[SVE ACLE] Allow default zero initialisation for svcount_t. (#69321)

This matches the behaviour of the other SVE ACLE types.

Author: paulwalker-arm

clang/test/CodeGenCXX/aarch64-sve-vector-init.cpp

@@ -55,6 +55,7 @@
 // CHECK-NEXT:    [[B8:%.*]] = alloca <vscale x 16 x i1>, align 2
 // CHECK-NEXT:    [[B8X2:%.*]] = alloca <vscale x 32 x i1>, align 2
 // CHECK-NEXT:    [[B8X4:%.*]] = alloca <vscale x 64 x i1>, align 2
+// CHECK-NEXT:    [[CNT:%.*]] = alloca target("aarch64.svcount"), align 2
 // CHECK-NEXT:    store <vscale x 16 x i8> zeroinitializer, ptr [[S8]], align 16
 // CHECK-NEXT:    store <vscale x 8 x i16> zeroinitializer, ptr [[S16]], align 16
 // CHECK-NEXT:    store <vscale x 4 x i32> zeroinitializer, ptr [[S32]], align 16
@@ -106,6 +107,7 @@
 // CHECK-NEXT:    store <vscale x 16 x i1> zeroinitializer, ptr [[B8]], align 2
 // CHECK-NEXT:    store <vscale x 32 x i1> zeroinitializer, ptr [[B8X2]], align 2
 // CHECK-NEXT:    store <vscale x 64 x i1> zeroinitializer, ptr [[B8X4]], align 2
+// CHECK-NEXT:    store target("aarch64.svcount") zeroinitializer, ptr [[CNT]], align 2
 // CHECK-NEXT:    ret void
 //
 void test_locals(void) {
@@ -164,6 +166,8 @@ void test_locals(void) {
   __SVBool_t b8{};
   __clang_svboolx2_t b8x2{};
   __clang_svboolx4_t b8x4{};
+
+  __SVCount_t cnt{};
 }
 
 // CHECK-LABEL: define dso_local void @_Z12test_copy_s8u10__SVInt8_t
@@ -879,3 +883,17 @@ void test_copy_b8x2(__clang_svboolx2_t a) {
 void test_copy_b8x4(__clang_svboolx4_t a) {
   __clang_svboolx4_t b{a};
 }
+
+// CHECK-LABEL: define dso_local void @_Z13test_copy_cntu11__SVCount_t
+// CHECK-SAME: (target("aarch64.svcount") [[A:%.*]]) #[[ATTR0]] {
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca target("aarch64.svcount"), align 2
+// CHECK-NEXT:    [[B:%.*]] = alloca target("aarch64.svcount"), align 2
+// CHECK-NEXT:    store target("aarch64.svcount") [[A]], ptr [[A_ADDR]], align 2
+// CHECK-NEXT:    [[TMP0:%.*]] = load target("aarch64.svcount"), ptr [[A_ADDR]], align 2
+// CHECK-NEXT:    store target("aarch64.svcount") [[TMP0]], ptr [[B]], align 2
+// CHECK-NEXT:    ret void
+//
+void test_copy_cnt(__SVCount_t a) {
+  __SVCount_t b{a};
+}

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -1738,6 +1738,12 @@ SDValue SelectionDAGBuilder::getValueImpl(const Value *V) {
     if (const auto *NC = dyn_cast<NoCFIValue>(C))
       return getValue(NC->getGlobalValue());
 
+    if (VT == MVT::aarch64svcount) {
+      assert(C->isNullValue() && "Can only zero this target type!");
+      return DAG.getNode(ISD::BITCAST, getCurSDLoc(), VT,
+                         DAG.getConstant(0, getCurSDLoc(), MVT::nxv16i1));
+    }
+
     VectorType *VecTy = cast<VectorType>(V->getType());
 
     // Now that we know the number and type of the elements, get that number of

llvm/lib/IR/Type.cpp

@@ -841,7 +841,8 @@ static TargetTypeInfo getTargetTypeInfo(const TargetExtType *Ty) {
 
   // Opaque types in the AArch64 name space.
   if (Name == "aarch64.svcount")
-    return TargetTypeInfo(ScalableVectorType::get(Type::getInt1Ty(C), 16));
+    return TargetTypeInfo(ScalableVectorType::get(Type::getInt1Ty(C), 16),
+                          TargetExtType::HasZeroInit);
 
   return TargetTypeInfo(Type::getVoidTy(C));
 }

llvm/test/CodeGen/AArch64/sve-zeroinit.ll

@@ -86,3 +86,10 @@ define <vscale x 16 x i1> @test_zeroinit_16xi1() {
 ; CHECK-NEXT:  ret
   ret <vscale x 16 x i1> zeroinitializer
 }
+
+define target("aarch64.svcount") @test_zeroinit_svcount() "target-features"="+sme2" {
+; CHECK-LABEL: test_zeroinit_svcount
+; CHECK:       pfalse p0.b
+; CHECK-NEXT:  ret
+  ret target("aarch64.svcount") zeroinitializer
+}