[llvm-commits] [llvm] r70051 - in /llvm/trunk: lib/Analysis/ScalarEvolution.cpp test/Transforms/IndVarSimplify/avoid-i0.ll

[Dan Gohman]

Author: djg
Date: Sat Apr 25 12:05:40 2009
New Revision: 70051

URL: http://llvm.org/viewvc/llvm-project?rev=70051&view=rev
Log:
Handle ands with 0 and shifts by 0 correctly. These aren't
common, but indvars shouldn't crash on them. This fixes PR4054.

Added:
    llvm/trunk/test/Transforms/IndVarSimplify/avoid-i0.ll
Modified:
    llvm/trunk/lib/Analysis/ScalarEvolution.cpp

Modified: llvm/trunk/lib/Analysis/ScalarEvolution.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ScalarEvolution.cpp?rev=70051&r1=70050&r2=70051&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ScalarEvolution.cpp (original)
+++ llvm/trunk/lib/Analysis/ScalarEvolution.cpp Sat Apr 25 12:05:40 2009
@@ -1754,6 +1754,8 @@
     // 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 @@
       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;

Added: llvm/trunk/test/Transforms/IndVarSimplify/avoid-i0.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/IndVarSimplify/avoid-i0.ll?rev=70051&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/IndVarSimplify/avoid-i0.ll (added)
+++ llvm/trunk/test/Transforms/IndVarSimplify/avoid-i0.ll Sat Apr 25 12:05:40 2009
@@ -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
+}