[InstSimplify] Expose generic interface for replaced operand simplification

[jdoerfert]

Summary

Users, especially the Attributor, might replace multiple operands at
once. The actual implementation of simplifyWithOpReplaced is able to
handle that just fine, the interface was simply not allowing to replace
more than one operand at a time. This is exposing a more generic
interface without intended changes for existing code.

[jdoerfert]

Rename function, improve documentation, clang format

[lebedev.ri]

llvm/include/llvm/Analysis/InstructionSimplify.h

328–333

[lebedev.ri]

llvm/include/llvm/Analysis/InstructionSimplify.h

332

Should this be ArrayRef?

[jdoerfert]

Use ArrayRef

[nikic]

I don't think simplifyWithOpReplaced() is the right starting point for this. This function has a specific purpose and it has complex and dangerous semantics.

I think what you really want is something along the lines of ConstantFoldInstruction vs ConstantFoldInstOperands. That is, you should take SimplifyInstruction and rewrite it into a SimplifyInstOperands function that takes the operands as an explicit ArrayRef, and then call that from SimplifyInstruction. That will ensure that you can actually simplify all instructions that InstSimplify supports, rather than just the peculiar subset that simplifyWithOpReplaced deals with.

[lebedev.ri]

Seems straight-forward to me

[jdoerfert]

Working on the alternative

llvm/include/llvm/Analysis/InstructionSimplify.h

332

Yes.

[jdoerfert]

Change approach to use the SimplifyInstruction interface instead. Tests not updated yet.

[jdoerfert]

@nikic Like this?

I needed to use NewOps for load simplification to make it as powerful as the former approach. Also did the same to PHI simplification because it seemed easy.

[lebedev.ri]

simplifyInstruction*With*Operands

[nikic]

LG

llvm/lib/Analysis/InstructionSimplify.cpp

6051–6055

make the load

6081

This fallback shouldn't be necessary, ConstantFoldInstruction bails on non-constant operands.

[jdoerfert]

Address comments

[lebedev.ri]

Not sure if it makes sense to commit some parts of this separately, maybe not.

llvm/lib/Analysis/InstructionSimplify.cpp

6221–6222

assert(NewOps.size() == I.getNumOperands() && "");

[jdoerfert]

Add assert

llvm/include/llvm/Analysis/InstructionSimplify.h

struct SimplifyQuery {
   }
 };
 
 // NOTE: the explicit multiple argument versions of these functions are
 // deprecated.
 // Please use the SimplifyQuery versions in new code.
 
 /// Given operand for an FNeg, fold the result or return null.
-Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF,
-                        const SimplifyQuery &Q);
+Value *SimplifyFNegInst(Value *Op, FastMathFlags FMF, const SimplifyQuery &Q);
 
 /// Given operands for an Add, fold the result or return null.
 Value *SimplifyAddInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
                        const SimplifyQuery &Q);
 
 /// Given operands for a Sub, fold the result or return null.
 Value *SimplifySubInst(Value *LHS, Value *RHS, bool isNSW, bool isNUW,
                        const SimplifyQuery &Q);
Value *SimplifyUnOp(unsigned Opcode, Value *Op, FastMathFlags FMF,
                     const SimplifyQuery &Q);
 
 /// Given operands for a BinaryOperator, fold the result or return null.
 Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
                      const SimplifyQuery &Q);
 
 /// Given operands for a BinaryOperator, fold the result or return null.
 /// Try to use FastMathFlags when folding the result.
-Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS,
-                     FastMathFlags FMF, const SimplifyQuery &Q);
+Value *SimplifyBinOp(unsigned Opcode, Value *LHS, Value *RHS, FastMathFlags FMF,
+                     const SimplifyQuery &Q);
 
 /// Given a callsite, fold the result or return null.
 Value *SimplifyCall(CallBase *Call, const SimplifyQuery &Q);
 
 /// Given an operand for a Freeze, see if we can fold the result.
 /// If not, this returns null.
 Value *SimplifyFreezeInst(Value *Op, const SimplifyQuery &Q);
 
 /// See if we can compute a simplified version of this instruction. If not,
 /// return null.
 Value *SimplifyInstruction(Instruction *I, const SimplifyQuery &Q,
                            OptimizationRemarkEmitter *ORE = nullptr);
 
+/// Like \p SimplifyInstruction but the operands of \p I are replaced with
+/// \p NewOps. Returns a simplified value, or null if none was found.
+Value *
+SimplifyInstructionWithOperands(Instruction *I, ArrayRef<Value *> NewOps,
+                                const SimplifyQuery &Q,
+                                OptimizationRemarkEmitter *ORE = nullptr);
+
 /// See if V simplifies when its operand Op is replaced with RepOp. If not,
 /// return null.
 /// AllowRefinement specifies whether the simplification can be a refinement
 /// (e.g. 0 instead of poison), or whether it needs to be strictly identical.
 Value *simplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
                               const SimplifyQuery &Q, bool AllowRefinement);
 
 /// Replace all uses of 'I' with 'SimpleV' and simplify the uses recursively.
 ///
 /// This first performs a normal RAUW of I with SimpleV. It then recursively
 /// attempts to simplify those users updated by the operation. The 'I'
 /// instruction must not be equal to the simplified value 'SimpleV'.
 /// If UnsimplifiedUsers is provided, instructions that could not be simplified
 /// are added to it.
 ///
 /// The function returns true if any simplifications were performed.
 bool replaceAndRecursivelySimplify(
     Instruction *I, Value *SimpleV, const TargetLibraryInfo *TLI = nullptr,
     const DominatorTree *DT = nullptr, AssumptionCache *AC = nullptr,
     SmallSetVector<Instruction *, 8> *UnsimplifiedUsers = nullptr);
 
 // These helper functions return a SimplifyQuery structure that contains as
 // many of the optional analysis we use as are currently valid.  This is the
 // strongly preferred way of constructing SimplifyQuery in passes.
 const SimplifyQuery getBestSimplifyQuery(Pass &, Function &);
 template <class T, class... TArgs>
 const SimplifyQuery getBestSimplifyQuery(AnalysisManager<T, TArgs...> &,
                                          Function &);
 const SimplifyQuery getBestSimplifyQuery(LoopStandardAnalysisResults &,
                                          const DataLayout &);
 } // end namespace llvm
 
 #endif
-

llvm/lib/Analysis/InstructionSimplify.cpp

 // returning a constant ("and i32 %x, 0" -> "0") or an already existing value
 // ("and i32 %x, %x" -> "%x").  All operands are assumed to have already been
 // simplified: This is usually true and assuming it simplifies the logic (if
 // they have not been simplified then results are correct but maybe suboptimal).
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/InstructionSimplify.h"
+
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/CaptureTracking.h"
 #include "llvm/Analysis/CmpInstAnalysis.h"
 #include "llvm/Analysis/ConstantFolding.h"

 }
 
 Value *llvm::SimplifyExtractElementInst(Value *Vec, Value *Idx,
                                         const SimplifyQuery &Q) {
   return ::SimplifyExtractElementInst(Vec, Idx, Q, RecursionLimit);
 }
 
 /// See if we can fold the given phi. If not, returns null.
-static Value *SimplifyPHINode(PHINode *PN, const SimplifyQuery &Q) {
+static Value *SimplifyPHINode(PHINode *PN, ArrayRef<Value *> IncomingValues,
+                              const SimplifyQuery &Q) {
   // WARNING: no matter how worthwhile it may seem, we can not perform PHI CSE
   //          here, because the PHI we may succeed simplifying to was not
   //          def-reachable from the original PHI!
 
   // If all of the PHI's incoming values are the same then replace the PHI node
   // with the common value.
   Value *CommonValue = nullptr;
   bool HasUndefInput = false;
-  for (Value *Incoming : PN->incoming_values()) {
+  for (Value *Incoming : IncomingValues) {
     // If the incoming value is the phi node itself, it can safely be skipped.
     if (Incoming == PN) continue;
     if (Q.isUndefValue(Incoming)) {
       // Remember that we saw an undef value, but otherwise ignore them.
       HasUndefInput = true;
       continue;
     }
     if (CommonValue && Incoming != CommonValue)
if (isa<BitCastOperator>(CurOp)) {
              cast<IntrinsicInst>(CurOp)->isLaunderOrStripInvariantGroup() &&
              "expected invariant group intrinsic");
       NewOp = ConstantExpr::getBitCast(NewOp, CurOp->getType());
     }
   }
   return NewOp;
 }
 
-static Value *SimplifyLoadInst(LoadInst *LI, const SimplifyQuery &Q) {
+static Value *SimplifyLoadInst(LoadInst *LI, Value *PtrOp,
+                               const SimplifyQuery &Q) {
   if (LI->isVolatile())
     return nullptr;
 
-  if (auto *C = ConstantFoldInstruction(LI, Q.DL))
-    return C;
+  // Try to make the load operand a constant, specifically handle
+  // invariant.group intrinsics.
+  auto *PtrOpC = dyn_cast<Constant>(PtrOp);
+  if (!PtrOpC)
+    PtrOpC = ConstructLoadOperandConstant(PtrOp);
 
-  // The following only catches more cases than ConstantFoldInstruction() if the
-  // load operand wasn't a constant. Specifically, invariant.group intrinsics.
-  if (isa<Constant>(LI->getPointerOperand()))
-    return nullptr;
-
-  if (auto *C = dyn_cast_or_null<Constant>(
-          ConstructLoadOperandConstant(LI->getPointerOperand())))
-    return ConstantFoldLoadFromConstPtr(C, LI->getType(), Q.DL);
+  if (PtrOpC)
+    return ConstantFoldLoadFromConstPtr(PtrOpC, LI->getType(), Q.DL);
 
   return nullptr;
 }
 
 /// See if we can compute a simplified version of this instruction.
 /// If not, this returns null.
 
-Value *llvm::SimplifyInstruction(Instruction *I, const SimplifyQuery &SQ,
+static Value *simplifyInstructionWithOperands(Instruction *I,
+                                              ArrayRef<Value *> NewOps,
+                                              const SimplifyQuery &SQ,
                                               OptimizationRemarkEmitter *ORE) {
   const SimplifyQuery Q = SQ.CxtI ? SQ : SQ.getWithInstruction(I);
-  Value *Result;
+  Value *Result = nullptr;
 
   switch (I->getOpcode()) {
   default:
-    Result = ConstantFoldInstruction(I, Q.DL, Q.TLI);
+    if (llvm::all_of(NewOps, [](Value *V) { return isa<Constant>(V); })) {
+      SmallVector<Constant *, 8> NewConstOps(NewOps.size());
+      transform(NewOps, NewConstOps.begin(),
+                [](Value *V) { return cast<Constant>(V); });
+      Result = ConstantFoldInstOperands(I, NewConstOps, Q.DL, Q.TLI);
+    }
     break;
   case Instruction::FNeg:
-    Result = SimplifyFNegInst(I->getOperand(0), I->getFastMathFlags(), Q);
+    Result = SimplifyFNegInst(NewOps[0], I->getFastMathFlags(), Q);
     break;
   case Instruction::FAdd:
-    Result = SimplifyFAddInst(I->getOperand(0), I->getOperand(1),
-                              I->getFastMathFlags(), Q);
+    Result = SimplifyFAddInst(NewOps[0], NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::Add:
-    Result =
-        SimplifyAddInst(I->getOperand(0), I->getOperand(1),
-                        Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
-                        Q.IIQ.hasNoUnsignedWrap(cast<BinaryOperator>(I)), Q);
+    Result = SimplifyAddInst(
+        NewOps[0], NewOps[1], Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
     break;
   case Instruction::FSub:
-    Result = SimplifyFSubInst(I->getOperand(0), I->getOperand(1),
-                              I->getFastMathFlags(), Q);
+    Result = SimplifyFSubInst(NewOps[0], NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::Sub:
-    Result =
-        SimplifySubInst(I->getOperand(0), I->getOperand(1),
-                        Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
-                        Q.IIQ.hasNoUnsignedWrap(cast<BinaryOperator>(I)), Q);
+    Result = SimplifySubInst(
+        NewOps[0], NewOps[1], Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
     break;
   case Instruction::FMul:
-    Result = SimplifyFMulInst(I->getOperand(0), I->getOperand(1),
-                              I->getFastMathFlags(), Q);
+    Result = SimplifyFMulInst(NewOps[0], NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::Mul:
-    Result = SimplifyMulInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyMulInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::SDiv:
-    Result = SimplifySDivInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifySDivInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::UDiv:
-    Result = SimplifyUDivInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyUDivInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::FDiv:
-    Result = SimplifyFDivInst(I->getOperand(0), I->getOperand(1),
-                              I->getFastMathFlags(), Q);
+    Result = SimplifyFDivInst(NewOps[0], NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::SRem:
-    Result = SimplifySRemInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifySRemInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::URem:
-    Result = SimplifyURemInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyURemInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::FRem:
-    Result = SimplifyFRemInst(I->getOperand(0), I->getOperand(1),
-                              I->getFastMathFlags(), Q);
+    Result = SimplifyFRemInst(NewOps[0], NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::Shl:
-    Result =
-        SimplifyShlInst(I->getOperand(0), I->getOperand(1),
-                        Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
-                        Q.IIQ.hasNoUnsignedWrap(cast<BinaryOperator>(I)), Q);
+    Result = SimplifyShlInst(
+        NewOps[0], NewOps[1], Q.IIQ.hasNoSignedWrap(cast<BinaryOperator>(I)),
     break;
   case Instruction::LShr:
-    Result = SimplifyLShrInst(I->getOperand(0), I->getOperand(1),
+    Result = SimplifyLShrInst(NewOps[0], NewOps[1],
                               Q.IIQ.isExact(cast<BinaryOperator>(I)), Q);
     break;
   case Instruction::AShr:
-    Result = SimplifyAShrInst(I->getOperand(0), I->getOperand(1),
+    Result = SimplifyAShrInst(NewOps[0], NewOps[1],
                               Q.IIQ.isExact(cast<BinaryOperator>(I)), Q);
     break;
   case Instruction::And:
-    Result = SimplifyAndInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyAndInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::Or:
-    Result = SimplifyOrInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyOrInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::Xor:
-    Result = SimplifyXorInst(I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyXorInst(NewOps[0], NewOps[1], Q);
     break;
   case Instruction::ICmp:
-    Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(),
-                              I->getOperand(0), I->getOperand(1), Q);
+    Result = SimplifyICmpInst(cast<ICmpInst>(I)->getPredicate(), NewOps[0],
+                              NewOps[1], Q);
     break;
   case Instruction::FCmp:
-    Result =
-        SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), I->getOperand(0),
-                         I->getOperand(1), I->getFastMathFlags(), Q);
+    Result = SimplifyFCmpInst(cast<FCmpInst>(I)->getPredicate(), NewOps[0],
+                              NewOps[1], I->getFastMathFlags(), Q);
     break;
   case Instruction::Select:
-    Result = SimplifySelectInst(I->getOperand(0), I->getOperand(1),
-                                I->getOperand(2), Q);
+    Result = SimplifySelectInst(NewOps[0], NewOps[1], NewOps[2], Q);
     break;
   case Instruction::GetElementPtr: {
-    SmallVector<Value *, 8> Ops(I->operands());
     Result = SimplifyGEPInst(cast<GetElementPtrInst>(I)->getSourceElementType(),
-                             Ops, Q);
+                             NewOps, Q);
     break;
   }
   case Instruction::InsertValue: {
     InsertValueInst *IV = cast<InsertValueInst>(I);
-    Result = SimplifyInsertValueInst(IV->getAggregateOperand(),
-                                     IV->getInsertedValueOperand(),
-                                     IV->getIndices(), Q);
+    Result = SimplifyInsertValueInst(NewOps[0], NewOps[1], IV->getIndices(), Q);
     break;
   }
   case Instruction::InsertElement: {
-    auto *IE = cast<InsertElementInst>(I);
-    Result = SimplifyInsertElementInst(IE->getOperand(0), IE->getOperand(1),
-                                       IE->getOperand(2), Q);
+    Result = SimplifyInsertElementInst(NewOps[0], NewOps[1], NewOps[2], Q);
     break;
   }
   case Instruction::ExtractValue: {
     auto *EVI = cast<ExtractValueInst>(I);
-    Result = SimplifyExtractValueInst(EVI->getAggregateOperand(),
-                                      EVI->getIndices(), Q);
+    Result = SimplifyExtractValueInst(NewOps[0], EVI->getIndices(), Q);
     break;
   }
   case Instruction::ExtractElement: {
-    auto *EEI = cast<ExtractElementInst>(I);
-    Result = SimplifyExtractElementInst(EEI->getVectorOperand(),
-                                        EEI->getIndexOperand(), Q);
+    Result = SimplifyExtractElementInst(NewOps[0], NewOps[1], Q);
     break;
   }
   case Instruction::ShuffleVector: {
     auto *SVI = cast<ShuffleVectorInst>(I);
-    Result =
-        SimplifyShuffleVectorInst(SVI->getOperand(0), SVI->getOperand(1),
-                                  SVI->getShuffleMask(), SVI->getType(), Q);
+    Result = SimplifyShuffleVectorInst(
+        NewOps[0], NewOps[1], SVI->getShuffleMask(), SVI->getType(), Q);
     break;
   }
   case Instruction::PHI:
-    Result = SimplifyPHINode(cast<PHINode>(I), Q);
+    Result = SimplifyPHINode(cast<PHINode>(I), NewOps, Q);
     break;
   case Instruction::Call: {
+    // TODO: Use NewOps
     Result = SimplifyCall(cast<CallInst>(I), Q);
     break;
   }
   case Instruction::Freeze:
-    Result = SimplifyFreezeInst(I->getOperand(0), Q);
+    Result = llvm::SimplifyFreezeInst(NewOps[0], Q);
     break;
 #define HANDLE_CAST_INST(num, opc, clas) case Instruction::opc:
 #include "llvm/IR/Instruction.def"
 #undef HANDLE_CAST_INST
-    Result =
-        SimplifyCastInst(I->getOpcode(), I->getOperand(0), I->getType(), Q);
+    Result = SimplifyCastInst(I->getOpcode(), NewOps[0], I->getType(), Q);
     break;
   case Instruction::Alloca:
     // No simplifications for Alloca and it can't be constant folded.
     Result = nullptr;
     break;
   case Instruction::Load:
-    Result = SimplifyLoadInst(cast<LoadInst>(I), Q);
+    Result = SimplifyLoadInst(cast<LoadInst>(I), NewOps[0], Q);
     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 a safe value instead.
   return Result == I ? UndefValue::get(I->getType()) : Result;
 }
 
+Value *llvm::SimplifyInstructionWithOperands(Instruction *I,
+                                             ArrayRef<Value *> NewOps,
+                                             const SimplifyQuery &SQ,
+                                             OptimizationRemarkEmitter *ORE) {
+  assert(NewOps.size() == I->getNumOperands() &&
+         "Number of operands should match the instruction!");
+  return ::simplifyInstructionWithOperands(I, NewOps, SQ, ORE);
+}
+
+Value *llvm::SimplifyInstruction(Instruction *I, const SimplifyQuery &SQ,
+                                 OptimizationRemarkEmitter *ORE) {
+  SmallVector<Value *, 8> Ops(I->operands());
+  return ::simplifyInstructionWithOperands(I, Ops, SQ, ORE);
+}
+
 /// Implementation of recursive simplification through an instruction's
 /// uses.
 ///
 /// This is the common implementation of the recursive simplification routines.
 /// If we have a pre-simplified value in 'SimpleV', that is forcibly used to
 /// replace the instruction 'I'. Otherwise, we simply add 'I' to the list of
 /// instructions to process and attempt to simplify it using
 /// InstructionSimplify. Recursively visited users which could not be