Previously SimplifyInstruction could report that an instruction

simplified to itself (this can only happen in unreachable blocks).
Change it to return null instead.  Hopefully this will fix some
buildbot failures.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119490 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/InstructionSimplify.h b/include/llvm/Analysis/InstructionSimplify.h
index b59adc1de9b306f440ad1beb036141e997c2c42a..965e71be4110f8b3fe8db18c17f2a487dd02a8b4 100644 (file)
--- a/include/llvm/Analysis/InstructionSimplify.h
+++ b/include/llvm/Analysis/InstructionSimplify.h
@@ -75,8 +75,6 @@ namespace llvm {
 
   /// SimplifyInstruction - See if we can compute a simplified version of this
   /// instruction.  If not, this returns null.
-  /// WARNING: If called on unreachable code, an instruction may be reported
-  /// to simplify to itself.
   Value *SimplifyInstruction(Instruction *I, const TargetData *TD = 0,
                              const DominatorTree *DT = 0);
 

diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp
index c540d6fd2c03e22ad21f39f470d7025472febdfd..5ad842b38f131697881acc6c638b262a7ce2d5f9 100644 (file)
--- a/lib/Analysis/InstructionSimplify.cpp
+++ b/lib/Analysis/InstructionSimplify.cpp
@@ -756,34 +756,50 @@ Value *llvm::SimplifyCmpInst(unsigned Predicate, Value *LHS, Value *RHS,
 /// instruction.  If not, this returns null.
 Value *llvm::SimplifyInstruction(Instruction *I, const TargetData *TD,
                                  const DominatorTree *DT) {
+  Value *Result;
+
   switch (I->getOpcode()) {
   default:
-    return ConstantFoldInstruction(I, TD);
+    Result = ConstantFoldInstruction(I, TD);
+    break;
   case Instruction::Add:
-    return SimplifyAddInst(I->getOperand(0), I->getOperand(1),
-                           cast<BinaryOperator>(I)->hasNoSignedWrap(),
-                           cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
-                           TD, DT);
+    Result = SimplifyAddInst(I->getOperand(0), I->getOperand(1),
+                             cast<BinaryOperator>(I)->hasNoSignedWrap(),
+                             cast<BinaryOperator>(I)->hasNoUnsignedWrap(),
+                             TD, DT);
+    break;
   case Instruction::And:
-    return SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
   case Instruction::Or:
-    return SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
   case Instruction::ICmp:
-    return SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
-                            I->getOperand(0), I->getOperand(1), TD, DT);
+    Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
+                              I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
   case Instruction::FCmp:
-    return SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
-                            I->getOperand(0), I->getOperand(1), TD, DT);
+    Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(),
+                              I->getOperand(0), I->getOperand(1), TD, DT);
+    break;
   case Instruction::Select:
-    return SimplifySelectInst(I->getOperand(0), I->getOperand(1),
-                              I->getOperand(2), TD, DT);
+    Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
+                                I->getOperand(2), TD, DT);
+    break;
   case Instruction::GetElementPtr: {
     SmallVector<Value*, 8> Ops(I->op_begin(), I->op_end());
-    return SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
+    Result = SimplifyGEPInst(&Ops[0], Ops.size(), TD, DT);
+    break;
   }
   case Instruction::PHI:
-    return SimplifyPHINode(cast<PHINode>(I), DT);
+    Result = SimplifyPHINode(cast<PHINode>(I), DT);
+    break;
   }
+
+  /// If called on unreachable code, the above logic may report that the
+  /// instruction simplified to itself.  Make life easier for users by
+  /// detecting that case here, returning null if it occurs.
+  return Result == I ? 0 : Result;
 }
 
 /// ReplaceAndSimplifyAllUses - Perform From->replaceAllUsesWith(To) and then

diff --git a/lib/Analysis/Lint.cpp b/lib/Analysis/Lint.cpp
index 8b76b873374e2054bb5a278db3e45b6538fbfdd3..e5e7cd38576fc56f6133c507f3e3b66e989bd006 100644 (file)
--- a/lib/Analysis/Lint.cpp
+++ b/lib/Analysis/Lint.cpp
@@ -616,8 +616,7 @@ Value *Lint::findValueImpl(Value *V, bool OffsetOk,
   // As a last resort, try SimplifyInstruction or constant folding.
   if (Instruction *Inst = dyn_cast<Instruction>(V)) {
     if (Value *W = SimplifyInstruction(Inst, TD, DT))
-      if (W != Inst)
-        return findValueImpl(W, OffsetOk, Visited);
+      return findValueImpl(W, OffsetOk, Visited);
   } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
     if (Value *W = ConstantFoldConstantExpression(CE, TD))
       if (W != V)