Commit 843c0adf authored by Jay Foad's avatar Jay Foad
Browse files

[ConstantFold] Fold extractelement of getelementptr 

Summary:
Getelementptr has vector type if any of its operands are vectors
(the scalar operands being implicitly broadcast to all vector elements).
Extractelement applied to a vector getelementptr can be folded by
applying the extractelement in turn to all of the vector operands.

Subscribers: hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69379
parent f2132070

llvm/lib/IR/ConstantFold.cpp

+29 −6
Original line number Diff line number Diff line
@@ -792,13 +792,36 @@ Constant *llvm::ConstantFoldExtractElementInstruction(Constant *Val, 
  if (isa<UndefValue>(Val) || isa<UndefValue>(Idx))

    return UndefValue::get(Val->getType()->getVectorElementType());



  if (ConstantInt *CIdx = dyn_cast<ConstantInt>(Idx)) {

  auto *CIdx = dyn_cast<ConstantInt>(Idx);

  if (!CIdx)

    return nullptr;



  // ee({w,x,y,z}, wrong_value) -> undef

  if (CIdx->uge(Val->getType()->getVectorNumElements()))

    return UndefValue::get(Val->getType()->getVectorElementType());

    return Val->getAggregateElement(CIdx->getZExtValue());

  }



  // ee (gep (ptr, idx0, ...), idx) -> gep (ee (ptr, idx), ee (idx0, idx), ...)

  if (auto *CE = dyn_cast<ConstantExpr>(Val)) {

    if (CE->getOpcode() == Instruction::GetElementPtr) {

      SmallVector<Constant *, 8> Ops;

      Ops.reserve(CE->getNumOperands());

      for (unsigned i = 0, e = CE->getNumOperands(); i != e; ++i) {

        Constant *Op = CE->getOperand(i);

        if (Op->getType()->isVectorTy()) {

          Constant *ScalarOp = ConstantFoldExtractElementInstruction(Op, Idx);

          if (!ScalarOp)

            return  nullptr;

          Ops.push_back(ScalarOp);

        } else

          Ops.push_back(Op);

      }

      return CE->getWithOperands(Ops, CE->getType()->getVectorElementType(),

                                 false,

                                 Ops[0]->getType()->getPointerElementType());

    }

  }



  return Val->getAggregateElement(CIdx);

}



Constant *llvm::ConstantFoldInsertElementInstruction(Constant *Val,

llvm/test/Analysis/ConstantFolding/gep-zeroinit-vector.ll

+1 −1
Original line number Diff line number Diff line
@@ -9,7 +9,7 @@ 


define <2 x i16*> @test_gep() {

; CHECK-LABEL: @test_gep(

; CHECK-NEXT:    ret <2 x i16*> <i16* getelementptr inbounds (%rec8, %rec8* extractelement (<2 x %rec8*> getelementptr ([1 x %rec8], [1 x %rec8]* @a, <2 x i64> zeroinitializer, <2 x i64> zeroinitializer), i32 0), i32 0, i32 0), i16* getelementptr inbounds (%rec8, %rec8* extractelement (<2 x %rec8*> getelementptr ([1 x %rec8], [1 x %rec8]* @a, <2 x i64> zeroinitializer, <2 x i64> zeroinitializer), i32 1), i32 0, i32 0)>

; CHECK-NEXT:    ret <2 x i16*> <i16* getelementptr inbounds ([1 x %rec8], [1 x %rec8]* @a, i32 0, i32 0, i32 0), i16* getelementptr inbounds ([1 x %rec8], [1 x %rec8]* @a, i32 0, i32 0, i32 0)>

;

  %A = getelementptr [1 x %rec8], [1 x %rec8]* @a, <2 x i16> zeroinitializer, <2 x i64> zeroinitializer

  %B = bitcast <2 x %rec8*> %A to <2 x i16*>

llvm/test/Transforms/InstCombine/vec_demanded_elts.ll

+1 −1
Original line number Diff line number Diff line
@@ -569,7 +569,7 @@ define i32* @gep_cvbase_w_s_idx(<2 x i32*> %base, i64 %raw_addr) { 


define i32* @gep_cvbase_w_cv_idx(<2 x i32*> %base, i64 %raw_addr) {

; CHECK-LABEL: @gep_cvbase_w_cv_idx(

; CHECK-NEXT:    ret i32* extractelement (<2 x i32*> getelementptr (i32, <2 x i32*> <i32* @GLOBAL, i32* @GLOBAL>, <2 x i64> <i64 0, i64 1>), i32 1)

; CHECK-NEXT:    ret i32* getelementptr inbounds (i32, i32* @GLOBAL, i64 1)

;

  %gep = getelementptr i32, <2 x i32*> <i32* @GLOBAL, i32* @GLOBAL>, <2 x i64> <i64 0, i64 1>

  %ee = extractelement <2 x i32*> %gep, i32 1

llvm/test/Transforms/LoopVectorize/X86/constant-fold.ll

+1 −1
Original line number Diff line number Diff line
@@ -27,7 +27,7 @@ define void @f1() { 
; CHECK-NEXT:    [[TMP2:%.*]] = getelementptr [2 x i16*], [2 x i16*]* @b, i16 0, i64 [[TMP1]]

; CHECK-NEXT:    [[TMP3:%.*]] = getelementptr i16*, i16** [[TMP2]], i32 0

; CHECK-NEXT:    [[TMP4:%.*]] = bitcast i16** [[TMP3]] to <2 x i16*>*

; CHECK-NEXT:    store <2 x i16*> <i16* getelementptr inbounds (%rec8, %rec8* extractelement (<2 x %rec8*> getelementptr ([1 x %rec8], [1 x %rec8]* @a, <2 x i16> zeroinitializer, <2 x i64> zeroinitializer), i32 0), i32 0, i32 0), i16* getelementptr inbounds (%rec8, %rec8* extractelement (<2 x %rec8*> getelementptr ([1 x %rec8], [1 x %rec8]* @a, <2 x i16> zeroinitializer, <2 x i64> zeroinitializer), i32 1), i32 0, i32 0)>, <2 x i16*>* [[TMP4]], align 8

; CHECK-NEXT:    store <2 x i16*> <i16* getelementptr inbounds ([1 x %rec8], [1 x %rec8]* @a, i32 0, i32 0, i32 0), i16* getelementptr inbounds ([1 x %rec8], [1 x %rec8]* @a, i32 0, i32 0, i32 0)>, <2 x i16*>* [[TMP4]], align 8

; CHECK-NEXT:    [[INDEX_NEXT]] = add i32 [[INDEX]], 2

; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[INDEX_NEXT]], 2

; CHECK-NEXT:    br i1 [[TMP5]], label [[MIDDLE_BLOCK:%.*]], label [[VECTOR_BODY]], !llvm.loop !0