[llvm] db870cf - [InstCombine] Extract helper from matchFunnelShift (NFC)

[Nikita Popov via llvm-commits]

Author: Eikansh Gupta
Date: 2024-02-16T16:46:41+01:00
New Revision: db870cfc9ed20e810308262d6d6bbb08b369c23f

URL: https://github.com/llvm/llvm-project/commit/db870cfc9ed20e810308262d6d6bbb08b369c23f
DIFF: https://github.com/llvm/llvm-project/commit/db870cfc9ed20e810308262d6d6bbb08b369c23f.diff

LOG: [InstCombine] Extract helper from matchFunnelShift (NFC)

The matchFunnelShift function was doing pattern matching and creating
the fshl/fshr instruction if needed. Moved the pattern matching code to
function convertOrOfShiftsToFunnelShift. It can be reused for other
optimizations.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    llvm/lib/Transforms/InstCombine/InstCombineInternal.h

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 0af9a2786f6901..43a99fc476e823 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -2808,17 +2808,18 @@ Instruction *InstCombinerImpl::matchBSwapOrBitReverse(Instruction &I,
   return LastInst;
 }
 
-/// Match UB-safe variants of the funnel shift intrinsic.
-static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
-                                     const DominatorTree &DT) {
+std::optional<std::pair<Intrinsic::ID, SmallVector<Value *, 3>>>
+InstCombinerImpl::convertOrOfShiftsToFunnelShift(Instruction &Or) {
   // TODO: Can we reduce the code duplication between this and the related
   // rotate matching code under visitSelect and visitTrunc?
+  assert(Or.getOpcode() == BinaryOperator::Or && "Expecting or instruction");
+
   unsigned Width = Or.getType()->getScalarSizeInBits();
 
   Instruction *Or0, *Or1;
   if (!match(Or.getOperand(0), m_Instruction(Or0)) ||
       !match(Or.getOperand(1), m_Instruction(Or1)))
-    return nullptr;
+    return std::nullopt;
 
   bool IsFshl = true; // Sub on LSHR.
   SmallVector<Value *, 3> FShiftArgs;
@@ -2832,7 +2833,7 @@ static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
         !match(Or1,
                m_OneUse(m_LogicalShift(m_Value(ShVal1), m_Value(ShAmt1)))) ||
         Or0->getOpcode() == Or1->getOpcode())
-      return nullptr;
+      return std::nullopt;
 
     // Canonicalize to or(shl(ShVal0, ShAmt0), lshr(ShVal1, ShAmt1)).
     if (Or0->getOpcode() == BinaryOperator::LShr) {
@@ -2868,7 +2869,7 @@ static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
       // might remove it after this fold). This still doesn't guarantee that the
       // final codegen will match this original pattern.
       if (match(R, m_OneUse(m_Sub(m_SpecificInt(Width), m_Specific(L))))) {
-        KnownBits KnownL = IC.computeKnownBits(L, /*Depth*/ 0, &Or);
+        KnownBits KnownL = computeKnownBits(L, /*Depth*/ 0, &Or);
         return KnownL.getMaxValue().ult(Width) ? L : nullptr;
       }
 
@@ -2916,7 +2917,7 @@ static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
       IsFshl = false; // Sub on SHL.
     }
     if (!ShAmt)
-      return nullptr;
+      return std::nullopt;
 
     FShiftArgs = {ShVal0, ShVal1, ShAmt};
   } else if (isa<ZExtInst>(Or0) || isa<ZExtInst>(Or1)) {
@@ -2938,18 +2939,18 @@ static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
     const APInt *ZextHighShlAmt;
     if (!match(Or0,
                m_OneUse(m_Shl(m_Value(ZextHigh), m_APInt(ZextHighShlAmt)))))
-      return nullptr;
+      return std::nullopt;
 
     if (!match(Or1, m_ZExt(m_Value(Low))) ||
         !match(ZextHigh, m_ZExt(m_Value(High))))
-      return nullptr;
+      return std::nullopt;
 
     unsigned HighSize = High->getType()->getScalarSizeInBits();
     unsigned LowSize = Low->getType()->getScalarSizeInBits();
     // Make sure High does not overlap with Low and most significant bits of
     // High aren't shifted out.
     if (ZextHighShlAmt->ult(LowSize) || ZextHighShlAmt->ugt(Width - HighSize))
-      return nullptr;
+      return std::nullopt;
 
     for (User *U : ZextHigh->users()) {
       Value *X, *Y;
@@ -2980,11 +2981,21 @@ static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC,
   }
 
   if (FShiftArgs.empty())
-    return nullptr;
+    return std::nullopt;
 
   Intrinsic::ID IID = IsFshl ? Intrinsic::fshl : Intrinsic::fshr;
-  Function *F = Intrinsic::getDeclaration(Or.getModule(), IID, Or.getType());
-  return CallInst::Create(F, FShiftArgs);
+  return std::make_pair(IID, FShiftArgs);
+}
+
+/// Match UB-safe variants of the funnel shift intrinsic.
+static Instruction *matchFunnelShift(Instruction &Or, InstCombinerImpl &IC) {
+  if (auto Opt = IC.convertOrOfShiftsToFunnelShift(Or)) {
+    auto [IID, FShiftArgs] = *Opt;
+    Function *F = Intrinsic::getDeclaration(Or.getModule(), IID, Or.getType());
+    return CallInst::Create(F, FShiftArgs);
+  }
+
+  return nullptr;
 }
 
 /// Attempt to combine or(zext(x),shl(zext(y),bw/2) concat packing patterns.
@@ -3475,7 +3486,7 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
                                                   /*MatchBitReversals*/ true))
     return BitOp;
 
-  if (Instruction *Funnel = matchFunnelShift(I, *this, DT))
+  if (Instruction *Funnel = matchFunnelShift(I, *this))
     return Funnel;
 
   if (Instruction *Concat = matchOrConcat(I, Builder))

diff  --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index 7f6618fc5b737c..0b4283bc37650a 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -237,6 +237,9 @@ class LLVM_LIBRARY_VISIBILITY InstCombinerImpl final
     return getLosslessTrunc(C, TruncTy, Instruction::SExt);
   }
 
+  std::optional<std::pair<Intrinsic::ID, SmallVector<Value *, 3>>>
+  convertOrOfShiftsToFunnelShift(Instruction &Or);
+
 private:
   bool annotateAnyAllocSite(CallBase &Call, const TargetLibraryInfo *TLI);
   bool isDesirableIntType(unsigned BitWidth) const;