Revert "[DirectX] Add atan2 intrinsic and expand for DXIL backend (p1…

…)" (llvm#109842)

Reverts llvm#108865

Broke the Docs build

llvm/docs/LangRef.rst

@@ -15583,43 +15583,6 @@ trapping or setting ``errno``.
 When specified with the fast-math-flag 'afn', the result may be approximated
 using a less accurate calculation.
 
-'``llvm.atan2.*``' Intrinsic
-^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-Syntax:
-"""""""
-
-This is an overloaded intrinsic. You can use ``llvm.atan2`` on any
-floating-point or vector of floating-point type. Not all targets support
-all types however.
-
-::
-
-      declare float     @llvm.atan2.f32(float  %X, float %Y)
-      declare double    @llvm.atan2.f64(double %X, double %Y)
-      declare x86_fp80  @llvm.atan2.f80(x86_fp80  %X, x86_fp80 %Y)
-      declare fp128     @llvm.atan2.f128(fp128 %X, fp128 %Y)
-      declare ppc_fp128 @llvm.atan2.ppcf128(ppc_fp128  %X, ppc_fp128 %Y)
-
-Overview:
-"""""""""
-
-The '``llvm.atan2.*``' intrinsics return the arctangent of the operand.
-
-Arguments:
-""""""""""
-
-The arguments and return value are floating-point numbers of the same type.
-
-Semantics:
-""""""""""
-
-Return the same value as a corresponding libm '``atan2``' function but without
-trapping or setting ``errno``.
-
-When specified with the fast-math-flag 'afn', the result may be approximated
-using a less accurate calculation.
-
 '``llvm.sinh.*``' Intrinsic
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 

llvm/include/llvm/IR/Intrinsics.td

@@ -1016,7 +1016,6 @@ let IntrProperties = [IntrNoMem, IntrSpeculatable, IntrWillReturn] in {
   def int_asin : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;
   def int_acos : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;
   def int_atan : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;
-  def int_atan2 : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>, LLVMMatchType<0>]>;
   def int_sin  : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;
   def int_cos  : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;
   def int_tan  : DefaultAttrsIntrinsic<[llvm_anyfloat_ty], [LLVMMatchType<0>]>;

llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp

@@ -36,7 +36,6 @@ using namespace llvm;
 static bool isIntrinsicExpansion(Function &F) {
   switch (F.getIntrinsicID()) {
   case Intrinsic::abs:
-  case Intrinsic::atan2:
   case Intrinsic::exp:
   case Intrinsic::log:
   case Intrinsic::log10:
@@ -308,54 +307,6 @@ static Value *expandNormalizeIntrinsic(CallInst *Orig) {
   return Builder.CreateFMul(X, MultiplicandVec);
 }
 
-static Value *expandAtan2Intrinsic(CallInst *Orig) {
-  Value *Y = Orig->getOperand(0);
-  Value *X = Orig->getOperand(1);
-  Type *Ty = X->getType();
-  IRBuilder<> Builder(Orig);
-  Builder.setFastMathFlags(Orig->getFastMathFlags());
-
-  Value *Tan = Builder.CreateFDiv(Y, X);
-
-  CallInst *Atan =
-      Builder.CreateIntrinsic(Ty, Intrinsic::atan, {Tan}, nullptr, "Elt.Atan");
-  Atan->setTailCall(Orig->isTailCall());
-  Atan->setAttributes(Orig->getAttributes());
-
-  // Modify atan result based on https://en.wikipedia.org/wiki/Atan2.
-  Constant *Pi = ConstantFP::get(Ty, llvm::numbers::pi);
-  Constant *HalfPi = ConstantFP::get(Ty, llvm::numbers::pi / 2);
-  Constant *NegHalfPi = ConstantFP::get(Ty, -llvm::numbers::pi / 2);
-  Constant *Zero = ConstantFP::get(Ty, 0);
-  Value *AtanAddPi = Builder.CreateFAdd(Atan, Pi);
-  Value *AtanSubPi = Builder.CreateFSub(Atan, Pi);
-
-  // x > 0 -> atan.
-  Value *Result = Atan;
-  Value *XLt0 = Builder.CreateFCmpOLT(X, Zero);
-  Value *XEq0 = Builder.CreateFCmpOEQ(X, Zero);
-  Value *YGe0 = Builder.CreateFCmpOGE(Y, Zero);
-  Value *YLt0 = Builder.CreateFCmpOLT(Y, Zero);
-
-  // x < 0, y >= 0 -> atan + pi.
-  Value *XLt0AndYGe0 = Builder.CreateAnd(XLt0, YGe0);
-  Result = Builder.CreateSelect(XLt0AndYGe0, AtanAddPi, Result);
-
-  // x < 0, y < 0 -> atan - pi.
-  Value *XLt0AndYLt0 = Builder.CreateAnd(XLt0, YLt0);
-  Result = Builder.CreateSelect(XLt0AndYLt0, AtanSubPi, Result);
-
-  // x == 0, y < 0 -> -pi/2
-  Value *XEq0AndYLt0 = Builder.CreateAnd(XEq0, YLt0);
-  Result = Builder.CreateSelect(XEq0AndYLt0, NegHalfPi, Result);
-
-  // x == 0, y > 0 -> pi/2
-  Value *XEq0AndYGe0 = Builder.CreateAnd(XEq0, YGe0);
-  Result = Builder.CreateSelect(XEq0AndYGe0, HalfPi, Result);
-
-  return Result;
-}
-
 static Value *expandPowIntrinsic(CallInst *Orig) {
 
   Value *X = Orig->getOperand(0);
@@ -467,9 +418,6 @@ static bool expandIntrinsic(Function &F, CallInst *Orig) {
   case Intrinsic::abs:
     Result = expandAbs(Orig);
     break;
-  case Intrinsic::atan2:
-    Result = expandAtan2Intrinsic(Orig);
-    break;
   case Intrinsic::exp:
     Result = expandExpIntrinsic(Orig);
     break;