = phi i64 [ %phitmp, %..preheader_crit_edge ], [ 0, %0 ]
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%2 = icmp eq i32 %n, 0
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br i1 %2, label %._crit_edge, label %.lr.ph
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.lr.ph5: ; preds = %0, %.lr.ph5
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%indvars.iv6 = phi i64 [ %indvars.iv.next7, %.lr.ph5 ], [ 0, %0 ]
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%3 = getelementptr inbounds [2048 x i32]* @b, i64 0, i64 %indvars.iv6
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store i32 %x, i32* %3, align 4
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%indvars.iv.next7 = add i64 %indvars.iv6, 1
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%lftr.wideiv = trunc i64 %indvars.iv.next7 to i32
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%exitcond = icmp eq i32 %lftr.wideiv, %n
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br i1 %exitcond, label %..preheader_crit_edge, label %.lr.ph5
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.lr.ph: ; preds = %.preheader, %.lr.ph
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%indvars.iv = phi i64 [ %indvars.iv.next, %.lr.ph ], [ %i.0.lcssa, %.preheader ]
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%.02 = phi i32 [ %4, %.lr.ph ], [ %n, %.preheader ]
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%4 = add nsw i32 %.02, -1
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%5 = getelementptr inbounds [2048 x i32]* @b, i64 0, i64 %indvars.iv
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%6 = load i32* %5, align 4
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%7 = getelementptr inbounds [2048 x i32]* @c, i64 0, i64 %indvars.iv
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%8 = load i32* %7, align 4
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%9 = and i32 %8, %6
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%10 = getelementptr inbounds [2048 x i32]* @a, i64 0, i64 %indvars.iv
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store i32 %9, i32* %10, align 4
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%indvars.iv.next = add i64 %indvars.iv, 1
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%11 = icmp eq i32 %4, 0
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br i1 %11, label %._crit_edge, label %.lr.ph
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._crit_edge: ; preds = %.lr.ph, %.preheader
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ret void
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}
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; N is unknown, we need a tail. Can't vectorize.
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;CHECK-LABEL: @example3(
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;CHECK-NOT: <4 x i32>
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;CHECK: ret void
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define void @example3(i32 %n, i32* noalias nocapture %p, i32* noalias nocapture %q) optsize {
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%1 = icmp eq i32 %n, 0
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br i1 %1, label %._crit_edge, label %.lr.ph
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.lr.ph: ; preds = %0, %.lr.ph
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%.05 = phi i32 [ %2, %.lr.ph ], [ %n, %0 ]
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%.014 = phi i32* [ %5, %.lr.ph ], [ %p, %0 ]
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%.023 = phi i32* [ %3, %.lr.ph ], [ %q, %0 ]
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%2 = add nsw i32 %.05, -1
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%3 = getelementptr inbounds i32* %.023, i64 1
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%4 = load i32* %.023, align 16
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%5 = getelementptr inbounds i32* %.014, i64 1
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store i32 %4, i32* %.014, align 16
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%6 = icmp eq i32 %2, 0
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br i1 %6, label %._crit_edge, label %.lr.ph
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._crit_edge: ; preds = %.lr.ph, %0
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ret void
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}
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; N is unknown, we need a tail. Can't vectorize because the loop is cold.
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;CHECK-LABEL: @example4(
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;CHECK-NOT: <4 x i32>
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;CHECK: ret void
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define void @example4(i32 %n, i32* noalias nocapture %p, i32* noalias nocapture %q) {
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%1 = icmp eq i32 %n, 0
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br i1 %1, label %._crit_edge, label %.lr.ph, !prof !0
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.lr.ph: ; preds = %0, %.lr.ph
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%.05 = phi i32 [ %2, %.lr.ph ], [ %n, %0 ]
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%.014 = phi i32* [ %5, %.lr.ph ], [ %p, %0 ]
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%.023 = phi i32* [ %3, %.lr.ph ], [ %q, %0 ]
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%2 = add nsw i32 %.05, -1
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%3 = getelementptr inbounds i32* %.023, i64 1
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%4 = load i32* %.023, align 16
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%5 = getelementptr inbounds i32* %.014, i64 1
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store i32 %4, i32* %.014, align 16
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%6 = icmp eq i32 %2, 0
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br i1 %6, label %._crit_edge, label %.lr.ph
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._crit_edge: ; preds = %.lr.ph, %0
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ret void
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}
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!0 = metadata !{metadata !"branch_weights", i32 64, i32 4}
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; We can't vectorize this one because we need a runtime ptr check.
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;CHECK-LABEL: @example23(
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;CHECK-NOT: <4 x i32>
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;CHECK: ret void
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define void @example23(i16* nocapture %src, i32* nocapture %dst) optsize {
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br label %1
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; <label>:1 ; preds = %1, %0
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%.04 = phi i16* [ %src, %0 ], [ %2, %1 ]
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%.013 = phi i32* [ %dst, %0 ], [ %6, %1 ]
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%i.02 = phi i32 [ 0, %0 ], [ %7, %1 ]
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%2 = getelementptr inbounds i16* %.04, i64 1
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%3 = load i16* %.04, align 2
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%4 = zext i16 %3 to i32
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%5 = shl nuw nsw i32 %4, 7
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%6 = getelementptr inbounds i32* %.013, i64 1
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store i32 %5, i32* %.013, align 4
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%7 = add nsw i32 %i.02, 1
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%exitcond = icmp eq i32 %7, 256
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br i1 %exitcond, label %8, label %1
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; <label>:8 ; preds = %1
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ret void
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}
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; We CAN vectorize this example because the pointers are marked as noalias.
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;CHECK-LABEL: @example23b(
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;CHECK: <4 x i32>
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;CHECK: ret void
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define void @example23b(i16* noalias nocapture %src, i32* noalias nocapture %dst) optsize {
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br label %1
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; <label>:1 ; preds = %1, %0
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%.04 = phi i16* [ %src, %0 ], [ %2, %1 ]
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%.013 = phi i32* [ %dst, %0 ], [ %6, %1 ]
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%i.02 = phi i32 [ 0, %0 ], [ %7, %1 ]
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%2 = getelementptr inbounds i16* %.04, i64 1
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%3 = load i16* %.04, align 2
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%4 = zext i16 %3 to i32
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%5 = shl nuw nsw i32 %4, 7
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%6 = getelementptr inbounds i32* %.013, i64 1
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store i32 %5, i32* %.013, align 4
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%7 = add nsw i32 %i.02, 1
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%exitcond = icmp eq i32 %7, 256
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br i1 %exitcond, label %8, label %1
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; <label>:8 ; preds = %1
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ret void
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}
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