Revert r309415: "[LVI] Constant-propagate a zero extension of the switch condition value through case edges"

This causes assertion failures in (a somewhat old version of) SpiderMonkey.
I have already forwarded reproduction instructions to the patch author.

llvm-svn: 309659

1 files changed, 4 insertions, 108 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index 303bb6168f8..102081e721a 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -17,7 +17,6 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/ConstantFolding.h"
-#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
 #include "llvm/IR/AssemblyAnnotationWriter.h"
@@ -149,15 +148,6 @@ public:
     return Range;
   }
 
-  Optional<APInt> asConstantInteger() const {
-    if (isConstant() && isa<ConstantInt>(Val)) {
-      return Val->getUniqueInteger();
-    } else if (isConstantRange() && Range.isSingleElement()) {
-      return *Range.getSingleElement();
-    }
-    return Optional<APInt>();
-  }
-
 private:
   void markOverdefined() {
     if (isOverdefined())
@@ -1365,42 +1355,6 @@ LVILatticeVal getValueFromCondition(Value *Val, Value *Cond, bool isTrueDest) {
   return getValueFromCondition(Val, Cond, isTrueDest, Visited);
 }
 
-// Return true if Usr has Op as an operand, otherwise false.
-static bool usesOperand(User *Usr, Value *Op) {
-  return find(Usr->operands(), Op) != Usr->op_end();
-}
-
-// Check if Val can be simplified to an integer constant when the value of one
-// of its operands Op is an integer constant OpConstVal. If so, return it as an
-// lattice value range with a single element or otherwise return an overdefined
-// lattice value.
-static LVILatticeVal constantFoldUser(Value *Val, Value *Op,
-                                      const APInt &OpConstVal,
-                                      const DataLayout &DL) {
-  Constant* OpConst = Constant::getIntegerValue(Op->getType(), OpConstVal);
-  // Check if Val can be simplified to a constant.
-  if (auto *CI = dyn_cast<CastInst>(Val)) {
-    assert(CI->getOperand(0) == Op && "Operand 0 isn't Op");
-    if (auto *C = dyn_cast_or_null<ConstantInt>(
-            SimplifyCastInst(CI->getOpcode(), OpConst,
-                             CI->getDestTy(), DL))) {
-      return LVILatticeVal::getRange(ConstantRange(C->getUniqueInteger()));
-    }
-  } else if (auto *BO = dyn_cast<BinaryOperator>(Val)) {
-    bool Op0Match = BO->getOperand(0) == Op;
-    bool Op1Match = BO->getOperand(1) == Op;
-    assert((Op0Match || Op1Match) &&
-           "Operand 0 nor Operand 1 isn't a match");
-    Value *LHS = Op0Match ? OpConst : BO->getOperand(0);
-    Value *RHS = Op1Match ? OpConst : BO->getOperand(1);
-    if (auto *C = dyn_cast_or_null<ConstantInt>(
-            SimplifyBinOp(BO->getOpcode(), LHS, RHS, DL))) {
-      return LVILatticeVal::getRange(ConstantRange(C->getUniqueInteger()));
-    }
-  }
-  return LVILatticeVal::getOverdefined();
-}
-
 /// \brief Compute the value of Val on the edge BBFrom -> BBTo. Returns false if
 /// Val is not constrained on the edge.  Result is unspecified if return value
 /// is false.
@@ -1416,11 +1370,10 @@ static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
       bool isTrueDest = BI->getSuccessor(0) == BBTo;
       assert(BI->getSuccessor(!isTrueDest) == BBTo &&
              "BBTo isn't a successor of BBFrom");
-      Value *Condition = BI->getCondition();
 
       // If V is the condition of the branch itself, then we know exactly what
       // it is.
-      if (Condition == Val) {
+      if (BI->getCondition() == Val) {
         Result = LVILatticeVal::get(ConstantInt::get(
                               Type::getInt1Ty(Val->getContext()), isTrueDest));
         return true;
@@ -1428,44 +1381,7 @@ static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
 
       // If the condition of the branch is an equality comparison, we may be
       // able to infer the value.
-      Result = getValueFromCondition(Val, Condition, isTrueDest);
-      if (!Result.isOverdefined())
-        return true;
-
-      if (User *Usr = dyn_cast<User>(Val)) {
-        assert(Result.isOverdefined() && "Result isn't overdefined");
-        if (isa<IntegerType>(Val->getType())) {
-          const DataLayout &DL = BBTo->getModule()->getDataLayout();
-          if (usesOperand(Usr, Condition)) {
-            // If Val has Condition as an operand and Val can be folded into a
-            // constant with either Condition == true or Condition == false,
-            // propagate the constant.
-            // eg.
-            //   ; %Val is true on the edge to %then.
-            //   %Val = and i1 %Condition, true.
-            //   br %Condition, label %then, label %else
-            APInt ConditionVal(1, isTrueDest ? 1 : 0);
-            Result = constantFoldUser(Val, Condition, ConditionVal, DL);
-          } else {
-            // If one of Val's operand has an inferred value, we may be able to
-            // infer the value of Val.
-            // eg.
-            //    ; %Val is 94 on the edge to %then.
-            //    %Val = add i8 %Op, 1
-            //    %Condition = icmp eq i8 %Op, 93
-            //    br i1 %Condition, label %then, label %else
-            for (unsigned i = 0; i < Usr->getNumOperands(); ++i) {
-              Value *Op = Usr->getOperand(i);
-              LVILatticeVal OpLatticeVal =
-                  getValueFromCondition(Op, Condition, isTrueDest);
-              if (Optional<APInt> OpConst = OpLatticeVal.asConstantInteger()) {
-                Result = constantFoldUser(Val, Op, OpConst.getValue(), DL);
-                break;
-              }
-            }
-          }
-        }
-      }
+      Result = getValueFromCondition(Val, BI->getCondition(), isTrueDest);
       if (!Result.isOverdefined())
         return true;
     }
@@ -1474,35 +1390,15 @@ static bool getEdgeValueLocal(Value *Val, BasicBlock *BBFrom,
   // If the edge was formed by a switch on the value, then we may know exactly
   // what it is.
   if (SwitchInst *SI = dyn_cast<SwitchInst>(BBFrom->getTerminator())) {
-    Value *Condition = SI->getCondition();
-    if (!isa<IntegerType>(Val->getType()))
+    if (SI->getCondition() != Val)
       return false;
-    bool ValUsesCondition = false;
-    if (Condition != Val) {
-      // Check if Val has Condition as an operand.
-      if (User *Usr = dyn_cast<User>(Val))
-        ValUsesCondition = usesOperand(Usr, Condition);
-      if (!ValUsesCondition)
-        return false;
-    }
-    assert((Condition == Val || ValUsesCondition) &&
-           "Condition != Val nor Val doesn't use Condition");
 
     bool DefaultCase = SI->getDefaultDest() == BBTo;
     unsigned BitWidth = Val->getType()->getIntegerBitWidth();
     ConstantRange EdgesVals(BitWidth, DefaultCase/*isFullSet*/);
 
     for (auto Case : SI->cases()) {
-      APInt CaseValue = Case.getCaseValue()->getValue();
-      ConstantRange EdgeVal(CaseValue);
-      if (ValUsesCondition) {
-        const DataLayout &DL = BBTo->getModule()->getDataLayout();
-        LVILatticeVal EdgeLatticeVal =
-            constantFoldUser(Val, Condition, CaseValue, DL);
-        if (EdgeLatticeVal.isOverdefined())
-          return false;
-        EdgeVal = EdgeLatticeVal.getConstantRange();
-      }
+      ConstantRange EdgeVal(Case.getCaseValue()->getValue());
       if (DefaultCase) {
         // It is possible that the default destination is the destination of
         // some cases. There is no need to perform difference for those cases.