Backport 4878aa36d4a [ValueLattice] Add new state for undef constants.

Summary:
NOTE: I mostly put it on Phabricator to make it easy for other people to fetch & check if that fixes a bug.

This patch backports 4878aa36d4a and required earlier patches onto
the release/10.x branch.

It includes the following patches:

aa5ebfdf205de6d599c1fed3161da3b63b6f0bef [ValueLattice] Make mark* functions public, return if value changed.

c1943b42c5b7feff5d0e0c1358d02889e2be165f [ValueLattice] Update markConstantRange to return false equal ranges.

e30c257811f62fea21704caa961c61e4559de202 [CVP,SCCP] Precommit test for D75055.

4878aa36d4aa27df644430139fab2734fde4a000 [ValueLattice] Add new state for undef constants.

All patches except the last one apply cleanly. For the last one, the
changes to SCCP.cpp were stripped, because SCCP does not yet use
ValueLattice on release/10.x. Otherwise we would have to pull in more
additional changes.

Subscribers: tstellar, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76596

2 files changed, 10 insertions, 8 deletions

diff --git a/llvm/lib/Analysis/LazyValueInfo.cpp b/llvm/lib/Analysis/LazyValueInfo.cpp
index bad2de9e5f5..7ae7a1fd549 100644
--- a/llvm/lib/Analysis/LazyValueInfo.cpp
+++ b/llvm/lib/Analysis/LazyValueInfo.cpp
@@ -96,9 +96,9 @@ static ValueLatticeElement intersect(const ValueLatticeElement &A,
                                      const ValueLatticeElement &B) {
   // Undefined is the strongest state.  It means the value is known to be along
   // an unreachable path.
-  if (A.isUndefined())
+  if (A.isUnknown())
     return A;
-  if (B.isUndefined())
+  if (B.isUnknown())
     return B;
 
   // If we gave up for one, but got a useable fact from the other, use it.
@@ -1203,7 +1203,7 @@ static ValueLatticeElement getValueFromICmpCondition(Value *Val, ICmpInst *ICI,
       // false SETNE.
       if (isTrueDest == (Predicate == ICmpInst::ICMP_EQ))
         return ValueLatticeElement::get(cast<Constant>(RHS));
-      else
+      else if (!isa<UndefValue>(RHS))
         return ValueLatticeElement::getNot(cast<Constant>(RHS));
     }
   }
@@ -1722,7 +1722,7 @@ ConstantRange LazyValueInfo::getConstantRange(Value *V, BasicBlock *BB,
   const DataLayout &DL = BB->getModule()->getDataLayout();
   ValueLatticeElement Result =
       getImpl(PImpl, AC, &DL, DT).getValueInBlock(V, BB, CxtI);
-  if (Result.isUndefined())
+  if (Result.isUnknown())
     return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange())
     return Result.getConstantRange();
@@ -1761,7 +1761,7 @@ ConstantRange LazyValueInfo::getConstantRangeOnEdge(Value *V,
   ValueLatticeElement Result =
       getImpl(PImpl, AC, &DL, DT).getValueOnEdge(V, FromBB, ToBB, CxtI);
 
-  if (Result.isUndefined())
+  if (Result.isUnknown())
     return ConstantRange::getEmpty(Width);
   if (Result.isConstantRange())
     return Result.getConstantRange();
@@ -1991,7 +1991,7 @@ void LazyValueInfoAnnotatedWriter::emitBasicBlockStartAnnot(
   for (auto &Arg : F->args()) {
     ValueLatticeElement Result = LVIImpl->getValueInBlock(
         const_cast<Argument *>(&Arg), const_cast<BasicBlock *>(BB));
-    if (Result.isUndefined())
+    if (Result.isUnknown())
       continue;
     OS << "; LatticeVal for: '" << Arg << "' is: " << Result << "\n";
   }
diff --git a/llvm/lib/Analysis/ValueLattice.cpp b/llvm/lib/Analysis/ValueLattice.cpp
index a0115a0eec3..eaf8885cc14 100644
--- a/llvm/lib/Analysis/ValueLattice.cpp
+++ b/llvm/lib/Analysis/ValueLattice.cpp
@@ -10,8 +10,10 @@
 
 namespace llvm {
 raw_ostream &operator<<(raw_ostream &OS, const ValueLatticeElement &Val) {
-  if (Val.isUndefined())
-    return OS << "undefined";
+  if (Val.isUnknown())
+    return OS << "unknown";
+  if (Val.isUndef())
+    return OS << "undef";
   if (Val.isOverdefined())
     return OS << "overdefined";