[llvm] [X86][BF16] Add subvec_zero_lowering patterns (PR #76507)

[Phoebe Wang via llvm-commits]

https://github.com/phoebewang updated https://github.com/llvm/llvm-project/pull/76507

>From b2b15670886c4e1771e6294343992ca766780999 Mon Sep 17 00:00:00 2001
From: Phoebe Wang <phoebe.wang at intel.com>
Date: Thu, 28 Dec 2023 22:16:09 +0800
Subject: [PATCH 1/2] [X86][BF16] Add subvec_zero_lowering patterns

---
 llvm/lib/Target/X86/X86ISelLowering.cpp    |  2 +-
 llvm/lib/Target/X86/X86InstrVecCompiler.td |  9 +++++++++
 llvm/test/CodeGen/X86/bfloat.ll            | 14 ++++++++++++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 35e54ebd5129f7..57ada84bbeffad 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3743,7 +3743,7 @@ static SDValue getZeroVector(MVT VT, const X86Subtarget &Subtarget,
   SDValue Vec;
   if (!Subtarget.hasSSE2() && VT.is128BitVector()) {
     Vec = DAG.getConstantFP(+0.0, dl, MVT::v4f32);
-  } else if (VT.isFloatingPoint()) {
+  } else if (VT.isFloatingPoint() && VT.getVectorElementType() != MVT::bf16) {
     Vec = DAG.getConstantFP(+0.0, dl, VT);
   } else if (VT.getVectorElementType() == MVT::i1) {
     assert((Subtarget.hasBWI() || VT.getVectorNumElements() <= 16) &&
diff --git a/llvm/lib/Target/X86/X86InstrVecCompiler.td b/llvm/lib/Target/X86/X86InstrVecCompiler.td
index 70bd77bba03ab3..bbd19cf8d5b25e 100644
--- a/llvm/lib/Target/X86/X86InstrVecCompiler.td
+++ b/llvm/lib/Target/X86/X86InstrVecCompiler.td
@@ -130,6 +130,9 @@ let Predicates = [HasAVX, NoVLX] in {
   defm : subvec_zero_lowering<"DQA", VR128, v32i8, v16i8, sub_xmm>;
 }
 
+let Predicates = [HasAVXNECONVERT, NoVLX] in
+  defm : subvec_zero_lowering<"DQA", VR128, v16bf16, v8bf16, sub_xmm>;
+
 let Predicates = [HasVLX] in {
   defm : subvec_zero_lowering<"APDZ128", VR128X, v4f64, v2f64, sub_xmm>;
   defm : subvec_zero_lowering<"APSZ128", VR128X, v8f32, v4f32, sub_xmm>;
@@ -175,6 +178,12 @@ let Predicates = [HasFP16, HasVLX] in {
   defm : subvec_zero_lowering<"APSZ256", VR256X, v32f16, v16f16, sub_ymm>;
 }
 
+let Predicates = [HasBF16, HasVLX] in {
+  defm : subvec_zero_lowering<"APSZ128", VR128X, v16bf16, v8bf16, sub_xmm>;
+  defm : subvec_zero_lowering<"APSZ128", VR128X, v32bf16, v8bf16, sub_xmm>;
+  defm : subvec_zero_lowering<"APSZ256", VR256X, v32bf16, v16bf16, sub_ymm>;
+}
+
 class maskzeroupper<ValueType vt, RegisterClass RC> :
   PatLeaf<(vt RC:$src), [{
     return isMaskZeroExtended(N);
diff --git a/llvm/test/CodeGen/X86/bfloat.ll b/llvm/test/CodeGen/X86/bfloat.ll
index 674a0eacb0ca98..9c65310f79d7ec 100644
--- a/llvm/test/CodeGen/X86/bfloat.ll
+++ b/llvm/test/CodeGen/X86/bfloat.ll
@@ -2529,3 +2529,17 @@ define <8 x bfloat> @extract_v32bf16_v8bf16(<32 x bfloat> %x) {
   %a = shufflevector <32 x bfloat> %x, <32 x bfloat> undef, <8 x i32> <i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
   ret <8 x bfloat> %a
 }
+
+define <16 x bfloat> @concat_zero_v8bf16(<8 x bfloat> %x, <8 x bfloat> %y) {
+; SSE2-LABEL: concat_zero_v8bf16:
+; SSE2:       # %bb.0:
+; SSE2-NEXT:    xorps %xmm1, %xmm1
+; SSE2-NEXT:    retq
+;
+; AVX-LABEL: concat_zero_v8bf16:
+; AVX:       # %bb.0:
+; AVX-NEXT:    vmovaps %xmm0, %xmm0
+; AVX-NEXT:    retq
+  %a = shufflevector <8 x bfloat> %x, <8 x bfloat> zeroinitializer, <16 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 7, i32 8, i32 9, i32 10, i32 11, i32 12, i32 13, i32 14, i32 15>
+  ret <16 x bfloat> %a
+}

>From 6319b7a092aa594fadb8d4f9f4a0cdd2f38cb791 Mon Sep 17 00:00:00 2001
From: Phoebe Wang <phoebe.wang at intel.com>
Date: Sun, 31 Dec 2023 11:08:19 +0800
Subject: [PATCH 2/2] Use isTypeLegal

---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 57ada84bbeffad..a90ddf132c3897 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3741,9 +3741,11 @@ static SDValue getZeroVector(MVT VT, const X86Subtarget &Subtarget,
   // type. This ensures they get CSE'd. But if the integer type is not
   // available, use a floating-point +0.0 instead.
   SDValue Vec;
+  const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   if (!Subtarget.hasSSE2() && VT.is128BitVector()) {
     Vec = DAG.getConstantFP(+0.0, dl, MVT::v4f32);
-  } else if (VT.isFloatingPoint() && VT.getVectorElementType() != MVT::bf16) {
+  } else if (VT.isFloatingPoint() &&
+             TLI.isTypeLegal(VT.getVectorElementType())) {
     Vec = DAG.getConstantFP(+0.0, dl, VT);
   } else if (VT.getVectorElementType() == MVT::i1) {
     assert((Subtarget.hasBWI() || VT.getVectorNumElements() <= 16) &&