Allow scalar evolution to compute iteration counts for loops with a

pointer-based condition.  This fixes PR3171.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71354 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index e65cdd218a71ce35dadd07da46b6506c547bee04..107a7c4d818ca055eec9035c5f67cf5e6c64109b 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2372,10 +2372,8 @@ ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
   
   ICmpInst *ExitCond = dyn_cast<ICmpInst>(ExitBr->getCondition());
 
-  // If it's not an integer comparison then compute it the hard way. 
-  // Note that ICmpInst deals with pointer comparisons too so we must check
-  // the type of the operand.
-  if (ExitCond == 0 || isa<PointerType>(ExitCond->getOperand(0)->getType()))
+  // If it's not an integer or pointer comparison then compute it the hard way.
+  if (ExitCond == 0)
     return ComputeBackedgeTakenCountExhaustively(L, ExitBr->getCondition(),
                                           ExitBr->getSuccessor(0) == ExitBlock);
 
@@ -2416,21 +2414,12 @@ ScalarEvolution::ComputeBackedgeTakenCount(const Loop *L) {
   if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
     if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
       if (AddRec->getLoop() == L) {
-        // Form the comparison range using the constant of the correct type so
-        // that the ConstantRange class knows to do a signed or unsigned
-        // comparison.
-        ConstantInt *CompVal = RHSC->getValue();
-        const Type *RealTy = ExitCond->getOperand(0)->getType();
-        CompVal = dyn_cast<ConstantInt>(
-          ConstantExpr::getBitCast(CompVal, RealTy));
-        if (CompVal) {
-          // Form the constant range.
-          ConstantRange CompRange(
-              ICmpInst::makeConstantRange(Cond, CompVal->getValue()));
-
-          SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange, *this);
-          if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
-        }
+        // Form the constant range.
+        ConstantRange CompRange(
+            ICmpInst::makeConstantRange(Cond, RHSC->getValue()->getValue()));
+
+        SCEVHandle Ret = AddRec->getNumIterationsInRange(CompRange, *this);
+        if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
       }
 
   switch (Cond) {

diff --git a/test/Analysis/ScalarEvolution/2009-05-09-PointerEdgeCount.ll b/test/Analysis/ScalarEvolution/2009-05-09-PointerEdgeCount.ll
new file mode 100644 (file)
index 0000000..bea46a7
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/2009-05-09-PointerEdgeCount.ll
@@ -0,0 +1,27 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution | grep {count is 2}
+; PR3171
+
+       %struct.Foo = type { i32 }
+       %struct.NonPod = type { [2 x %struct.Foo] }
+
+define void @_Z3foov() nounwind {
+entry:
+       %x = alloca %struct.NonPod, align 8             ; <%struct.NonPod*> [#uses=2]
+       %0 = getelementptr %struct.NonPod* %x, i32 0, i32 0             ; <[2 x %struct.Foo]*> [#uses=1]
+       %1 = getelementptr [2 x %struct.Foo]* %0, i32 1, i32 0          ; <%struct.Foo*> [#uses=1]
+       br label %bb1.i
+
+bb1.i:         ; preds = %bb2.i, %entry
+       %.0.i = phi %struct.Foo* [ %1, %entry ], [ %4, %bb2.i ]         ; <%struct.Foo*> [#uses=2]
+       %2 = getelementptr %struct.NonPod* %x, i32 0, i32 0, i32 0              ; <%struct.Foo*> [#uses=1]
+       %3 = icmp eq %struct.Foo* %.0.i, %2             ; <i1> [#uses=1]
+       br i1 %3, label %_ZN6NonPodD1Ev.exit, label %bb2.i
+
+bb2.i:         ; preds = %bb1.i
+       %4 = getelementptr %struct.Foo* %.0.i, i32 -1           ; <%struct.Foo*> [#uses=1]
+       br label %bb1.i
+
+_ZN6NonPodD1Ev.exit:           ; preds = %bb1.i
+       ret void
+}
+