[llvm] 094d129 - Revert "[ValueLattice] Fix getCompare() for undef values"

[Nikita Popov via llvm-commits]

Author: Nikita Popov
Date: 2022-11-01T17:03:40+01:00
New Revision: 094d1298d1a8c7eca942febf195fba0c1e54c3dc

URL: https://github.com/llvm/llvm-project/commit/094d1298d1a8c7eca942febf195fba0c1e54c3dc
DIFF: https://github.com/llvm/llvm-project/commit/094d1298d1a8c7eca942febf195fba0c1e54c3dc.diff

LOG: Revert "[ValueLattice] Fix getCompare() for undef values"

This reverts commit 6de41e6d7652b74a5aa2bd78b0597cc53a8c3c2a.

Missed a unit test affected by this change, revert for now.

Added: 
    

Modified: 
    llvm/include/llvm/Analysis/ValueLattice.h
    llvm/lib/Transforms/Utils/SCCPSolver.cpp

Removed: 
    


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diff  --git a/llvm/include/llvm/Analysis/ValueLattice.h b/llvm/include/llvm/Analysis/ValueLattice.h
index 7fe45d9f4dc96..bc6b279e9ed52 100644
--- a/llvm/include/llvm/Analysis/ValueLattice.h
+++ b/llvm/include/llvm/Analysis/ValueLattice.h
@@ -453,14 +453,8 @@ class ValueLatticeElement {
   /// evaluated.
   Constant *getCompare(CmpInst::Predicate Pred, Type *Ty,
                        const ValueLatticeElement &Other) const {
-    // Not yet resolved.
-    if (isUnknown() || Other.isUnknown())
-      return nullptr;
-
-    // TODO: Can be made more precise, but always returning undef would be
-    // incorrect.
-    if (isUndef() || isUndef())
-      return nullptr;
+    if (isUnknownOrUndef() || Other.isUnknownOrUndef())
+      return UndefValue::get(Ty);
 
     if (isConstant() && Other.isConstant())
       return ConstantExpr::getCompare(Pred, getConstant(), Other.getConstant());

diff  --git a/llvm/lib/Transforms/Utils/SCCPSolver.cpp b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
index 3d467f2fd68f9..a3455577a35c5 100644
--- a/llvm/lib/Transforms/Utils/SCCPSolver.cpp
+++ b/llvm/lib/Transforms/Utils/SCCPSolver.cpp
@@ -1044,6 +1044,9 @@ void SCCPInstVisitor::visitCmpInst(CmpInst &I) {
 
   Constant *C = V1State.getCompare(I.getPredicate(), I.getType(), V2State);
   if (C) {
+    // TODO: getCompare() currently has incorrect handling for unknown/undef.
+    if (isa<UndefValue>(C))
+      return;
     ValueLatticeElement CV;
     CV.markConstant(C);
     mergeInValue(&I, CV);