[PredicateInfo] Support existing PredicateType by adding PredicatePHI

when needing introduction of phi nodes

Resolves #150606

Currently `ssa.copy` is used mostly for straight line code, i.e, without
joins or uses of phi nodes. With this, passes would be able to pick up the
relevant info and further optimize the IR.

Author: Rajveer100

llvm/include/llvm/Transforms/Utils/PredicateInfo.h

@@ -67,7 +67,7 @@ class Value;
 class IntrinsicInst;
 class raw_ostream;
 
-enum PredicateType { PT_Branch, PT_Assume, PT_Switch };
+enum PredicateType { PT_Branch, PT_Assume, PT_Switch, PT_PHI };
 
 /// Constraint for a predicate of the form "cmp Pred Op, OtherOp", where Op
 /// is the value the constraint applies to (the ssa.copy result).
@@ -171,6 +171,16 @@ class PredicateSwitch : public PredicateWithEdge {
   }
 };
 
+class PredicatePHI : public PredicateBase {
+public:
+  BasicBlock *PHIBlock;
+  SmallVector<std::pair<BasicBlock *, PredicateBase *>, 4> IncomingPredicates;
+
+  PredicatePHI(Value *Op, BasicBlock *PHIBB)
+      : PredicateBase(PT_PHI, Op, nullptr), PHIBlock(PHIBB) {}
+  static bool classof(const PredicateBase *PB) { return PB->Type == PT_PHI; }
+};
+
 /// Encapsulates PredicateInfo, including all data associated with memory
 /// accesses.
 class PredicateInfo {

llvm/lib/Transforms/Utils/PredicateInfo.cpp

@@ -15,6 +15,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/Analysis/AssumptionCache.h"
+#include "llvm/Analysis/IteratedDominanceFrontier.h"
 #include "llvm/IR/AssemblyAnnotationWriter.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IRBuilder.h"
@@ -213,6 +214,8 @@ class PredicateInfoBuilder {
   // whether it returned a valid result.
   DenseMap<Value *, unsigned int> ValueInfoNums;
 
+  DenseMap<BasicBlock *, SmallVector<Value *, 4>> PHICandidates;
+
   BumpPtrAllocator &Allocator;
 
   ValueInfo &getOrCreateValueInfo(Value *);
@@ -478,6 +481,9 @@ void PredicateInfoBuilder::buildPredicateInfo() {
       if (DT.isReachableFromEntry(II->getParent()))
         processAssume(II, II->getParent(), OpsToRename);
   }
+
+  // ...
+
   // Now rename all our operations.
   renameUses(OpsToRename);
 }
@@ -773,6 +779,8 @@ std::optional<PredicateConstraint> PredicateBase::getConstraint() const {
     }
 
     return {{CmpInst::ICMP_EQ, cast<PredicateSwitch>(this)->CaseValue}};
+  case PT_PHI:
+    return cast<PredicatePHI>(this)->getConstraint();
   }
   llvm_unreachable("Unknown predicate type");
 }
@@ -838,6 +846,10 @@ class PredicateInfoAnnotatedWriter : public AssemblyAnnotationWriter {
       } else if (const auto *PA = dyn_cast<PredicateAssume>(PI)) {
         OS << "; assume predicate info {"
            << " Comparison:" << *PA->Condition;
+      } else if (const auto *PP = dyn_cast<PredicatePHI>(PI)) {
+        OS << "; phi predicate info { PHIBlock: ";
+        PP->PHIBlock->printAsOperand(OS);
+        OS << " IncomingEdges: " << PP->IncomingPredicates.size();
       }
       OS << ", RenamedOp: ";
       PI->RenamedOp->printAsOperand(OS, false);