Handle ands with 0 and shifts by 0 correctly. These aren't

common, but indvars shouldn't crash on them. This fixes PR4054.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70051 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index 409bad9166976eebea28932de10df1ade8d78c1d..495290d8d7317b2862b1400b66f24c20f3186cdd 100644 (file)
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -1754,6 +1754,8 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
     // For an expression like x&255 that merely masks off the high bits,
     // use zext(trunc(x)) as the SCEV expression.
     if (ConstantInt *CI = dyn_cast<ConstantInt>(U->getOperand(1))) {
+      if (CI->isNullValue())
+        return getSCEV(U->getOperand(1));
       const APInt &A = CI->getValue();
       unsigned Ones = A.countTrailingOnes();
       if (APIntOps::isMask(Ones, A))
@@ -1818,10 +1820,15 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) {
       if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
         if (L->getOpcode() == Instruction::Shl &&
             L->getOperand(1) == U->getOperand(1)) {
-          uint64_t Amt = getTypeSizeInBits(U->getType()) - CI->getZExtValue();
+          unsigned BitWidth = getTypeSizeInBits(U->getType());
+          uint64_t Amt = BitWidth - CI->getZExtValue();
+          if (Amt == BitWidth)
+            return getSCEV(L->getOperand(0));       // shift by zero --> noop
+          if (Amt > BitWidth)
+            return getIntegerSCEV(0, U->getType()); // value is undefined
           return
             getSignExtendExpr(getTruncateExpr(getSCEV(L->getOperand(0)),
-                                                    IntegerType::get(Amt)),
+                                                      IntegerType::get(Amt)),
                                  U->getType());
         }
     break;

diff --git a/test/Transforms/IndVarSimplify/avoid-i0.ll b/test/Transforms/IndVarSimplify/avoid-i0.ll
new file mode 100644 (file)
index 0000000..28112e7
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/avoid-i0.ll
@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | opt -indvars
+; PR4054
+
+; Don't treat an and with 0 as a mask (trunc+zext).
+
+define i32 @int80(i8 signext %p_71) nounwind {
+entry:
+       br label %bb
+
+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
+
+bb1:           ; preds = %bb
+       ret i32 0
+
+bb4:           ; preds = %bb4, %bb
+       br i1 false, label %bb6, label %bb4
+
+bb6:           ; preds = %bb4
+       %0 = and i8 0, 0                ; <i8> [#uses=1]
+       br label %bb
+}