https://github.com/E00N777 created 
https://github.com/llvm/llvm-project/pull/185852

Part of #185382.

Lower `__builtin_neon_vduph_lane_bf16` and
`__builtin_neon_vduph_laneq_bf16` in ClangIR to `cir.vec.extract`,
and add dedicated AArch64 Neon BF16 tests.

This is my first LLVM PR, so I'd really appreciate any suggestions on
the implementation, test structure, or general LLVM contribution style.


>From a992a797b28ca8b5445252955fc1584ac003f0f2 Mon Sep 17 00:00:00 2001
From: E0N777 <[email protected]>
Date: Wed, 11 Mar 2026 18:20:45 +0800
Subject: [PATCH] [CIR][AArch64] Lower BF16 vduph lane builtins

---
 .../lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp  | 12 ++++++--
 clang/test/CodeGen/AArch64/neon/bf16-vduph.c  | 30 +++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 clang/test/CodeGen/AArch64/neon/bf16-vduph.c

diff --git a/clang/lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp 
b/clang/lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp
index 5534e69b5f8bc..564d3e47a8c24 100644
--- a/clang/lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp
+++ b/clang/lib/CIR/CodeGen/CIRGenBuiltinAArch64.cpp
@@ -2802,10 +2802,8 @@ CIRGenFunction::emitAArch64BuiltinExpr(unsigned 
builtinID, const CallExpr *expr,
   case NEON::BI__builtin_neon_vqdmlsls_lane_s32:
   case NEON::BI__builtin_neon_vqdmlsls_laneq_s32:
   case NEON::BI__builtin_neon_vget_lane_bf16:
-  case NEON::BI__builtin_neon_vduph_lane_bf16:
   case NEON::BI__builtin_neon_vduph_lane_f16:
   case NEON::BI__builtin_neon_vgetq_lane_bf16:
-  case NEON::BI__builtin_neon_vduph_laneq_bf16:
   case NEON::BI__builtin_neon_vduph_laneq_f16:
   case NEON::BI__builtin_neon_vcvt_bf16_f32:
   case NEON::BI__builtin_neon_vcvtq_low_bf16_f32:
@@ -2824,6 +2822,16 @@ CIRGenFunction::emitAArch64BuiltinExpr(unsigned 
builtinID, const CallExpr *expr,
     return mlir::Value{};
   }
 
+  switch (builtinID) {
+  default:
+    break;
+  case NEON::BI__builtin_neon_vduph_lane_bf16:
+  case NEON::BI__builtin_neon_vduph_laneq_bf16: {
+    uint64_t index = getZExtIntValueFromConstOp(ops[1]);
+    return builder.createExtractElement(loc, ops[0], index);
+  }
+  }
+
   cir::VectorType ty = getNeonType(this, type, loc);
   if (!ty)
     return nullptr;
diff --git a/clang/test/CodeGen/AArch64/neon/bf16-vduph.c 
b/clang/test/CodeGen/AArch64/neon/bf16-vduph.c
new file mode 100644
index 0000000000000..e38383f567d98
--- /dev/null
+++ b/clang/test/CodeGen/AArch64/neon/bf16-vduph.c
@@ -0,0 +1,30 @@
+// REQUIRES: aarch64-registered-target || arm-registered-target
+
+// RUN:                   %clang_cc1 -triple arm64-none-linux-gnu 
-target-feature +neon -target-feature +bf16 -disable-O0-optnone 
-flax-vector-conversions=none           -emit-llvm -o - %s | opt -S 
-passes=mem2reg,sroa | FileCheck %s --check-prefixes=LLVM
+// RUN: %if cir-enabled %{%clang_cc1 -triple arm64-none-linux-gnu 
-target-feature +neon -target-feature +bf16 -disable-O0-optnone 
-flax-vector-conversions=none -fclangir -emit-llvm -o - %s | opt -S 
-passes=mem2reg,sroa | FileCheck %s --check-prefixes=LLVM %}
+// RUN: %if cir-enabled %{%clang_cc1 -triple arm64-none-linux-gnu 
-target-feature +neon -target-feature +bf16 -disable-O0-optnone 
-flax-vector-conversions=none -fclangir -emit-cir  -o - %s |                    
           FileCheck %s --check-prefixes=CIR %}
+
+typedef __bf16 bfloat16_t;
+typedef __attribute__((neon_vector_type(4))) bfloat16_t bfloat16x4_t;
+typedef __attribute__((neon_vector_type(8))) bfloat16_t bfloat16x8_t;
+
+// LLVM-LABEL: @test_vduph_lane_bf16(
+// LLVM-SAME: <4 x bfloat> {{.*}} [[V:%.*]])
+// LLVM:      [[VGET_LANE:%.*]] = extractelement <4 x bfloat> [[V]], 
i{{32|64}} 1
+// LLVM:      ret bfloat [[VGET_LANE]]
+// CIR-LABEL: @test_vduph_lane_bf16(
+// CIR:       cir.vec.extract %{{.*}}[%{{.*}} : !u64i] : !cir.vector<4 x 
!cir.bf16>
+bfloat16_t test_vduph_lane_bf16(bfloat16x4_t v) {
+  return __builtin_bit_cast(bfloat16_t, __builtin_neon_vduph_lane_bf16(v, 1));
+}
+
+// LLVM-LABEL: @test_vduph_laneq_bf16(
+// LLVM-SAME: <8 x bfloat> {{.*}} [[V:%.*]])
+// LLVM:      [[VGETQ_LANE:%.*]] = extractelement <8 x bfloat> [[V]], 
i{{32|64}} 7
+// LLVM:      ret bfloat [[VGETQ_LANE]]
+// CIR-LABEL: @test_vduph_laneq_bf16(
+// CIR:       cir.vec.extract %{{.*}}[%{{.*}} : !u64i] : !cir.vector<8 x 
!cir.bf16>
+bfloat16_t test_vduph_laneq_bf16(bfloat16x8_t v) {
+  return __builtin_bit_cast(bfloat16_t,
+                            __builtin_neon_vduph_laneq_bf16(v, 7));
+}

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