Check loop exit predicate properly while eliminating one iteration loop.

This patch fixes PR 2869

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@57369 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 047e6563779d3ddf442630beb46e9331540ea94d..6a2c7587f6e02f1e99b8c65206716a071533a7d9 100644 (file)
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -585,16 +585,7 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
   // only when index variable is equal to split value.
   IndVar->replaceAllUsesWith(SD.SplitValue);
 
-  // Remove Latch to Header edge.
-  BasicBlock *LatchSucc = NULL;
-  Header->removePredecessor(Latch);
-  for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
-       SI != E; ++SI) {
-    if (Header != *SI)
-      LatchSucc = *SI;
-  }
-  BR->setUnconditionalDest(LatchSucc);
-
+  Instruction *LTerminator = Latch->getTerminator();
   Instruction *Terminator = Header->getTerminator();
   Value *ExitValue = ExitCondition->getOperand(ExitValueNum);
 
@@ -606,12 +597,14 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
   //      c2 = icmp ult i32 SplitValue, ExitValue
   //      and i32 c1, c2 
   bool SignedPredicate = ExitCondition->isSignedPredicate();
+  CmpInst::Predicate C2Predicate = ExitCondition->getPredicate();
+  if (LTerminator->getOperand(0) != Header)
+    C2Predicate = CmpInst::getInversePredicate(C2Predicate);
   Instruction *C1 = new ICmpInst(SignedPredicate ? 
                                  ICmpInst::ICMP_SGE : ICmpInst::ICMP_UGE,
                                  SD.SplitValue, StartValue, "lisplit", 
                                  Terminator);
-  Instruction *C2 = new ICmpInst(SignedPredicate ? 
-                                 ICmpInst::ICMP_SLT : ICmpInst::ICMP_ULT,
+  Instruction *C2 = new ICmpInst(C2Predicate,
                                  SD.SplitValue, ExitValue, "lisplit", 
                                  Terminator);
   Instruction *NSplitCond = BinaryOperator::CreateAnd(C1, C2, "lisplit", 
@@ -619,9 +612,18 @@ bool LoopIndexSplit::processOneIterationLoop(SplitInfo &SD) {
   SD.SplitCondition->replaceAllUsesWith(NSplitCond);
   SD.SplitCondition->eraseFromParent();
 
+  // Remove Latch to Header edge.
+  BasicBlock *LatchSucc = NULL;
+  Header->removePredecessor(Latch);
+  for (succ_iterator SI = succ_begin(Latch), E = succ_end(Latch);
+       SI != E; ++SI) {
+    if (Header != *SI)
+      LatchSucc = *SI;
+  }
+  BR->setUnconditionalDest(LatchSucc);
+
   // Now, clear latch block. Remove instructions that are responsible
   // to increment induction variable. 
-  Instruction *LTerminator = Latch->getTerminator();
   for (BasicBlock::iterator LB = Latch->begin(), LE = Latch->end();
        LB != LE; ) {
     Instruction *I = LB;

diff --git a/test/Transforms/LoopIndexSplit/2008-10-10-OneIteration.ll b/test/Transforms/LoopIndexSplit/2008-10-10-OneIteration.ll
new file mode 100644 (file)
index 0000000..7c0d207
--- /dev/null
+++ b/test/Transforms/LoopIndexSplit/2008-10-10-OneIteration.ll
@@ -0,0 +1,66 @@
+; RUN: llvm-as < %s | opt -loop-index-split | llvm-dis | grep sle | count 1
+; PR 2869
+
+@w = external global [2 x [2 x i32]]           ; <[2 x [2 x i32]]*> [#uses=5]
+
+declare i32 @f() nounwind
+
+define i32 @main() noreturn nounwind {
+entry:
+       br label %bb1.i.outer
+
+bb1.i.outer:           ; preds = %bb5.i, %entry
+       %i.0.reg2mem.0.ph.i.ph = phi i32 [ 0, %entry ], [ %4, %bb5.i ]          ; <i32> [#uses=3]
+       br label %bb1.i
+
+bb1.i:         ; preds = %bb3.i, %bb1.i.outer
+       %j.0.reg2mem.0.i = phi i32 [ %2, %bb3.i ], [ 0, %bb1.i.outer ]          ; <i32> [#uses=3]
+       %0 = icmp eq i32 %i.0.reg2mem.0.ph.i.ph, %j.0.reg2mem.0.i               ; <i1> [#uses=1]
+       br i1 %0, label %bb2.i, label %bb3.i
+
+bb2.i:         ; preds = %bb1.i
+       %1 = getelementptr [2 x [2 x i32]]* @w, i32 0, i32 %i.0.reg2mem.0.ph.i.ph, i32 %j.0.reg2mem.0.i         ; <i32*> [#uses=1]
+       store i32 1, i32* %1, align 4
+       br label %bb3.i
+
+bb3.i:         ; preds = %bb2.i, %bb1.i
+       %2 = add i32 %j.0.reg2mem.0.i, 1                ; <i32> [#uses=2]
+       %3 = icmp sgt i32 %2, 1         ; <i1> [#uses=1]
+       br i1 %3, label %bb5.i, label %bb1.i
+
+bb5.i:         ; preds = %bb3.i
+       %4 = add i32 %i.0.reg2mem.0.ph.i.ph, 1          ; <i32> [#uses=2]
+       %5 = icmp sgt i32 %4, 1         ; <i1> [#uses=1]
+       br i1 %5, label %f.exit, label %bb1.i.outer
+
+f.exit:                ; preds = %bb5.i
+       %6 = load i32* getelementptr ([2 x [2 x i32]]* @w, i32 0, i32 0, i32 0), align 4                ; <i32> [#uses=1]
+       %7 = icmp eq i32 %6, 1          ; <i1> [#uses=1]
+       br i1 %7, label %bb, label %bb3
+
+bb:            ; preds = %f.exit
+       %8 = load i32* getelementptr ([2 x [2 x i32]]* @w, i32 0, i32 1, i32 1), align 4                ; <i32> [#uses=1]
+       %9 = icmp eq i32 %8, 1          ; <i1> [#uses=1]
+       br i1 %9, label %bb1, label %bb3
+
+bb1:           ; preds = %bb
+       %10 = load i32* getelementptr ([2 x [2 x i32]]* @w, i32 0, i32 1, i32 0), align 4               ; <i32> [#uses=1]
+       %11 = icmp eq i32 %10, 0                ; <i1> [#uses=1]
+       br i1 %11, label %bb2, label %bb3
+
+bb2:           ; preds = %bb1
+       %12 = load i32* getelementptr ([2 x [2 x i32]]* @w, i32 0, i32 0, i32 1), align 4               ; <i32> [#uses=1]
+       %13 = icmp eq i32 %12, 0                ; <i1> [#uses=1]
+       br i1 %13, label %bb4, label %bb3
+
+bb3:           ; preds = %bb2, %bb1, %bb, %f.exit
+       tail call void @abort() noreturn nounwind
+       unreachable
+
+bb4:           ; preds = %bb2
+       ret i32 0
+}
+
+declare void @abort() noreturn nounwind
+
+declare void @exit(i32) noreturn nounwind