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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96683 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index c2284a8..a0700ba 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -3703,6 +3703,19 @@
if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond))
return ComputeBackedgeTakenCountFromExitCondICmp(L, ExitCondICmp, TBB, FBB);
+ // Check for a constant condition. These are normally stripped out by
+ // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
+ // preserve the CFG and is temporarily leaving constant conditions
+ // in place.
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
+ if (L->contains(FBB) == !CI->getZExtValue())
+ // The backedge is always taken.
+ return getCouldNotCompute();
+ else
+ // The backedge is never taken.
+ return getIntegerSCEV(0, CI->getType());
+ }
+
// If it's not an integer or pointer comparison then compute it the hard way.
return ComputeBackedgeTakenCountExhaustively(L, ExitCond, !L->contains(TBB));
}
diff --git a/test/Analysis/ScalarEvolution/trip-count10.ll b/test/Analysis/ScalarEvolution/trip-count10.ll
new file mode 100644
index 0000000..0a992f9
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/trip-count10.ll
@@ -0,0 +1,76 @@
+; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
+
+; Trip counts with trivial exit conditions.
+
+; CHECK: Determining loop execution counts for: @a
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
+
+; CHECK: Determining loop execution counts for: @b
+; CHECK: Loop %loop: backedge-taken count is false
+; CHECK: Loop %loop: max backedge-taken count is false
+
+; CHECK: Determining loop execution counts for: @c
+; CHECK: Loop %loop: backedge-taken count is false
+; CHECK: Loop %loop: max backedge-taken count is false
+
+; CHECK: Determining loop execution counts for: @d
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
+
+define void @a(i64 %n) nounwind {
+entry:
+ %t0 = icmp sgt i64 %n, 0
+ br i1 %t0, label %loop, label %return
+
+loop:
+ %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+ %i.next = add nsw i64 %i, 1
+ %exitcond = icmp eq i64 %i.next, %n
+ br i1 false, label %return, label %loop
+
+return:
+ ret void
+}
+define void @b(i64 %n) nounwind {
+entry:
+ %t0 = icmp sgt i64 %n, 0
+ br i1 %t0, label %loop, label %return
+
+loop:
+ %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+ %i.next = add nsw i64 %i, 1
+ %exitcond = icmp eq i64 %i.next, %n
+ br i1 true, label %return, label %loop
+
+return:
+ ret void
+}
+define void @c(i64 %n) nounwind {
+entry:
+ %t0 = icmp sgt i64 %n, 0
+ br i1 %t0, label %loop, label %return
+
+loop:
+ %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+ %i.next = add nsw i64 %i, 1
+ %exitcond = icmp eq i64 %i.next, %n
+ br i1 false, label %loop, label %return
+
+return:
+ ret void
+}
+define void @d(i64 %n) nounwind {
+entry:
+ %t0 = icmp sgt i64 %n, 0
+ br i1 %t0, label %loop, label %return
+
+loop:
+ %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+ %i.next = add nsw i64 %i, 1
+ %exitcond = icmp eq i64 %i.next, %n
+ br i1 true, label %loop, label %return
+
+return:
+ ret void
+}
diff --git a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
index 36d5006..30d9ea6 100644
--- a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
+++ b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
@@ -7,7 +7,7 @@
LoopHead: ; preds = %LoopHead, %0, %0
%A = phi i32 [ 7, %0 ], [ 7, %0 ], [ %B, %LoopHead ] ; <i32> [#uses=1]
%B = add i32 %A, 1 ; <i32> [#uses=2]
- br i1 false, label %LoopHead, label %Out
+ br i1 undef, label %LoopHead, label %Out
Out: ; preds = %LoopHead
ret i32 %B
diff --git a/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll b/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll
index 70ea11e..7536331 100644
--- a/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll
+++ b/test/Transforms/IndVarSimplify/2003-12-10-RemoveInstrCrash.ll
@@ -10,7 +10,7 @@
%k.0.pn = phi i32 [ %inc.4, %no_exit ], [ 1, %entry ] ; <i32> [#uses=1]
%inc.3 = add i32 %j.0.pn, 1 ; <i32> [#uses=1]
%inc.4 = add i32 %k.0.pn, 1 ; <i32> [#uses=1]
- br i1 false, label %no_exit, label %loopexit
+ br i1 undef, label %no_exit, label %loopexit
loopexit: ; preds = %no_exit, %entry
ret void
diff --git a/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll b/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll
index 5aa2d90..662828c 100644
--- a/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll
+++ b/test/Transforms/IndVarSimplify/2003-12-15-Crash.ll
@@ -8,7 +8,7 @@
loopexit.14: ; preds = %entry
%tmp.738 = sub i32 0, 0 ; <i32> [#uses=1]
- br i1 false, label %no_exit.15.preheader, label %loopexit.15
+ br i1 undef, label %no_exit.15.preheader, label %loopexit.15
no_exit.15.preheader: ; preds = %loopexit.14
br label %no_exit.15
@@ -16,7 +16,7 @@
no_exit.15: ; preds = %no_exit.15, %no_exit.15.preheader
%highC.0 = phi i32 [ %tmp.738, %no_exit.15.preheader ], [ %dec.0, %no_exit.15 ] ; <i32> [#uses=1]
%dec.0 = add i32 %highC.0, -1 ; <i32> [#uses=1]
- br i1 false, label %no_exit.15, label %loopexit.15
+ br i1 undef, label %no_exit.15, label %loopexit.15
loopexit.15: ; preds = %no_exit.15, %loopexit.14
ret void
diff --git a/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll b/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll
index f9a3fe6..7202c7a 100644
--- a/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll
+++ b/test/Transforms/IndVarSimplify/2005-11-18-Crash.ll
@@ -9,7 +9,7 @@
no_exit.0: ; preds = %no_exit.0, %entry
%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]
%inc.0 = getelementptr i32* %p.0.0, i32 1 ; <i32*> [#uses=1]
- br i1 false, label %no_exit.0, label %no_exit.1
+ br i1 undef, label %no_exit.0, label %no_exit.1
no_exit.1: ; preds = %no_exit.0
ret void
diff --git a/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll b/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll
index 79ac1f0..80c9ebf 100644
--- a/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll
+++ b/test/Transforms/IndVarSimplify/2006-12-10-BitCast.ll
@@ -20,7 +20,7 @@
%tmp194.i53 = bitcast i32 %decay.i.0 to float ; <float> [#uses=1]
%tmp195.i = fsub float %tmp194.i53, 8.000000e+00 ; <float> [#uses=1]
%tmp195.i.upgrd.1 = bitcast float %tmp195.i to i32 ; <i32> [#uses=1]
- br i1 false, label %cond_next182.i, label %bb418.i.preheader
+ br i1 undef, label %cond_next182.i, label %bb418.i.preheader
bb418.i.preheader: ; preds = %cond_next182.i
ret void
diff --git a/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll b/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll
index 9ad8691..d73eee8 100644
--- a/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll
+++ b/test/Transforms/IndVarSimplify/2009-05-24-useafterfree.ll
@@ -12,7 +12,7 @@
br label %bb.nph1
bb.nph1: ; preds = %.outer, %bb.nph1.preheader
- br i1 false, label %bb.nph3.preheader, label %.outer
+ br i1 undef, label %bb.nph3.preheader, label %.outer
bb.nph3.preheader: ; preds = %bb.nph1
br label %bb.nph3
@@ -31,7 +31,7 @@
br label %.outer
.outer: ; preds = %.outer.loopexit, %bb.nph1
- br i1 false, label %bb.nph1, label %.outer._crit_edge.loopexit
+ br i1 undef, label %bb.nph1, label %.outer._crit_edge.loopexit
.outer._crit_edge.loopexit: ; preds = %.outer
br label %.outer._crit_edge
diff --git a/test/Transforms/IndVarSimplify/avoid-i0.ll b/test/Transforms/IndVarSimplify/avoid-i0.ll
index d110a8a..59661fa 100644
--- a/test/Transforms/IndVarSimplify/avoid-i0.ll
+++ b/test/Transforms/IndVarSimplify/avoid-i0.ll
@@ -10,13 +10,13 @@
bb: ; preds = %bb6, %entry
%p_71_addr.0 = phi i8 [ %p_71, %entry ], [ %0, %bb6 ] ; <i8> [#uses=0]
- br i1 false, label %bb4, label %bb1
+ br i1 undef, label %bb4, label %bb1
bb1: ; preds = %bb
ret i32 0
bb4: ; preds = %bb4, %bb
- br i1 false, label %bb6, label %bb4
+ br i1 undef, label %bb6, label %bb4
bb6: ; preds = %bb4
%0 = and i8 0, 0 ; <i8> [#uses=1]
diff --git a/test/Transforms/IndVarSimplify/max-pointer.ll b/test/Transforms/IndVarSimplify/max-pointer.ll
index 71bc720..f18f968 100644
--- a/test/Transforms/IndVarSimplify/max-pointer.ll
+++ b/test/Transforms/IndVarSimplify/max-pointer.ll
@@ -16,7 +16,7 @@
%str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; <i8*> [#uses=1]
%1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; <i8*> [#uses=2]
%2 = icmp ult i8* %1, %inLastBytePtr ; <i1> [#uses=0]
- br i1 false, label %bb2, label %return
+ br i1 undef, label %bb2, label %return
return: ; preds = %bb2
ret void
@@ -32,7 +32,7 @@
%str2Ptr_addr.1 = phi i8* [ %str2Ptr_addr.0, %entry ], [ %1, %bb2 ] ; <i8*> [#uses=1]
%1 = getelementptr i8* %str2Ptr_addr.1, i64 1 ; <i8*> [#uses=2]
%2 = icmp slt i8* %1, %inLastBytePtr ; <i1> [#uses=0]
- br i1 false, label %bb2, label %return
+ br i1 undef, label %bb2, label %return
return: ; preds = %bb2
ret void