[DXIL] Complete abs lowering (#86158)

This change completes #86155
- `DXIL.td` - lowering `fabs` intrinsic to the float dxil op.
- `DXILIntrinsicExpansion.cpp` - Add intrinsic expansion for the abs
case.

Author: farzonl

llvm/lib/Target/DirectX/DXIL.td

@@ -255,6 +255,8 @@ class DXILOpMapping<int opCode, DXILOpClass opClass,
 }
 
 // Concrete definition of DXIL Operation mapping to corresponding LLVM intrinsic
+def Abs : DXILOpMapping<6, unary, int_fabs,
+                         "Returns the absolute value of the input.">;
 def IsInf : DXILOpMapping<9, isSpecialFloat, int_dx_isinf,
                          "Determines if the specified value is infinite.",
                          [llvm_i1_ty, llvm_halforfloat_ty]>;

llvm/lib/Target/DirectX/DXILIntrinsicExpansion.cpp

@@ -33,6 +33,7 @@ using namespace llvm;
 
 static bool isIntrinsicExpansion(Function &F) {
   switch (F.getIntrinsicID()) {
+  case Intrinsic::abs:
   case Intrinsic::exp:
   case Intrinsic::dx_any:
   case Intrinsic::dx_clamp:
@@ -46,6 +47,26 @@ static bool isIntrinsicExpansion(Function &F) {
   return false;
 }
 
+static bool expandAbs(CallInst *Orig) {
+  Value *X = Orig->getOperand(0);
+  IRBuilder<> Builder(Orig->getParent());
+  Builder.SetInsertPoint(Orig);
+  Type *Ty = X->getType();
+  Type *EltTy = Ty->getScalarType();
+  Constant *Zero = Ty->isVectorTy()
+                       ? ConstantVector::getSplat(
+                             ElementCount::getFixed(
+                                 cast<FixedVectorType>(Ty)->getNumElements()),
+                             ConstantInt::get(EltTy, 0))
+                       : ConstantInt::get(EltTy, 0);
+  auto *V = Builder.CreateSub(Zero, X);
+  auto *MaxCall =
+      Builder.CreateIntrinsic(Ty, Intrinsic::smax, {X, V}, nullptr, "dx.max");
+  Orig->replaceAllUsesWith(MaxCall);
+  Orig->eraseFromParent();
+  return true;
+}
+
 static bool expandIntegerDot(CallInst *Orig, Intrinsic::ID DotIntrinsic) {
   assert(DotIntrinsic == Intrinsic::dx_sdot ||
          DotIntrinsic == Intrinsic::dx_udot);
@@ -213,6 +234,8 @@ static bool expandClampIntrinsic(CallInst *Orig, Intrinsic::ID ClampIntrinsic) {
 
 static bool expandIntrinsic(Function &F, CallInst *Orig) {
   switch (F.getIntrinsicID()) {
+  case Intrinsic::abs:
+    return expandAbs(Orig);
   case Intrinsic::exp:
     return expandExpIntrinsic(Orig);
   case Intrinsic::dx_any:

llvm/test/CodeGen/DirectX/abs-vec.ll

@@ -0,0 +1,34 @@
+; RUN: opt -S  -dxil-intrinsic-expansion  < %s | FileCheck %s 
+
+; Make sure dxil operation function calls for abs are generated for int vectors.
+
+; CHECK-LABEL: abs_i16Vec2
+define noundef <2 x i16> @abs_i16Vec2(<2 x i16> noundef %a) #0 {
+entry:
+; CHECK: sub <2 x i16> zeroinitializer, %a
+; CHECK: call <2 x i16> @llvm.smax.v2i16(<2 x i16> %a, <2 x i16> %{{.*}})
+  %elt.abs = call <2 x i16> @llvm.abs.v2i16(<2 x i16> %a, i1 false)
+  ret <2 x i16> %elt.abs
+}
+
+; CHECK-LABEL: abs_i32Vec3
+define noundef <3 x i32> @abs_i32Vec3(<3 x i32> noundef %a) #0 {
+entry:
+; CHECK: sub <3 x i32> zeroinitializer, %a
+; CHECK: call <3 x i32> @llvm.smax.v3i32(<3 x i32> %a, <3 x i32> %{{.*}})
+  %elt.abs = call <3 x i32> @llvm.abs.v3i32(<3 x i32> %a, i1 false)
+  ret <3 x i32> %elt.abs
+}
+
+; CHECK-LABEL: abs_i64Vec4
+define noundef <4 x i64> @abs_i64Vec4(<4 x i64> noundef %a) #0 {
+entry:
+; CHECK: sub <4 x i64> zeroinitializer, %a
+; CHECK: call <4 x i64> @llvm.smax.v4i64(<4 x i64> %a, <4 x i64> %{{.*}})
+  %elt.abs = call <4 x i64> @llvm.abs.v4i64(<4 x i64> %a, i1 false)
+  ret <4 x i64> %elt.abs
+}
+
+declare <2 x i16> @llvm.abs.v2i16(<2 x i16>, i1 immarg)
+declare <3 x i32> @llvm.abs.v3i32(<3 x i32>, i1 immarg)
+declare <4 x i64> @llvm.abs.v4i64(<4 x i64>, i1 immarg)

llvm/test/CodeGen/DirectX/abs.ll

@@ -0,0 +1,38 @@
+; RUN: opt -S  -dxil-intrinsic-expansion  < %s | FileCheck %s --check-prefixes=CHECK,EXPCHECK
+; RUN: opt -S  -dxil-op-lower  < %s | FileCheck %s --check-prefixes=CHECK,DOPCHECK
+
+; Make sure dxil operation function calls for abs are generated for int16_t/int/int64_t.
+
+; CHECK-LABEL: abs_i16
+define noundef i16 @abs_i16(i16 noundef %a) {
+entry:
+; CHECK: sub i16 0, %a
+; EXPCHECK: call i16 @llvm.smax.i16(i16 %a, i16 %{{.*}})
+; DOPCHECK: call i16 @dx.op.binary.i16(i32 37, i16 %a, i16 %{{.*}})
+  %elt.abs = call i16 @llvm.abs.i16(i16 %a, i1 false)
+  ret i16 %elt.abs
+}
+
+; CHECK-LABEL: abs_i32
+define noundef i32 @abs_i32(i32 noundef %a) {
+entry:
+; CHECK: sub i32 0, %a
+; EXPCHECK: call i32 @llvm.smax.i32(i32 %a, i32 %{{.*}})
+; DOPCHECK: call i32 @dx.op.binary.i32(i32 37, i32 %a, i32 %{{.*}})
+  %elt.abs = call i32 @llvm.abs.i32(i32 %a, i1 false)
+  ret i32 %elt.abs
+}
+
+; CHECK-LABEL: abs_i64
+define noundef i64 @abs_i64(i64 noundef %a) {
+entry:
+; CHECK: sub i64 0, %a
+; EXPCHECK: call i64 @llvm.smax.i64(i64 %a, i64 %{{.*}})
+; DOPCHECK: call i64 @dx.op.binary.i64(i32 37, i64 %a, i64 %{{.*}})
+  %elt.abs = call i64 @llvm.abs.i64(i64 %a, i1 false)
+  ret i64 %elt.abs
+}
+
+declare i16 @llvm.abs.i16(i16, i1 immarg)
+declare i32 @llvm.abs.i32(i32, i1 immarg)
+declare i64 @llvm.abs.i64(i64, i1 immarg)

llvm/test/CodeGen/DirectX/fabs.ll

@@ -0,0 +1,32 @@
+; RUN: opt -S -dxil-op-lower < %s | FileCheck %s
+
+; Make sure dxil operation function calls for abs are generated for float, half, and double.
+
+
+; CHECK-LABEL: fabs_half
+define noundef half @fabs_half(half noundef %a) {
+entry:
+  ; CHECK: call half @dx.op.unary.f16(i32 6, half %{{.*}})
+  %elt.abs = call half @llvm.fabs.f16(half %a)
+  ret half %elt.abs
+}
+
+; CHECK-LABEL: fabs_float
+define noundef float @fabs_float(float noundef %a) {
+entry:
+; CHECK: call float @dx.op.unary.f32(i32 6, float %{{.*}})
+  %elt.abs = call float @llvm.fabs.f32(float %a)
+  ret float %elt.abs
+}
+
+; CHECK-LABEL: fabs_double
+define noundef double @fabs_double(double noundef %a) {
+entry:
+; CHECK: call double @dx.op.unary.f64(i32 6, double %{{.*}})
+  %elt.abs = call double @llvm.fabs.f64(double %a)
+  ret double %elt.abs
+}
+
+declare half @llvm.fabs.f16(half)
+declare float @llvm.fabs.f32(float)
+declare double @llvm.fabs.f64(double)