[SYCL] Enable sub group masks for 64 bit subgroups (#7491)

This patch is adding group ballot support for HIP (based on initial work
from @abagusetty on #6734 ), but also
extending the sub-group mask implementation to support 64 bit masks, as
a lot of AMD GPUs use 64 bit wavefronts.

Related to issue: #6718

libclc/amdgcn-amdhsa/libspirv/SOURCES

@@ -1,5 +1,6 @@
 
 workitem/get_global_offset.ll
+group/group_ballot.cl
 group/collectives.cl
 group/collectives_helpers.ll
 atomic/loadstore_helpers.ll

libclc/amdgcn-amdhsa/libspirv/group/group_ballot.cl

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <spirv/spirv.h>
+#include <spirv/spirv_types.h>
+
+// from llvm/include/llvm/IR/InstrTypes.h
+#define ICMP_NE 33
+
+_CLC_DEF _CLC_CONVERGENT __clc_vec4_uint32_t
+_Z29__spirv_GroupNonUniformBallotjb(unsigned flag, bool predicate) {
+  // only support subgroup for now
+  if (flag != Subgroup) {
+    __builtin_trap();
+    __builtin_unreachable();
+  }
+
+  // prepare result, we only support the ballot operation on 64 threads maximum
+  // so we only need the first two elements to represent the final mask
+  __clc_vec4_uint32_t res;
+  res[2] = 0;
+  res[3] = 0;
+
+  // run the ballot operation
+  res.xy = __builtin_amdgcn_uicmp((int)predicate, 0, ICMP_NE);
+
+  return res;
+}

sycl/include/sycl/detail/helpers.hpp

@@ -82,8 +82,8 @@ class Builder {
     return group<Dims>(Global, Local, Global / Local, Index);
   }
 
-  template <class ResType>
-  static ResType createSubGroupMask(uint32_t Bits, size_t BitsNum) {
+  template <class ResType, typename BitsType>
+  static ResType createSubGroupMask(BitsType Bits, size_t BitsNum) {
     return ResType(Bits, BitsNum);
   }
 

sycl/include/sycl/ext/oneapi/sub_group_mask.hpp

@@ -23,9 +23,19 @@ class Builder;
 namespace ext {
 namespace oneapi {
 
+#if defined(__SYCL_DEVICE_ONLY__) && defined(__AMDGCN__) &&                    \
+    (__AMDGCN_WAVEFRONT_SIZE == 64)
+#define BITS_TYPE uint64_t
+#else
+#define BITS_TYPE uint32_t
+#endif
+
 struct sub_group_mask {
   friend class detail::Builder;
-  static constexpr size_t max_bits = 32 /* implementation-defined */;
+  using BitsType = BITS_TYPE;
+
+  static constexpr size_t max_bits =
+      sizeof(BitsType) * CHAR_BIT /* implementation-defined */;
   static constexpr size_t word_size = sizeof(uint32_t) * CHAR_BIT;
 
   // enable reference to individual bit
@@ -55,9 +65,9 @@ struct sub_group_mask {
 
   private:
     // Reference to the word containing the bit
-    uint32_t &Ref;
+    BitsType &Ref;
     // Bit mask where only referenced bit is set
-    uint32_t RefBit;
+    BitsType RefBit;
   };
 
   bool operator[](id<1> id) const {
@@ -96,9 +106,9 @@ struct sub_group_mask {
             typename = sycl::detail::enable_if_t<std::is_integral<Type>::value>>
   void insert_bits(Type bits, id<1> pos = 0) {
     size_t insert_size = sizeof(Type) * CHAR_BIT;
-    uint32_t insert_data = (uint32_t)bits;
+    BitsType insert_data = (BitsType)bits;
     insert_data <<= pos.get(0);
-    uint32_t mask = 0;
+    BitsType mask = 0;
     if (pos.get(0) + insert_size < size())
       mask |= (valuable_bits(bits_num) << (pos.get(0) + insert_size));
     if (pos.get(0) < size() && pos.get(0))
@@ -108,8 +118,8 @@ struct sub_group_mask {
   }
 
   /* The bits are stored in the memory in the following way:
-  marray id |     0     |     1     |     2     |     3     |
-  bit id    |7   ..    0|15   ..   8|23   ..  16|31  ..   24|
+  marray id |     0     |     1     |     2     |     3     |...
+  bit id    |7   ..    0|15   ..   8|23   ..  16|31  ..   24|...
   */
   template <typename Type, size_t Size,
             typename = sycl::detail::enable_if_t<std::is_integral<Type>::value>>
@@ -158,7 +168,7 @@ struct sub_group_mask {
 
   void set() { Bits = valuable_bits(bits_num); }
   void set(id<1> id, bool value = true) { operator[](id) = value; }
-  void reset() { Bits = uint32_t{0}; }
+  void reset() { Bits = BitsType{0}; }
   void reset(id<1> id) { operator[](id) = 0; }
   void reset_low() { reset(find_low()); }
   void reset_high() { reset(find_high()); }
@@ -240,13 +250,17 @@ struct sub_group_mask {
   }
 
 private:
-  sub_group_mask(uint32_t rhs, size_t bn) : Bits(rhs), bits_num(bn) {
+  sub_group_mask(BitsType rhs, size_t bn) : Bits(rhs), bits_num(bn) {
     assert(bits_num <= max_bits);
   }
-  inline uint32_t valuable_bits(size_t bn) const {
-    return static_cast<uint32_t>((1ULL << bn) - 1ULL);
+  inline BitsType valuable_bits(size_t bn) const {
+    assert(bn <= max_bits);
+    BitsType one = 1;
+    if (bn == max_bits)
+      return -one;
+    return (one << bn) - one;
   }
-  uint32_t Bits;
+  BitsType Bits;
   // Number of valuable bits
   size_t bits_num;
 };
@@ -259,15 +273,20 @@ group_ballot(Group g, bool predicate) {
 #ifdef __SYCL_DEVICE_ONLY__
   auto res = __spirv_GroupNonUniformBallot(
       detail::spirv::group_scope<Group>::value, predicate);
+  BITS_TYPE val = res[0];
+  if constexpr (sizeof(BITS_TYPE) == 8)
+    val |= ((BITS_TYPE)res[1]) << 32;
   return detail::Builder::createSubGroupMask<sub_group_mask>(
-      res[0], g.get_max_local_range()[0]);
+      val, g.get_max_local_range()[0]);
 #else
   (void)predicate;
   throw exception{errc::feature_not_supported,
                   "Sub-group mask is not supported on host device"};
 #endif
 }
 
+#undef BITS_TYPE
+
 } // namespace oneapi
 } // namespace ext
 } // __SYCL_INLINE_VER_NAMESPACE(_V1)