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Teach ScalarEvolution how to compute a tripcount for a loop with
true or false as its exit condition. These are usually eliminated by SimplifyCFG, but the may be left around during a pass which wishes to preserve the CFG. llvm-svn: 96683
This commit is contained in:
Dan Gohman
parent
c03fbf812d
commit
9268d67079
@ -3703,6 +3703,19 @@ ScalarEvolution::ComputeBackedgeTakenCountFromExitCond(const Loop *L,
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if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
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return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
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// Check for a constant condition. These are normally stripped out by
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// SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
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// preserve the CFG and is temporarily leaving constant conditions
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// in place.
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if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
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if (L->contains(FBB) == !CI->getZExtValue())
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// The backedge is always taken.
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return getCouldNotCompute();
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else
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// The backedge is never taken.
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return getIntegerSCEV(0, CI->getType());
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}
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// If it's not an integer or pointer comparison then compute it the hard way.
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return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
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}
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76
test/Analysis/ScalarEvolution/trip-count10.ll
Normal file
76
test/Analysis/ScalarEvolution/trip-count10.ll
Normal file
@ -0,0 +1,76 @@
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; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
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; Trip counts with trivial exit conditions.
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; CHECK: Determining loop execution counts for: @a
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; CHECK: Loop %loop: Unpredictable backedge-taken count.
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; CHECK: Loop %loop: Unpredictable max backedge-taken count.
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; CHECK: Determining loop execution counts for: @b
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; CHECK: Loop %loop: backedge-taken count is false
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; CHECK: Loop %loop: max backedge-taken count is false
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; CHECK: Determining loop execution counts for: @c
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; CHECK: Loop %loop: backedge-taken count is false
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; CHECK: Loop %loop: max backedge-taken count is false
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; CHECK: Determining loop execution counts for: @d
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; CHECK: Loop %loop: Unpredictable backedge-taken count.
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; CHECK: Loop %loop: Unpredictable max backedge-taken count.
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define void @a(i64 %n) nounwind {
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entry:
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%t0 = icmp sgt i64 %n, 0
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br i1 %t0, label %loop, label %return
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loop:
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%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
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%i.next = add nsw i64 %i, 1
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%exitcond = icmp eq i64 %i.next, %n
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br i1 false, label %return, label %loop
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return:
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ret void
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}
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define void @b(i64 %n) nounwind {
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entry:
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%t0 = icmp sgt i64 %n, 0
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br i1 %t0, label %loop, label %return
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loop:
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%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
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%i.next = add nsw i64 %i, 1
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%exitcond = icmp eq i64 %i.next, %n
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br i1 true, label %return, label %loop
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return:
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ret void
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}
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define void @c(i64 %n) nounwind {
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entry:
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%t0 = icmp sgt i64 %n, 0
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br i1 %t0, label %loop, label %return
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loop:
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%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
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%i.next = add nsw i64 %i, 1
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%exitcond = icmp eq i64 %i.next, %n
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br i1 false, label %loop, label %return
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return:
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ret void
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}
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define void @d(i64 %n) nounwind {
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entry:
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%t0 = icmp sgt i64 %n, 0
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br i1 %t0, label %loop, label %return
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loop:
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%i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
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%i.next = add nsw i64 %i, 1
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%exitcond = icmp eq i64 %i.next, %n
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br i1 true, label %loop, label %return
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return:
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ret void
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}
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@ -7,7 +7,7 @@ define i32 @test() {
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LoopHead: ; preds = %LoopHead, %0, %0
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%A = phi i32 [ 7, %0 ], [ 7, %0 ], [ %B, %LoopHead ] ; <i32> [#uses=1]
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%B = add i32 %A, 1 ; <i32> [#uses=2]
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br i1 false, label %LoopHead, label %Out
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br i1 undef, label %LoopHead, label %Out
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Out: ; preds = %LoopHead
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ret i32 %B
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@ -10,7 +10,7 @@ no_exit: ; preds = %no_exit, %entry
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%k.0.pn = phi i32 [ %inc.4, %no_exit ], [ 1, %entry ] ; <i32> [#uses=1]
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%inc.3 = add i32 %j.0.pn, 1 ; <i32> [#uses=1]
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%inc.4 = add i32 %k.0.pn, 1 ; <i32> [#uses=1]
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br i1 false, label %no_exit, label %loopexit
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br i1 undef, label %no_exit, label %loopexit
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loopexit: ; preds = %no_exit, %entry
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ret void
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@ -8,7 +8,7 @@ cond_continue.3: ; preds = %entry
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loopexit.14: ; preds = %entry
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%tmp.738 = sub i32 0, 0 ; <i32> [#uses=1]
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br i1 false, label %no_exit.15.preheader, label %loopexit.15
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br i1 undef, label %no_exit.15.preheader, label %loopexit.15
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no_exit.15.preheader: ; preds = %loopexit.14
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br label %no_exit.15
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@ -16,7 +16,7 @@ no_exit.15.preheader: ; preds = %loopexit.14
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no_exit.15: ; preds = %no_exit.15, %no_exit.15.preheader
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%highC.0 = phi i32 [ %tmp.738, %no_exit.15.preheader ], [ %dec.0, %no_exit.15 ] ; <i32> [#uses=1]
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%dec.0 = add i32 %highC.0, -1 ; <i32> [#uses=1]
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br i1 false, label %no_exit.15, label %loopexit.15
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br i1 undef, label %no_exit.15, label %loopexit.15
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loopexit.15: ; preds = %no_exit.15, %loopexit.14
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ret void
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@ -9,7 +9,7 @@ entry:
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no_exit.0: ; preds = %no_exit.0, %entry
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%p.0.0 = phi i32* [ getelementptr ([29 x [29 x [2 x i32]]]* @fixtab, i32 0, i32 0, i32 0, i32 0), %entry ], [ %inc.0, %no_exit.0 ] ; <i32*> [#uses=1]
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%inc.0 = getelementptr i32* %p.0.0, i32 1 ; <i32*> [#uses=1]
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br i1 false, label %no_exit.0, label %no_exit.1
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br i1 undef, label %no_exit.0, label %no_exit.1
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no_exit.1: ; preds = %no_exit.0
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ret void
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@ -20,7 +20,7 @@ cond_next182.i: ; preds = %cond_next182.i, %cond_true52
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%tmp194.i53 = bitcast i32 %decay.i.0 to float ; <float> [#uses=1]
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%tmp195.i = fsub float %tmp194.i53, 8.000000e+00 ; <float> [#uses=1]
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%tmp195.i.upgrd.1 = bitcast float %tmp195.i to i32 ; <i32> [#uses=1]
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br i1 false, label %cond_next182.i, label %bb418.i.preheader
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br i1 undef, label %cond_next182.i, label %bb418.i.preheader
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bb418.i.preheader: ; preds = %cond_next182.i
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ret void
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@ -12,7 +12,7 @@ bb.nph1.preheader: ; preds = %4
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br label %bb.nph1
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bb.nph1: ; preds = %.outer, %bb.nph1.preheader
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br i1 false, label %bb.nph3.preheader, label %.outer
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br i1 undef, label %bb.nph3.preheader, label %.outer
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bb.nph3.preheader: ; preds = %bb.nph1
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br label %bb.nph3
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@ -31,7 +31,7 @@ bb.nph3: ; preds = %bb.nph3, %bb.nph3.preheader
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br label %.outer
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.outer: ; preds = %.outer.loopexit, %bb.nph1
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br i1 false, label %bb.nph1, label %.outer._crit_edge.loopexit
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br i1 undef, label %bb.nph1, label %.outer._crit_edge.loopexit
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.outer._crit_edge.loopexit: ; preds = %.outer
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br label %.outer._crit_edge
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@ -10,13 +10,13 @@ entry:
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bb: ; preds = %bb6, %entry
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%p_71_addr.0 = phi i8 [ %p_71, %entry ], [ %0, %bb6 ] ; <i8> [#uses=0]
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br i1 false, label %bb4, label %bb1
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br i1 undef, label %bb4, label %bb1
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bb1: ; preds = %bb
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ret i32 0
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bb4: ; preds = %bb4, %bb
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br i1 false, label %bb6, label %bb4
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br i1 undef, label %bb6, label %bb4
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bb6: ; preds = %bb4
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%0 = and i8 0, 0 ; <i8> [#uses=1]
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@ -16,7 +16,7 @@ bb2: ; preds = %bb2, %entry
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%str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; <i8*> [#uses=1]
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%1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; <i8*> [#uses=2]
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%2 = icmp ult i8* %1, %inLastBytePtr ; <i1> [#uses=0]
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br i1 false, label %bb2, label %return
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br i1 undef, label %bb2, label %return
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return: ; preds = %bb2
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ret void
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@ -32,7 +32,7 @@ bb2: ; preds = %bb2, %entry
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%str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; <i8*> [#uses=1]
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%1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; <i8*> [#uses=2]
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%2 = icmp slt i8* %1, %inLastBytePtr ; <i1> [#uses=0]
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br i1 false, label %bb2, label %return
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br i1 undef, label %bb2, label %return
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return: ; preds = %bb2
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ret void
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