[SYCL] Fix Ambiguity in Overloaded Unary Minus Operator for bfloat16 (#15393)

This commit resolves an overload resolution ambiguity on Windows
self-builds in downstream pulldown when using the unary minus operator
with bfloat16. The operator now takes a const-qualified argument,
enabling its use with both lvalues and rvalues and fixing the reported
build error.

---------

Signed-off-by: Larsen, Steffen <steffen.larsen@intel.com>
Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>
Signed-off-by: Soumi Manna <soumi.manna@intel.com>
Co-authored-by: Steffen Larsen <steffen.larsen@intel.com>
Co-authored-by: Fraser Cormack <fraser@codeplay.com>
Co-authored-by: Artur Gainullin <artur.gainullin@intel.com>
Co-authored-by: Nick Sarnie <sarnex@users.noreply.github.com>
Co-authored-by: Kenneth Benzie (Benie) <k.benzie@codeplay.com>
Co-authored-by: Chris Perkins <chris.perkins@intel.com>
Co-authored-by: Michael Toguchi <michael.d.toguchi@intel.com>

Author: 8 people

sycl/include/sycl/ext/oneapi/bfloat16.hpp

@@ -182,7 +182,7 @@ class bfloat16 {
   explicit operator bool() { return to_float(value) != 0.0f; }
 
   // Unary minus operator overloading
-  friend bfloat16 operator-(bfloat16 &lhs) {
+  friend bfloat16 operator-(const bfloat16 &lhs) {
 #if defined(__SYCL_DEVICE_ONLY__) && defined(__NVPTX__) &&                     \
     (__SYCL_CUDA_ARCH__ >= 800)
     detail::Bfloat16StorageT res;

sycl/test/check_device_code/vector/vector_math_ops.cpp

@@ -341,26 +341,26 @@ SYCL_EXTERNAL auto TestNegation(vec<ext::oneapi::bfloat16, 3> a) { return !a; }
 // CHECK-NEXT:    [[REF_TMP_I:%.*]] = alloca float, align 4
 // CHECK-NEXT:    [[A_ASCAST:%.*]] = addrspacecast ptr [[A]] to ptr addrspace(4)
 // CHECK-NEXT:    tail call void @llvm.experimental.noalias.scope.decl(metadata [[META100:![0-9]+]])
-// CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[REF_TMP_I]])
-// CHECK-NEXT:    [[REF_TMP_ASCAST_I:%.*]] = addrspacecast ptr [[REF_TMP_I]] to ptr addrspace(4)
 // CHECK-NEXT:    tail call void @llvm.memset.p4.i64(ptr addrspace(4) noundef align 32 dereferenceable(32) [[AGG_RESULT]], i8 0, i64 32, i1 false), !alias.scope [[META100]]
+// CHECK-NEXT:    [[REF_TMP_ASCAST_I:%.*]] = addrspacecast ptr [[REF_TMP_I]] to ptr addrspace(4)
 // CHECK-NEXT:    br label [[FOR_COND_I:%.*]]
 // CHECK:       for.cond.i:
 // CHECK-NEXT:    [[I_0_I:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INC_I:%.*]], [[FOR_BODY_I:%.*]] ]
 // CHECK-NEXT:    [[CMP_I:%.*]] = icmp ult i64 [[I_0_I]], 16
 // CHECK-NEXT:    br i1 [[CMP_I]], label [[FOR_BODY_I]], label [[_ZN4SYCL3_V16DETAILNGERKNS0_3VECINS0_3EXT6ONEAPI8BFLOAT16ELI16EEE_EXIT:%.*]]
 // CHECK:       for.body.i:
 // CHECK-NEXT:    [[ARRAYIDX_I_I_I_I:%.*]] = getelementptr inbounds [16 x %"class.sycl::_V1::ext::oneapi::bfloat16"], ptr addrspace(4) [[A_ASCAST]], i64 0, i64 [[I_0_I]]
-// CHECK-NEXT:    [[CALL_I_I_I:%.*]] = call spir_func noundef float @__devicelib_ConvertBF16ToFINTEL(ptr addrspace(4) noundef align 2 dereferenceable(2) [[ARRAYIDX_I_I_I_I]]) #[[ATTR8]], !noalias [[META100]]
+// CHECK-NEXT:    call void @llvm.lifetime.start.p0(i64 4, ptr nonnull [[REF_TMP_I]])
+// CHECK-NEXT:    [[CALL_I_I_I:%.*]] = call spir_func float @__devicelib_ConvertBF16ToFINTEL(ptr addrspace(4) noundef align 2 dereferenceable(2) [[ARRAYIDX_I_I_I_I]]) #[[ATTR8]], !noalias [[META103:![0-9]+]]
 // CHECK-NEXT:    [[FNEG_I:%.*]] = fneg float [[CALL_I_I_I]]
-// CHECK-NEXT:    store float [[FNEG_I]], ptr [[REF_TMP_I]], align 4, !tbaa [[TBAA47]], !noalias [[META100]]
+// CHECK-NEXT:    store float [[FNEG_I]], ptr [[REF_TMP_I]], align 4, !tbaa [[TBAA47]], !noalias [[META103]]
+// CHECK-NEXT:    [[CALL_I_I10_I:%.*]] = call spir_func noundef zeroext i16 @__devicelib_ConvertFToBF16INTEL(ptr addrspace(4) noundef align 4 dereferenceable(4) [[REF_TMP_ASCAST_I]]) #[[ATTR8]], !noalias [[META103]]
+// CHECK-NEXT:     call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[REF_TMP_I]])
 // CHECK-NEXT:    [[ARRAYIDX_I_I_I9_I:%.*]] = getelementptr inbounds [16 x %"class.sycl::_V1::ext::oneapi::bfloat16"], ptr addrspace(4) [[AGG_RESULT]], i64 0, i64 [[I_0_I]]
-// CHECK-NEXT:    [[CALL_I_I10_I:%.*]] = call spir_func noundef zeroext i16 @__devicelib_ConvertFToBF16INTEL(ptr addrspace(4) noundef align 4 dereferenceable(4) [[REF_TMP_ASCAST_I]]) #[[ATTR8]], !noalias [[META100]]
 // CHECK-NEXT:    store i16 [[CALL_I_I10_I]], ptr addrspace(4) [[ARRAYIDX_I_I_I9_I]], align 2, !tbaa [[TBAA103:![0-9]+]], !alias.scope [[META100]]
 // CHECK-NEXT:    [[INC_I]] = add nuw nsw i64 [[I_0_I]], 1
 // CHECK-NEXT:    br label [[FOR_COND_I]], !llvm.loop [[LOOP105:![0-9]+]]
 // CHECK:       _ZN4sycl3_V16detailngERKNS0_3vecINS0_3ext6oneapi8bfloat16ELi16EEE.exit:
-// CHECK-NEXT:    call void @llvm.lifetime.end.p0(i64 4, ptr nonnull [[REF_TMP_I]])
 // CHECK-NEXT:    ret void
 //
 SYCL_EXTERNAL auto TestMinus(vec<ext::oneapi::bfloat16, 16> a) { return -a; }