[RISCV] Implement Builtins for XAndesBFHCvt extension. (#148804)

XAndesBFHCvt provides two builtins functions for converting between
float and bf16. Users can use them to convert bf16 values loaded from
memory to float, perform arithmetic operations, then convert them back
to bf16 and store them to memory.

The load/store and move operations for bf16 will be handled in a later
patch.

Author: tclin914

clang/include/clang/Basic/BuiltinsRISCV.td

@@ -157,3 +157,8 @@ def pause : RISCVBuiltin<"void()">;
 // XCV extensions.
 //===----------------------------------------------------------------------===//
 include "clang/Basic/BuiltinsRISCVXCV.td"
+
+//===----------------------------------------------------------------------===//
+// XAndes extensions.
+//===----------------------------------------------------------------------===//
+include "clang/Basic/BuiltinsRISCVXAndes.td"

clang/include/clang/Basic/BuiltinsRISCVXAndes.td

@@ -0,0 +1,27 @@
+//==- BuiltinsRISCVXAndes.td - RISC-V Andes Builtin database -----*- C++ -*-==//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the Andes-specific builtin function database.  Users of
+// this file must define the BUILTIN macro to make use of this information.
+//
+//===----------------------------------------------------------------------===//
+
+class RISCVXAndesBuiltin<string prototype, string features = ""> : TargetBuiltin {
+  let Spellings = ["__builtin_riscv_nds_" # NAME];
+  let Prototype = prototype;
+  let Features = features;
+}
+
+let Attributes = [NoThrow, Const] in {
+//===----------------------------------------------------------------------===//
+// XAndesBFHCvt extension.
+//===----------------------------------------------------------------------===//
+
+def fcvt_s_bf16 : RISCVXAndesBuiltin<"float(__bf16)", "xandesbfhcvt">;
+def fcvt_bf16_s : RISCVXAndesBuiltin<"__bf16(float)", "xandesbfhcvt">;
+} // Attributes = [NoThrow, Const]

clang/lib/CodeGen/TargetBuiltins/RISCV.cpp

@@ -413,6 +413,12 @@ Value *CodeGenFunction::EmitRISCVBuiltinExpr(unsigned BuiltinID,
     ID = Intrinsic::riscv_cv_alu_subuRN;
     break;
 
+  // XAndesBFHCvt
+  case RISCV::BI__builtin_riscv_nds_fcvt_s_bf16:
+    return Builder.CreateFPExt(Ops[0], FloatTy);
+  case RISCV::BI__builtin_riscv_nds_fcvt_bf16_s:
+    return Builder.CreateFPTrunc(Ops[0], BFloatTy);
+
     // Vector builtins are handled from here.
 #include "clang/Basic/riscv_vector_builtin_cg.inc"
 

clang/lib/Headers/CMakeLists.txt

@@ -127,6 +127,7 @@ set(riscv_files
   riscv_bitmanip.h
   riscv_corev_alu.h
   riscv_crypto.h
+  riscv_nds.h
   riscv_ntlh.h
   sifive_vector.h
   andes_vector.h

clang/lib/Headers/riscv_nds.h

@@ -0,0 +1,35 @@
+/*===---- riscv_nds.h - Andes intrinsics -----------------------------------===
+ *
+ * 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
+ *
+ *===-----------------------------------------------------------------------===
+ */
+
+#ifndef __RISCV_NDS_H
+#define __RISCV_NDS_H
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+#if defined(__riscv_xandesbfhcvt)
+
+#define __DEFAULT_FN_ATTRS __attribute__((__always_inline__, __nodebug__))
+
+static __inline__ float __DEFAULT_FN_ATTRS __riscv_nds_fcvt_s_bf16(__bf16 bf) {
+  return __builtin_riscv_nds_fcvt_s_bf16(bf);
+}
+
+static __inline__ __bf16 __DEFAULT_FN_ATTRS __riscv_nds_fcvt_bf16_s(float sf) {
+  return __builtin_riscv_nds_fcvt_bf16_s(sf);
+}
+
+#endif // defined(__riscv_xandesbfhcvt)
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif // define __RISCV_NDS_H

clang/test/CodeGen/RISCV/riscv-xandesbfhcvt-c-api.c

@@ -0,0 +1,25 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -triple riscv32 -target-feature +xandesbfhcvt -emit-llvm %s -o - \
+// RUN:   -disable-O0-optnone | opt -S -passes=mem2reg | FileCheck %s
+// RUN: %clang_cc1 -triple riscv64 -target-feature +xandesbfhcvt -emit-llvm %s -o - \
+// RUN:   -disable-O0-optnone | opt -S -passes=mem2reg | FileCheck %s
+
+#include <riscv_nds.h>
+
+// CHECK-LABEL: @test_fcvt_s_bf16(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = fpext bfloat [[BF:%.*]] to float
+// CHECK-NEXT:    ret float [[TMP0]]
+//
+float test_fcvt_s_bf16(__bf16 bf) {
+  return __riscv_nds_fcvt_s_bf16(bf);
+}
+
+// CHECK-LABEL: @test_fcvt_bf16_s(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = fptrunc float [[SF:%.*]] to bfloat
+// CHECK-NEXT:    ret bfloat [[TMP0]]
+//
+__bf16 test_fcvt_bf16_s(float sf) {
+  return __riscv_nds_fcvt_bf16_s(sf);
+}

clang/test/CodeGen/RISCV/riscv-xandesbfhcvt.c

@@ -0,0 +1,23 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -triple riscv32 -target-feature +xandesbfhcvt -emit-llvm %s -o - \
+// RUN:   -disable-O0-optnone | opt -S -passes=mem2reg | FileCheck %s
+// RUN: %clang_cc1 -triple riscv64 -target-feature +xandesbfhcvt -emit-llvm %s -o - \
+// RUN:   -disable-O0-optnone | opt -S -passes=mem2reg | FileCheck %s
+
+// CHECK-LABEL: @test_fcvt_s_bf16(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = fpext bfloat [[BF:%.*]] to float
+// CHECK-NEXT:    ret float [[TMP0]]
+//
+float test_fcvt_s_bf16(__bf16 bf) {
+  return __builtin_riscv_nds_fcvt_s_bf16(bf);
+}
+
+// CHECK-LABEL: @test_fcvt_bf16_s(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[TMP0:%.*]] = fptrunc float [[SF:%.*]] to bfloat
+// CHECK-NEXT:    ret bfloat [[TMP0]]
+//
+__bf16 test_fcvt_bf16_s(float sf) {
+  return __builtin_riscv_nds_fcvt_bf16_s(sf);
+}

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -128,7 +128,7 @@ RISCVTargetLowering::RISCVTargetLowering(const TargetMachine &TM,
 
   if (Subtarget.hasStdExtZfhmin())
     addRegisterClass(MVT::f16, &RISCV::FPR16RegClass);
-  if (Subtarget.hasStdExtZfbfmin())
+  if (Subtarget.hasStdExtZfbfmin() || Subtarget.hasVendorXAndesBFHCvt())
     addRegisterClass(MVT::bf16, &RISCV::FPR16RegClass);
   if (Subtarget.hasStdExtF())
     addRegisterClass(MVT::f32, &RISCV::FPR32RegClass);

llvm/lib/Target/RISCV/RISCVInstrInfoXAndes.td

@@ -767,6 +767,13 @@ def : Sh2AddPat<NDS_LEA_W_ZE>;
 def : Sh3AddPat<NDS_LEA_D_ZE>;
 } // Predicates = [HasVendorXAndesPerf, IsRV64]
 
+let Predicates = [HasVendorXAndesBFHCvt] in {
+def : Pat<(fpextend (bf16 FPR16:$rs)),
+          (NDS_FCVT_S_BF16 (bf16 FPR16:$rs))>;
+def : Pat<(bf16 (fpround FPR32:$rs)),
+          (NDS_FCVT_BF16_S FPR32:$rs)>;
+} // Predicates = [HasVendorXAndesBFHCvt]
+
 let Predicates = [HasVendorXAndesVBFHCvt] in {
 defm PseudoNDS_VFWCVT_S_BF16 : VPseudoVWCVT_S_BF16;
 defm PseudoNDS_VFNCVT_BF16_S : VPseudoVNCVT_BF16_S;

llvm/test/CodeGen/RISCV/xandesbfhcvt.ll

@@ -0,0 +1,27 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc -mtriple=riscv32 -mattr=+xandesbfhcvt -target-abi ilp32f \
+; RUN:   -verify-machineinstrs < %s | FileCheck %s
+; RUN: llc -mtriple=riscv64 -mattr=+xandesbfhcvt -target-abi lp64f \
+; RUN:   -verify-machineinstrs < %s | FileCheck %s
+
+declare bfloat @llvm.riscv.nds.fcvt.bf16.s(float)
+
+define float @fcvt_s_bf16(bfloat %a) nounwind {
+; CHECK-LABEL: fcvt_s_bf16:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    nds.fcvt.s.bf16 fa0, fa0
+; CHECK-NEXT:    ret
+  %1 = fpext bfloat %a to float
+  ret float %1
+}
+
+declare float @llvm.riscv.nds.fcvt.s.bf16(bfloat)
+
+define bfloat @fcvt_bf16_s(float %a) nounwind {
+; CHECK-LABEL: fcvt_bf16_s:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    nds.fcvt.bf16.s fa0, fa0
+; CHECK-NEXT:    ret
+  %1 = fptrunc float %a to bfloat
+  ret bfloat %1
+}