If loop induction variable's start value is less then its exit value then do not...

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53265 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 45d4900ca86f8c3657ed0718abdcab9bac916849..135ce33ee6f4918c9487ee12ede6f1f7f44047fb 100644 (file)
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -384,6 +384,19 @@ void LoopIndexSplit::findLoopConditionals() {
     BasicBlock *Preheader = L->getLoopPreheader();
     StartValue = IndVar->getIncomingValueForBlock(Preheader);
   }
+
+  // If start value is more then exit value where induction variable
+  // increments by 1 then we are potentially dealing with an infinite loop.
+  // Do not index split this loop.
+  if (ExitCondition) {
+    ConstantInt *SV = dyn_cast<ConstantInt>(StartValue);
+    ConstantInt *EV = 
+      dyn_cast<ConstantInt>(ExitCondition->getOperand(ExitValueNum));
+    if (SV && EV && SV->getSExtValue() > EV->getSExtValue())
+      ExitCondition = NULL;
+    else if (EV && EV->isZero())
+      ExitCondition = NULL;
+  }
 }
 
 /// Find condition inside a loop that is suitable candidate for index split.

diff --git a/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll b/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
index 8aa2e52b3fe9142daccbb0277ae7b2de4d238cc0..c4678b47ac40e635c39db40c129da7830f83f7bc 100644 (file)
--- a/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
+++ b/test/Transforms/LoopIndexSplit/2008-05-19-IndVar.ll
@@ -24,7 +24,7 @@ bb4.i:                ; preds = %bb.i
        br label %bb6.i
 bb6.i:         ; preds = %bb4.i, %bb.i
        %tmp8.i = add i16 %g_2.tmp.0.i, 1               ; <i16> [#uses=3]
-       %tmp11.i = icmp sgt i16 %tmp8.i, 0              ; <i1> [#uses=1]
+       %tmp11.i = icmp sgt i16 %tmp8.i, 42             ; <i1> [#uses=1]
        br i1 %tmp11.i, label %bb.i, label %return.loopexit.i
 return.loopexit.i:             ; preds = %bb6.i
        %tmp8.i.lcssa = phi i16 [ %tmp8.i, %bb6.i ]             ; <i16> [#uses=1]

diff --git a/test/Transforms/LoopIndexSplit/2008-07-08-MisCompilation.ll b/test/Transforms/LoopIndexSplit/2008-07-08-MisCompilation.ll
new file mode 100644 (file)
index 0000000..7592511
--- /dev/null
+++ b/test/Transforms/LoopIndexSplit/2008-07-08-MisCompilation.ll
@@ -0,0 +1,25 @@
+; RUN: llvm-as < %s | opt -loop-index-split -stats -disable-output | not grep "1 loop-index-split"
+; PR 2487
+@g_6 = external global i32             ; <i32*> [#uses=1]
+
+define void @func_1() nounwind  {
+entry:
+       br label %bb
+
+bb:            ; preds = %bb4, %entry
+       %l_3.0 = phi i8 [ 0, %entry ], [ %tmp6, %bb4 ]          ; <i8> [#uses=2]
+       %tmp1 = icmp eq i8 %l_3.0, 0            ; <i1> [#uses=1]
+       br i1 %tmp1, label %bb3, label %bb4
+
+bb3:           ; preds = %bb
+       store i32 1, i32* @g_6, align 4
+       br label %bb4
+
+bb4:           ; preds = %bb3, %bb
+       %tmp6 = add i8 %l_3.0, 1                ; <i8> [#uses=2]
+       %tmp9 = icmp sgt i8 %tmp6, -1           ; <i1> [#uses=1]
+       br i1 %tmp9, label %bb, label %return
+
+return:                ; preds = %bb4
+       ret void
+}