[ConstExpr] Remove select constant expression

This removes the select constant expression, as part of
https://discourse.llvm.org/t/rfc-remove-most-constant-expressions/63179.
Uses of this expressions have already been removed in advance,
so this just removes related infrastructure and updates tests.

Differential Revision: https://reviews.llvm.org/D145382

llvm/bindings/ocaml/llvm/llvm.ml

@@ -685,8 +685,6 @@ external const_pointercast : llvalue -> lltype -> llvalue
 external const_intcast : llvalue -> lltype -> is_signed:bool -> llvalue
                        = "llvm_const_intcast"
 external const_fpcast : llvalue -> lltype -> llvalue = "llvm_const_fpcast"
-external const_select : llvalue -> llvalue -> llvalue -> llvalue
-                      = "llvm_const_select"
 external const_extractelement : llvalue -> llvalue -> llvalue
                               = "llvm_const_extractelement"
 external const_insertelement : llvalue -> llvalue -> llvalue -> llvalue

llvm/bindings/ocaml/llvm/llvm.mli

@@ -1268,11 +1268,6 @@ val const_intcast : llvalue -> lltype -> is_signed:bool -> llvalue
     See the method [llvm::ConstantExpr::getFPCast]. *)
 val const_fpcast : llvalue -> lltype -> llvalue
 
-(** [const_select cond t f] returns the constant conditional which returns value
-    [t] if the boolean constant [cond] is true and the value [f] otherwise.
-    See the method [llvm::ConstantExpr::getSelect]. *)
-val const_select : llvalue -> llvalue -> llvalue -> llvalue
-
 (** [const_extractelement vec i] returns the constant [i]th element of
     constant vector [vec]. [i] must be a constant [i32] value unsigned less than
     the size of the vector.

llvm/bindings/ocaml/llvm/llvm_ocaml.c

@@ -1385,13 +1385,6 @@ value llvm_const_fpcast(value CV, value T) {
   return to_val(Value);
 }
 
-/* llvalue -> llvalue -> llvalue -> llvalue */
-value llvm_const_select(value Cond, value IfTrue, value IfFalse) {
-  LLVMValueRef Value =
-      LLVMConstSelect(Value_val(Cond), Value_val(IfTrue), Value_val(IfFalse));
-  return to_val(Value);
-}
-
 /* llvalue -> llvalue -> llvalue */
 value llvm_const_extractelement(value V, value I) {
   LLVMValueRef Value = LLVMConstExtractElement(Value_val(V), Value_val(I));

llvm/docs/ReleaseNotes.rst

@@ -56,6 +56,11 @@ Changes to the LLVM IR
 * The ``nofpclass`` attribute was introduced. This allows more
   optimizations around special floating point value comparisons.
 
+* The constant expression variants of the following instructions have been
+  removed:
+
+  * ``select``
+
 Changes to building LLVM
 ------------------------
 
@@ -151,6 +156,12 @@ Changes to the C API
   These belonged to the no longer supported legacy pass manager.
 * As part of the opaque pointer transition, ``LLVMGetElementType`` no longer
   gives the pointee type of a pointer type.
+* The following functions for creating constant expressions have been removed,
+  because the underlying constant expressions are no longer supported. Instead,
+  an instruction should be created using the ``LLVMBuildXYZ`` APIs, which will
+  constant fold the operands if possible and create an instruction otherwise:
+
+  * ``LLVMConstSelect``
 
 Changes to the FastISel infrastructure
 --------------------------------------

llvm/include/llvm-c/Core.h

@@ -2257,9 +2257,6 @@ LLVMValueRef LLVMConstPointerCast(LLVMValueRef ConstantVal,
 LLVMValueRef LLVMConstIntCast(LLVMValueRef ConstantVal, LLVMTypeRef ToType,
                               LLVMBool isSigned);
 LLVMValueRef LLVMConstFPCast(LLVMValueRef ConstantVal, LLVMTypeRef ToType);
-LLVMValueRef LLVMConstSelect(LLVMValueRef ConstantCondition,
-                             LLVMValueRef ConstantIfTrue,
-                             LLVMValueRef ConstantIfFalse);
 LLVMValueRef LLVMConstExtractElement(LLVMValueRef VectorConstant,
                                      LLVMValueRef IndexConstant);
 LLVMValueRef LLVMConstInsertElement(LLVMValueRef VectorConstant,

llvm/include/llvm/IR/Constants.h

@@ -1208,12 +1208,6 @@ class ConstantExpr : public Constant {
   /// Return true if this is a compare constant expression
   bool isCompare() const;
 
-  /// Select constant expr
-  ///
-  /// \param OnlyIfReducedTy see \a getWithOperands() docs.
-  static Constant *getSelect(Constant *C, Constant *V1, Constant *V2,
-                             Type *OnlyIfReducedTy = nullptr);
-
   /// get - Return a binary or shift operator constant expression,
   /// folding if possible.
   ///

llvm/lib/AsmParser/LLParser.cpp

@@ -3882,6 +3882,8 @@ bool LLParser::parseValID(ValID &ID, PerFunctionState *PFS, Type *ExpectedTy) {
     return error(ID.Loc, "frem constexprs are no longer supported");
   case lltok::kw_fneg:
     return error(ID.Loc, "fneg constexprs are no longer supported");
+  case lltok::kw_select:
+    return error(ID.Loc, "select constexprs are no longer supported");
   case lltok::kw_icmp:
   case lltok::kw_fcmp: {
     unsigned PredVal, Opc = Lex.getUIntVal();
@@ -4011,8 +4013,7 @@ bool LLParser::parseValID(ValID &ID, PerFunctionState *PFS, Type *ExpectedTy) {
   case lltok::kw_getelementptr:
   case lltok::kw_shufflevector:
   case lltok::kw_insertelement:
-  case lltok::kw_extractelement:
-  case lltok::kw_select: {
+  case lltok::kw_extractelement: {
     unsigned Opc = Lex.getUIntVal();
     SmallVector<Constant*, 16> Elts;
     bool InBounds = false;
@@ -4091,13 +4092,6 @@ bool LLParser::parseValID(ValID &ID, PerFunctionState *PFS, Type *ExpectedTy) {
 
       ID.ConstantVal = ConstantExpr::getGetElementPtr(Ty, Elts[0], Indices,
                                                       InBounds, InRangeOp);
-    } else if (Opc == Instruction::Select) {
-      if (Elts.size() != 3)
-        return error(ID.Loc, "expected three operands to select");
-      if (const char *Reason = SelectInst::areInvalidOperands(Elts[0], Elts[1],
-                                                              Elts[2]))
-        return error(ID.Loc, Reason);
-      ID.ConstantVal = ConstantExpr::getSelect(Elts[0], Elts[1], Elts[2]);
     } else if (Opc == Instruction::ShuffleVector) {
       if (Elts.size() != 3)
         return error(ID.Loc, "expected three operands to shufflevector");

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -1417,7 +1417,13 @@ static bool isConstExprSupported(const BitcodeConstant *BC) {
   if (Opcode == Instruction::GetElementPtr)
     return ConstantExpr::isSupportedGetElementPtr(BC->SrcElemTy);
 
-  return Opcode != Instruction::FNeg;
+  switch (Opcode) {
+  case Instruction::FNeg:
+  case Instruction::Select:
+    return false;
+  default:
+    return true;
+  }
 }
 
 Expected<Value *> BitcodeReader::materializeValue(unsigned StartValID,
@@ -1549,9 +1555,6 @@ Expected<Value *> BitcodeReader::materializeValue(unsigned StartValID,
                                              ArrayRef(ConstOps).drop_front(),
                                              BC->Flags, BC->getInRangeIndex());
           break;
-        case Instruction::Select:
-          C = ConstantExpr::getSelect(ConstOps[0], ConstOps[1], ConstOps[2]);
-          break;
         case Instruction::ExtractElement:
           C = ConstantExpr::getExtractElement(ConstOps[0], ConstOps[1]);
           break;

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -2676,12 +2676,6 @@ void ModuleBitcodeWriter::writeConstants(unsigned FirstVal, unsigned LastVal,
         }
         break;
       }
-      case Instruction::Select:
-        Code = bitc::CST_CODE_CE_SELECT;
-        Record.push_back(VE.getValueID(C->getOperand(0)));
-        Record.push_back(VE.getValueID(C->getOperand(1)));
-        Record.push_back(VE.getValueID(C->getOperand(2)));
-        break;
       case Instruction::ExtractElement:
         Code = bitc::CST_CODE_CE_EXTRACTELT;
         Record.push_back(VE.getTypeID(C->getOperand(0)->getType()));

llvm/lib/IR/ConstantFold.cpp

@@ -593,17 +593,6 @@ Constant *llvm::ConstantFoldSelectInstruction(Constant *Cond,
   if (isa<UndefValue>(V1) && NotPoison(V2)) return V2;
   if (isa<UndefValue>(V2) && NotPoison(V1)) return V1;
 
-  if (ConstantExpr *TrueVal = dyn_cast<ConstantExpr>(V1)) {
-    if (TrueVal->getOpcode() == Instruction::Select)
-      if (TrueVal->getOperand(0) == Cond)
-        return ConstantExpr::getSelect(Cond, TrueVal->getOperand(1), V2);
-  }
-  if (ConstantExpr *FalseVal = dyn_cast<ConstantExpr>(V2)) {
-    if (FalseVal->getOpcode() == Instruction::Select)
-      if (FalseVal->getOperand(0) == Cond)
-        return ConstantExpr::getSelect(Cond, V1, FalseVal->getOperand(2));
-  }
-
   return nullptr;
 }
 

llvm/lib/IR/Constants.cpp

@@ -547,8 +547,6 @@ void llvm::deleteConstant(Constant *C) {
       delete static_cast<CastConstantExpr *>(C);
     else if (isa<BinaryConstantExpr>(C))
       delete static_cast<BinaryConstantExpr *>(C);
-    else if (isa<SelectConstantExpr>(C))
-      delete static_cast<SelectConstantExpr *>(C);
     else if (isa<ExtractElementConstantExpr>(C))
       delete static_cast<ExtractElementConstantExpr *>(C);
     else if (isa<InsertElementConstantExpr>(C))
@@ -1488,8 +1486,6 @@ Constant *ConstantExpr::getWithOperands(ArrayRef<Constant *> Ops, Type *Ty,
   case Instruction::BitCast:
   case Instruction::AddrSpaceCast:
     return ConstantExpr::getCast(getOpcode(), Ops[0], Ty, OnlyIfReduced);
-  case Instruction::Select:
-    return ConstantExpr::getSelect(Ops[0], Ops[1], Ops[2], OnlyIfReducedTy);
   case Instruction::InsertElement:
     return ConstantExpr::getInsertElement(Ops[0], Ops[1], Ops[2],
                                           OnlyIfReducedTy);
@@ -2441,23 +2437,6 @@ Constant *ConstantExpr::getCompare(unsigned short Predicate, Constant *C1,
   }
 }
 
-Constant *ConstantExpr::getSelect(Constant *C, Constant *V1, Constant *V2,
-                                  Type *OnlyIfReducedTy) {
-  assert(!SelectInst::areInvalidOperands(C, V1, V2)&&"Invalid select operands");
-
-  if (Constant *SC = ConstantFoldSelectInstruction(C, V1, V2))
-    return SC;        // Fold common cases
-
-  if (OnlyIfReducedTy == V1->getType())
-    return nullptr;
-
-  Constant *ArgVec[] = { C, V1, V2 };
-  ConstantExprKeyType Key(Instruction::Select, ArgVec);
-
-  LLVMContextImpl *pImpl = C->getContext().pImpl;
-  return pImpl->ExprConstants.getOrCreate(V1->getType(), Key);
-}
-
 Constant *ConstantExpr::getGetElementPtr(Type *Ty, Constant *C,
                                          ArrayRef<Value *> Idxs, bool InBounds,
                                          std::optional<unsigned> InRangeIndex,
@@ -3439,8 +3418,6 @@ Instruction *ConstantExpr::getAsInstruction(Instruction *InsertBefore) const {
   case Instruction::AddrSpaceCast:
     return CastInst::Create((Instruction::CastOps)getOpcode(), Ops[0],
                             getType(), "", InsertBefore);
-  case Instruction::Select:
-    return SelectInst::Create(Ops[0], Ops[1], Ops[2], "", InsertBefore);
   case Instruction::InsertElement:
     return InsertElementInst::Create(Ops[0], Ops[1], Ops[2], "", InsertBefore);
   case Instruction::ExtractElement:

llvm/lib/IR/ConstantsContext.h

@@ -90,32 +90,6 @@ class BinaryConstantExpr final : public ConstantExpr {
   }
 };
 
-/// SelectConstantExpr - This class is private to Constants.cpp, and is used
-/// behind the scenes to implement select constant exprs.
-class SelectConstantExpr final : public ConstantExpr {
-public:
-  SelectConstantExpr(Constant *C1, Constant *C2, Constant *C3)
-    : ConstantExpr(C2->getType(), Instruction::Select, &Op<0>(), 3) {
-    Op<0>() = C1;
-    Op<1>() = C2;
-    Op<2>() = C3;
-  }
-
-  // allocate space for exactly three operands
-  void *operator new(size_t S) { return User::operator new(S, 3); }
-  void operator delete(void *Ptr) { User::operator delete(Ptr); }
-
-  /// Transparently provide more efficient getOperand methods.
-  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Value);
-
-  static bool classof(const ConstantExpr *CE) {
-    return CE->getOpcode() == Instruction::Select;
-  }
-  static bool classof(const Value *V) {
-    return isa<ConstantExpr>(V) && classof(cast<ConstantExpr>(V));
-  }
-};
-
 /// ExtractElementConstantExpr - This class is private to
 /// Constants.cpp, and is used behind the scenes to implement
 /// extractelement constant exprs.
@@ -279,11 +253,6 @@ struct OperandTraits<BinaryConstantExpr>
     : public FixedNumOperandTraits<BinaryConstantExpr, 2> {};
 DEFINE_TRANSPARENT_OPERAND_ACCESSORS(BinaryConstantExpr, Value)
 
-template <>
-struct OperandTraits<SelectConstantExpr>
-    : public FixedNumOperandTraits<SelectConstantExpr, 3> {};
-DEFINE_TRANSPARENT_OPERAND_ACCESSORS(SelectConstantExpr, Value)
-
 template <>
 struct OperandTraits<ExtractElementConstantExpr>
     : public FixedNumOperandTraits<ExtractElementConstantExpr, 2> {};
@@ -523,8 +492,6 @@ struct ConstantExprKeyType {
         return new BinaryConstantExpr(Opcode, Ops[0], Ops[1],
                                       SubclassOptionalData);
       llvm_unreachable("Invalid ConstantExpr!");
-    case Instruction::Select:
-      return new SelectConstantExpr(Ops[0], Ops[1], Ops[2]);
     case Instruction::ExtractElement:
       return new ExtractElementConstantExpr(Ops[0], Ops[1]);
     case Instruction::InsertElement:

llvm/lib/IR/Core.cpp

@@ -1799,14 +1799,6 @@ LLVMValueRef LLVMConstFPCast(LLVMValueRef ConstantVal, LLVMTypeRef ToType) {
                                       unwrap(ToType)));
 }
 
-LLVMValueRef LLVMConstSelect(LLVMValueRef ConstantCondition,
-                             LLVMValueRef ConstantIfTrue,
-                             LLVMValueRef ConstantIfFalse) {
-  return wrap(ConstantExpr::getSelect(unwrap<Constant>(ConstantCondition),
-                                      unwrap<Constant>(ConstantIfTrue),
-                                      unwrap<Constant>(ConstantIfFalse)));
-}
-
 LLVMValueRef LLVMConstExtractElement(LLVMValueRef VectorConstant,
                                      LLVMValueRef IndexConstant) {
   return wrap(ConstantExpr::getExtractElement(unwrap<Constant>(VectorConstant),

llvm/lib/Transforms/Scalar/InferAddressSpaces.cpp

@@ -694,18 +694,6 @@ static Value *cloneConstantExprWithNewAddressSpace(
     return ConstantExpr::getAddrSpaceCast(CE, TargetType);
   }
 
-  if (CE->getOpcode() == Instruction::Select) {
-    Constant *Src0 = CE->getOperand(1);
-    Constant *Src1 = CE->getOperand(2);
-    if (Src0->getType()->getPointerAddressSpace() ==
-        Src1->getType()->getPointerAddressSpace()) {
-
-      return ConstantExpr::getSelect(
-          CE->getOperand(0), ConstantExpr::getAddrSpaceCast(Src0, TargetType),
-          ConstantExpr::getAddrSpaceCast(Src1, TargetType));
-    }
-  }
-
   if (CE->getOpcode() == Instruction::IntToPtr) {
     assert(isNoopPtrIntCastPair(cast<Operator>(CE), *DL, TTI));
     Constant *Src = cast<ConstantExpr>(CE->getOperand(0))->getOperand(0);

llvm/test/Analysis/ScalarEvolution/logical-operations.ll

@@ -410,11 +410,14 @@ define ptr @select_between_constantptrs(i1 %c, ptr %x) {
 define ptr @tautological_select() {
 ; CHECK-LABEL: 'tautological_select'
 ; CHECK-NEXT:  Classifying expressions for: @tautological_select
-; CHECK-NEXT:    %r = getelementptr i8, ptr @constant, i32 0
+; CHECK-NEXT:    %s = select i1 true, ptr @constant, ptr @another_constant
+; CHECK-NEXT:    --> @constant U: [0,-3) S: [-9223372036854775808,9223372036854775805)
+; CHECK-NEXT:    %r = getelementptr i8, ptr %s
 ; CHECK-NEXT:    --> @constant U: [0,-3) S: [-9223372036854775808,9223372036854775805)
 ; CHECK-NEXT:  Determining loop execution counts for: @tautological_select
 ;
-  %r = getelementptr i8, ptr select (i1 true, ptr @constant, ptr @another_constant), i32 0
+  %s = select i1 true, ptr @constant, ptr @another_constant
+  %r = getelementptr i8, ptr %s
   ret ptr %r
 }
 

llvm/test/Assembler/ConstantExprFoldSelect.ll

@@ -1,9 +1,9 @@
-; RUN: llvm-as < %s | llvm-dis | FileCheck %s
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
 ; RUN: verify-uselistorder %s
 ; PR18319
 
-define void @function() {
-  %c = trunc <4 x i16> select (<4 x i1> <i1 undef, i1 undef, i1 false, i1 true>, <4 x i16> <i16 undef, i16 2, i16 3, i16 4>, <4 x i16> <i16 -1, i16 -2, i16 -3, i16 -4>) to <4 x i8>
+define <4 x i16> @function() {
+  %s = select <4 x i1> <i1 undef, i1 undef, i1 false, i1 true>, <4 x i16> <i16 undef, i16 2, i16 3, i16 4>, <4 x i16> <i16 -1, i16 -2, i16 -3, i16 -4>
 ; CHECK: <i16 undef, i16 -2, i16 -3, i16 4>
-  ret void
+  ret <4 x i16> %s
 }

llvm/test/Bindings/OCaml/core.ml

@@ -333,18 +333,13 @@ let test_constants () =
   group "misc constants";
   (* CHECK: const_size_of{{.*}}getelementptr{{.*}}null
    * CHECK: const_gep{{.*}}getelementptr
-   * CHECK: const_select{{.*}}select
    * CHECK: const_extractelement{{.*}}extractelement
    * CHECK: const_insertelement{{.*}}insertelement
    * CHECK: const_shufflevector = global <4 x i32> <i32 0, i32 1, i32 1, i32 0>
    *)
   ignore (define_global "const_size_of" (size_of (pointer_type context)) m);
   ignore (define_global "const_gep" (const_gep i8_type foldbomb_gv [| five |])
           m);
-  ignore (define_global "const_select" (const_select
-    (const_icmp Icmp.Sle foldbomb five)
-    (const_int i8_type (-1))
-    (const_int i8_type 0)) m);
   let zero = const_int i32_type 0 in
   let one  = const_int i32_type 1 in
   ignore (define_global "const_extractelement" (const_extractelement

llvm/test/Bitcode/thinlto-function-summary-callgraph-cast.ll

@@ -9,7 +9,7 @@
 ; "op7" is a call to "callee" function.
 ; CHECK-NEXT:    <PERMODULE {{.*}} op7=3 op8=[[ALIASID:[0-9]+]]/>
 ; "another_caller" has only references but no calls.
-; CHECK-NEXT:    <PERMODULE {{.*}} op4=3 {{.*}} op9={{[0-9]+}}/>
+; CHECK-NEXT:    <PERMODULE {{.*}}/>
 ; CHECK-NEXT:    <PERMODULE {{.*}} op0=[[ALIASEEID:[0-9]+]]
 ; CHECK-NEXT:    <ALIAS {{.*}} op0=[[ALIASID]] {{.*}} op2=[[ALIASEEID]]/>
 ; CHECK-NEXT:    <BLOCK_COUNT op0=3/>
@@ -27,7 +27,7 @@ define void @caller() {
 
 define void @another_caller() {
     ; Test calls that aren't handled either as direct or indirect.
-    call void select (i1 icmp eq (ptr @global, ptr null), ptr @f, ptr @g)()
+    call void getelementptr (i8, ptr @f, i64 ptrtoint (ptr @g to i64))()
     ret void
 }