[llvm] [AArch64] Lower extending sitofp using tbl (PR #92528)

Momchil Velikov via llvm-commits llvm-commits at lists.llvm.org
Tue May 28 06:48:41 PDT 2024


https://github.com/momchil-velikov updated https://github.com/llvm/llvm-project/pull/92528

>From edc49a58a4984c3a97f12de659edf72b3621d593 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Tue, 21 May 2024 15:07:17 +0100
Subject: [PATCH 1/5] [AArch64] Add patterns for conversions using fixed-point
 scvtf

Change-Id: If19131b160484aba942dbbef042fb67f0b98561d
---
 .../Target/AArch64/AArch64ISelLowering.cpp    |   2 +-
 llvm/lib/Target/AArch64/AArch64InstrInfo.td   |  25 +++++
 .../AArch64/fixed-point-conv-vec-pat.ll       | 103 ++++++++++++++++++
 3 files changed, 129 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 25ba8d8500306..4dd44d9972092 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -14337,7 +14337,7 @@ SDValue AArch64TargetLowering::LowerVectorSRA_SRL_SHL(SDValue Op,
       unsigned Opc =
           (Op.getOpcode() == ISD::SRA) ? AArch64ISD::VASHR : AArch64ISD::VLSHR;
       return DAG.getNode(Opc, DL, VT, Op.getOperand(0),
-                         DAG.getConstant(Cnt, DL, MVT::i32));
+                         DAG.getConstant(Cnt, DL, MVT::i32), Op->getFlags());
     }
 
     // Right shift register.  Note, there is not a shift right register
diff --git a/llvm/lib/Target/AArch64/AArch64InstrInfo.td b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
index 4830033b23527..dd54520c8ddad 100644
--- a/llvm/lib/Target/AArch64/AArch64InstrInfo.td
+++ b/llvm/lib/Target/AArch64/AArch64InstrInfo.td
@@ -733,6 +733,12 @@ def AArch64rev64 : SDNode<"AArch64ISD::REV64", SDT_AArch64UnaryVec>;
 def AArch64ext : SDNode<"AArch64ISD::EXT", SDT_AArch64ExtVec>;
 
 def AArch64vashr : SDNode<"AArch64ISD::VASHR", SDT_AArch64vshift>;
+
+def AArch64vashr_exact : PatFrag<(ops          node:$lhs, node:$rhs),
+                                 (AArch64vashr node:$lhs, node:$rhs), [{
+  return N->getFlags().hasExact();
+}]>;
+
 def AArch64vlshr : SDNode<"AArch64ISD::VLSHR", SDT_AArch64vshift>;
 def AArch64vshl : SDNode<"AArch64ISD::VSHL", SDT_AArch64vshift>;
 def AArch64sqshli : SDNode<"AArch64ISD::SQSHL_I", SDT_AArch64vshift>;
@@ -7710,6 +7716,25 @@ defm SCVTF: SIMDVectorRShiftToFP<0, 0b11100, "scvtf",
 defm RSHRN   : SIMDVectorRShiftNarrowBHS<0, 0b10001, "rshrn", AArch64rshrn>;
 defm SHL     : SIMDVectorLShiftBHSD<0, 0b01010, "shl", AArch64vshl>;
 
+let Predicates = [HasNEON] in {
+def : Pat<(v2f32 (sint_to_fp (v2i32 (AArch64vashr_exact v2i32:$Vn, i32:$shift)))),
+          (SCVTFv2i32_shift $Vn, vecshiftR32:$shift)>;
+
+def : Pat<(v4f32 (sint_to_fp (v4i32 (AArch64vashr_exact v4i32:$Vn, i32:$shift)))),
+          (SCVTFv4i32_shift $Vn, vecshiftR32:$shift)>;
+
+def : Pat<(v2f64 (sint_to_fp (v2i64 (AArch64vashr_exact v2i64:$Vn, i32:$shift)))),
+          (SCVTFv2i64_shift $Vn, vecshiftR64:$shift)>;
+}
+
+let Predicates = [HasNEON, HasFullFP16] in {
+def : Pat<(v4f16 (sint_to_fp (v4i16 (AArch64vashr_exact v4i16:$Vn, i32:$shift)))),
+          (SCVTFv4i16_shift $Vn, vecshiftR16:$shift)>;
+
+def : Pat<(v8f16 (sint_to_fp (v8i16 (AArch64vashr_exact v8i16:$Vn, i32:$shift)))),
+          (SCVTFv8i16_shift $Vn, vecshiftR16:$shift)>;
+}
+
 // X << 1 ==> X + X
 class SHLToADDPat<ValueType ty, RegisterClass regtype>
   : Pat<(ty (AArch64vshl (ty regtype:$Rn), (i32 1))),
diff --git a/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll b/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll
new file mode 100644
index 0000000000000..7141b5b03a1ac
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll
@@ -0,0 +1,103 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 5
+; RUN: llc < %s | FileCheck %s
+
+target triple = "aarch64"
+
+; First some corner cases
+define <4 x float> @f_v4_s0(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s0:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.4s, v0.4s
+; CHECK-NEXT:    ret
+  %s = ashr exact <4 x i32> %u, <i32 0, i32 0, i32 0, i32 0>
+  %v = sitofp <4 x i32> %s to <4 x float>
+  ret <4 x float> %v
+}
+
+define <4 x float> @f_v4_s1(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s1:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.4s, v0.4s, #1
+; CHECK-NEXT:    ret
+  %s = ashr exact <4 x i32> %u, <i32 1, i32 1, i32 1, i32 1>
+  %v = sitofp <4 x i32> %s to <4 x float>
+  ret <4 x float> %v
+}
+
+define <4 x float> @f_v4_s24_inexact(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s24_inexact:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    sshr v0.4s, v0.4s, #24
+; CHECK-NEXT:    scvtf v0.4s, v0.4s
+; CHECK-NEXT:    ret
+  %s = ashr <4 x i32> %u, <i32 24, i32 24, i32 24, i32 24>
+  %v = sitofp <4 x i32> %s to <4 x float>
+  ret <4 x float> %v
+}
+
+define <4 x float> @f_v4_s32(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s32:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    movi v0.2d, #0000000000000000
+; CHECK-NEXT:    ret
+  %s = ashr <4 x i32> %u, <i32 32, i32 32, i32 32, i32 32>
+  %v = sitofp <4 x i32> %s to <4 x float>
+  ret <4 x float> %v
+}
+
+; Common cases for conversion from signed integer to floating point types
+define <2 x float> @f_v2_s24(<2 x i32> %u) {
+; CHECK-LABEL: f_v2_s24:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.2s, v0.2s, #24
+; CHECK-NEXT:    ret
+  %s = ashr exact <2 x i32> %u, <i32 24, i32 24>
+  %v = sitofp <2 x i32> %s to <2 x float>
+  ret <2 x float> %v
+}
+
+define <4 x float> @f_v4_s24(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s24:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.4s, v0.4s, #24
+; CHECK-NEXT:    ret
+  %s = ashr exact <4 x i32> %u, <i32 24, i32 24, i32 24, i32 24>
+  %v = sitofp <4 x i32> %s to <4 x float>
+  ret <4 x float> %v
+}
+
+; Check legalisation to <2 x f64> does not get in the way
+define <8 x double> @d_v8_s64(<8 x i64> %u) {
+; CHECK-LABEL: d_v8_s64:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.2d, v0.2d, #56
+; CHECK-NEXT:    scvtf v1.2d, v1.2d, #56
+; CHECK-NEXT:    scvtf v2.2d, v2.2d, #56
+; CHECK-NEXT:    scvtf v3.2d, v3.2d, #56
+; CHECK-NEXT:    ret
+  %s = ashr exact <8 x i64> %u, <i64 56, i64 56, i64 56, i64 56, i64 56, i64 56, i64 56, i64 56>
+  %v = sitofp <8 x i64> %s to <8 x double>
+  ret <8 x double> %v
+}
+
+define <4 x half> @h_v4_s8(<4 x i16> %u) #0 {
+; CHECK-LABEL: h_v4_s8:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.4h, v0.4h, #8
+; CHECK-NEXT:    ret
+  %s = ashr exact <4 x i16> %u, <i16 8, i16 8, i16 8, i16 8>
+  %v = sitofp <4 x i16> %s to <4 x half>
+  ret <4 x half> %v
+}
+
+define <8 x half> @h_v8_s8(<8 x i16> %u) #0 {
+; CHECK-LABEL: h_v8_s8:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    scvtf v0.8h, v0.8h, #8
+; CHECK-NEXT:    ret
+  %s = ashr exact <8 x i16> %u, <i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8, i16 8>
+  %v = sitofp <8 x i16> %s to <8 x half>
+  ret <8 x half> %v
+}
+
+attributes #0 = { "target-features"="+fullfp16"}

>From a28dc1b78cdeda13d1c1640065a7ee3a41cc636d Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Tue, 28 May 2024 11:02:05 +0100
Subject: [PATCH 2/5] [fixup] Remove UB from a test (shift right by 32)

Change-Id: Ie80a97a0124b057394ba2b8a2f1158591af1af5a
---
 llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll b/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll
index 7141b5b03a1ac..dff216192a6c3 100644
--- a/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll
+++ b/llvm/test/CodeGen/AArch64/fixed-point-conv-vec-pat.ll
@@ -35,12 +35,13 @@ define <4 x float> @f_v4_s24_inexact(<4 x i32> %u) {
   ret <4 x float> %v
 }
 
-define <4 x float> @f_v4_s32(<4 x i32> %u) {
-; CHECK-LABEL: f_v4_s32:
+define <4 x float> @f_v4_s31(<4 x i32> %u) {
+; CHECK-LABEL: f_v4_s31:
 ; CHECK:       // %bb.0:
-; CHECK-NEXT:    movi v0.2d, #0000000000000000
+; CHECK-NEXT:    cmlt v0.4s, v0.4s, #0
+; CHECK-NEXT:    scvtf v0.4s, v0.4s
 ; CHECK-NEXT:    ret
-  %s = ashr <4 x i32> %u, <i32 32, i32 32, i32 32, i32 32>
+  %s = ashr <4 x i32> %u, <i32 31, i32 31, i32 31, i32 31>
   %v = sitofp <4 x i32> %s to <4 x float>
   ret <4 x float> %v
 }

>From fae9ee5f8f1704aaa7dcfd284c5c182757664973 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Fri, 17 May 2024 11:50:31 +0100
Subject: [PATCH 3/5] [AArch64] Refactor creation of a shuffle mask for TBL
 (NFC)

---
 .../Target/AArch64/AArch64ISelLowering.cpp    | 88 +++++++++++--------
 1 file changed, 50 insertions(+), 38 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 4dd44d9972092..ec16bc1932721 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -15719,48 +15719,51 @@ bool AArch64TargetLowering::shouldSinkOperands(
   return false;
 }
 
-static bool createTblShuffleForZExt(ZExtInst *ZExt, FixedVectorType *DstTy,
-                                    bool IsLittleEndian) {
-  Value *Op = ZExt->getOperand(0);
-  auto *SrcTy = cast<FixedVectorType>(Op->getType());
-  auto SrcWidth = cast<IntegerType>(SrcTy->getElementType())->getBitWidth();
-  auto DstWidth = cast<IntegerType>(DstTy->getElementType())->getBitWidth();
+static bool createTblShuffleMask(unsigned SrcWidth, unsigned DstWidth,
+                                 unsigned NumElts, bool IsLittleEndian,
+                                 SmallVectorImpl<int> &Mask) {
   if (DstWidth % 8 != 0 || DstWidth <= 16 || DstWidth >= 64)
     return false;
 
-  assert(DstWidth % SrcWidth == 0 &&
-         "TBL lowering is not supported for a ZExt instruction with this "
-         "source & destination element type.");
-  unsigned ZExtFactor = DstWidth / SrcWidth;
+  if (DstWidth % SrcWidth != 0)
+    return false;
+
+  unsigned Factor = DstWidth / SrcWidth;
+  unsigned MaskLen = NumElts * Factor;
+
+  Mask.clear();
+  Mask.resize(MaskLen, NumElts);
+
+  unsigned SrcIndex = 0;
+  for (unsigned I = 0; I < MaskLen; I += Factor)
+    Mask[I] = SrcIndex++;
+
+  if (!IsLittleEndian)
+    std::rotate(Mask.rbegin(), Mask.rbegin() + Factor - 1, Mask.rend());
+
+  return true;
+}
+
+static Value *createTblShuffleForZExt(IRBuilderBase &Builder, Value *Op,
+                                      FixedVectorType *ZExtTy,
+                                      FixedVectorType *DstTy,
+                                      bool IsLittleEndian) {
+  auto *SrcTy = cast<FixedVectorType>(Op->getType());
   unsigned NumElts = SrcTy->getNumElements();
-  IRBuilder<> Builder(ZExt);
+  auto SrcWidth = cast<IntegerType>(SrcTy->getElementType())->getBitWidth();
+  auto DstWidth = cast<IntegerType>(DstTy->getElementType())->getBitWidth();
+
   SmallVector<int> Mask;
-  // Create a mask that selects <0,...,Op[i]> for each lane of the destination
-  // vector to replace the original ZExt. This can later be lowered to a set of
-  // tbl instructions.
-  for (unsigned i = 0; i < NumElts * ZExtFactor; i++) {
-    if (IsLittleEndian) {
-      if (i % ZExtFactor == 0)
-        Mask.push_back(i / ZExtFactor);
-      else
-        Mask.push_back(NumElts);
-    } else {
-      if ((i + 1) % ZExtFactor == 0)
-        Mask.push_back((i - ZExtFactor + 1) / ZExtFactor);
-      else
-        Mask.push_back(NumElts);
-    }
-  }
+  if (!createTblShuffleMask(SrcWidth, DstWidth, NumElts, IsLittleEndian, Mask))
+    return nullptr;
 
   auto *FirstEltZero = Builder.CreateInsertElement(
       PoisonValue::get(SrcTy), Builder.getInt8(0), uint64_t(0));
   Value *Result = Builder.CreateShuffleVector(Op, FirstEltZero, Mask);
   Result = Builder.CreateBitCast(Result, DstTy);
-  if (DstTy != ZExt->getType())
-    Result = Builder.CreateZExt(Result, ZExt->getType());
-  ZExt->replaceAllUsesWith(Result);
-  ZExt->eraseFromParent();
-  return true;
+  if (DstTy != ZExtTy)
+    Result = Builder.CreateZExt(Result, ZExtTy);
+  return Result;
 }
 
 static void createTblForTrunc(TruncInst *TI, bool IsLittleEndian) {
@@ -15925,21 +15928,30 @@ bool AArch64TargetLowering::optimizeExtendOrTruncateConversion(
 
       DstTy = TruncDstType;
     }
-
-    return createTblShuffleForZExt(ZExt, DstTy, Subtarget->isLittleEndian());
+    IRBuilder<> Builder(ZExt);
+    Value *Result = createTblShuffleForZExt(
+        Builder, ZExt->getOperand(0), cast<FixedVectorType>(ZExt->getType()),
+        DstTy, Subtarget->isLittleEndian());
+    if (!Result)
+      return false;
+    ZExt->replaceAllUsesWith(Result);
+    ZExt->eraseFromParent();
+    return true;
   }
 
   auto *UIToFP = dyn_cast<UIToFPInst>(I);
   if (UIToFP && SrcTy->getElementType()->isIntegerTy(8) &&
       DstTy->getElementType()->isFloatTy()) {
     IRBuilder<> Builder(I);
-    auto *ZExt = cast<ZExtInst>(
-        Builder.CreateZExt(I->getOperand(0), VectorType::getInteger(DstTy)));
+    Value *ZExt = createTblShuffleForZExt(
+        Builder, I->getOperand(0), FixedVectorType::getInteger(DstTy),
+        FixedVectorType::getInteger(DstTy), Subtarget->isLittleEndian());
+    if (!ZExt)
+      return false;
     auto *UI = Builder.CreateUIToFP(ZExt, DstTy);
     I->replaceAllUsesWith(UI);
     I->eraseFromParent();
-    return createTblShuffleForZExt(ZExt, cast<FixedVectorType>(ZExt->getType()),
-                                   Subtarget->isLittleEndian());
+    return true;
   }
 
   // Convert 'fptoui <(8|16) x float> to <(8|16) x i8>' to a wide fptoui

>From 17f7ab729c8f62c14d09e327a9429e5259a1004d Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Tue, 28 May 2024 14:35:33 +0100
Subject: [PATCH 4/5] [fixup] Simplify code

Change-Id: I0e51f00113d0692d5d3751c89eac8167511d1d9e
---
 llvm/lib/Target/AArch64/AArch64ISelLowering.cpp | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index ec16bc1932721..86cf8a387c247 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -15735,12 +15735,9 @@ static bool createTblShuffleMask(unsigned SrcWidth, unsigned DstWidth,
   Mask.resize(MaskLen, NumElts);
 
   unsigned SrcIndex = 0;
-  for (unsigned I = 0; I < MaskLen; I += Factor)
+  for (unsigned I = IsLittleEndian ? 0 : Factor - 1; I < MaskLen; I += Factor)
     Mask[I] = SrcIndex++;
 
-  if (!IsLittleEndian)
-    std::rotate(Mask.rbegin(), Mask.rbegin() + Factor - 1, Mask.rend());
-
   return true;
 }
 

>From 550b8382bc43cc2bc6c145a34da529a3314b224d Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Tue, 21 May 2024 15:57:16 +0100
Subject: [PATCH 5/5] [AArch64] Lower extending sitofp using tbl

In a similar manner as in https://reviews.llvm.org/D133494
use `TBL` to place bytes in the *upper* part of `i32` elements
and then convert to float using fixed-point `scvtf`, i.e.

    scvtf Vd.4s, Vn.4s, #24

Change-Id: Ib9df3e4243612cbee8560907b24b14e76b61f265
---
 llvm/lib/CodeGen/CodeGenPrepare.cpp           |   3 +-
 .../Target/AArch64/AArch64ISelLowering.cpp    |  35 ++++
 llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll    | 196 ++++++++++++++++++
 3 files changed, 233 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll

diff --git a/llvm/lib/CodeGen/CodeGenPrepare.cpp b/llvm/lib/CodeGen/CodeGenPrepare.cpp
index 339a1f1f2f002..4c52dbfa23903 100644
--- a/llvm/lib/CodeGen/CodeGenPrepare.cpp
+++ b/llvm/lib/CodeGen/CodeGenPrepare.cpp
@@ -8333,7 +8333,8 @@ bool CodeGenPrepare::optimizeInst(Instruction *I, ModifyDT &ModifiedDT) {
     if (OptimizeNoopCopyExpression(CI, *TLI, *DL))
       return true;
 
-    if ((isa<UIToFPInst>(I) || isa<FPToUIInst>(I) || isa<TruncInst>(I)) &&
+    if ((isa<UIToFPInst>(I) || isa<SIToFPInst>(I) || isa<FPToUIInst>(I) ||
+         isa<TruncInst>(I)) &&
         TLI->optimizeExtendOrTruncateConversion(
             I, LI->getLoopFor(I->getParent()), *TTI))
       return true;
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index 86cf8a387c247..1da63ce0767d3 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -15763,6 +15763,24 @@ static Value *createTblShuffleForZExt(IRBuilderBase &Builder, Value *Op,
   return Result;
 }
 
+static Value *createTblShuffleForSExt(IRBuilderBase &Builder, Value *Op,
+                                      FixedVectorType *DstTy,
+                                      bool IsLittleEndian) {
+  auto *SrcTy = cast<FixedVectorType>(Op->getType());
+  auto SrcWidth = cast<IntegerType>(SrcTy->getElementType())->getBitWidth();
+  auto DstWidth = cast<IntegerType>(DstTy->getElementType())->getBitWidth();
+
+  SmallVector<int> Mask;
+  if (!createTblShuffleMask(SrcWidth, DstWidth, SrcTy->getNumElements(),
+                            !IsLittleEndian, Mask))
+    return nullptr;
+
+  auto *FirstEltZero = Builder.CreateInsertElement(
+      PoisonValue::get(SrcTy), Builder.getInt8(0), uint64_t(0));
+
+  return Builder.CreateShuffleVector(Op, FirstEltZero, Mask);
+}
+
 static void createTblForTrunc(TruncInst *TI, bool IsLittleEndian) {
   IRBuilder<> Builder(TI);
   SmallVector<Value *> Parts;
@@ -15951,6 +15969,23 @@ bool AArch64TargetLowering::optimizeExtendOrTruncateConversion(
     return true;
   }
 
+  auto *SIToFP = dyn_cast<SIToFPInst>(I);
+  if (SIToFP && SrcTy->getElementType()->isIntegerTy(8) &&
+      DstTy->getElementType()->isFloatTy()) {
+    IRBuilder<> Builder(I);
+    auto *Shuffle = createTblShuffleForSExt(Builder, I->getOperand(0),
+                                            FixedVectorType::getInteger(DstTy),
+                                            Subtarget->isLittleEndian());
+    if (!Shuffle)
+      return false;
+    auto *Cast = Builder.CreateBitCast(Shuffle, VectorType::getInteger(DstTy));
+    auto *AShr = Builder.CreateAShr(Cast, 24, "", true);
+    auto *SI = Builder.CreateSIToFP(AShr, DstTy);
+    I->replaceAllUsesWith(SI);
+    I->eraseFromParent();
+    return true;
+  }
+
   // Convert 'fptoui <(8|16) x float> to <(8|16) x i8>' to a wide fptoui
   // followed by a truncate lowered to using tbl.4.
   auto *FPToUI = dyn_cast<FPToUIInst>(I);
diff --git a/llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll b/llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll
new file mode 100644
index 0000000000000..b7e8a3a3defe4
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/sitofp-to-tbl.ll
@@ -0,0 +1,196 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
+; RUN: llc -verify-machineinstrs < %s | FileCheck %s
+
+target triple = "aarch64-linux"
+
+; CHECK-LABEL: .LCPI0_0:
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    4
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    5
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    6
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    7
+; CHECK-NEXT:  .LCPI0_1:
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    0
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    1
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    2
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+; CHECK-NEXT:  .byte    255
+
+define void @sitofp_v8i8_to_v8f32(ptr %src, ptr %dst) {
+; CHECK-LABEL: sitofp_v8i8_to_v8f32:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    adrp x8, .LCPI0_0
+; CHECK-NEXT:    adrp x9, .LCPI0_1
+; CHECK-NEXT:    ldr q0, [x8, :lo12:.LCPI0_0]
+; CHECK-NEXT:    ldr q1, [x9, :lo12:.LCPI0_1]
+; CHECK-NEXT:    mov x8, xzr
+; CHECK-NEXT:  .LBB0_1: // %loop
+; CHECK-NEXT:    // =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    ldr d2, [x0, x8, lsl #3]
+; CHECK-NEXT:    add x9, x1, x8, lsl #5
+; CHECK-NEXT:    add x8, x8, #1
+; CHECK-NEXT:    cmp x8, #1000
+; CHECK-NEXT:    tbl v3.16b, { v2.16b }, v0.16b
+; CHECK-NEXT:    tbl v2.16b, { v2.16b }, v1.16b
+; CHECK-NEXT:    scvtf v3.4s, v3.4s, #24
+; CHECK-NEXT:    scvtf v2.4s, v2.4s, #24
+; CHECK-NEXT:    stp q2, q3, [x9]
+; CHECK-NEXT:    b.eq .LBB0_1
+; CHECK-NEXT:  // %bb.2: // %exit
+; CHECK-NEXT:    ret
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %gep.src = getelementptr inbounds <8 x i8>, ptr %src, i64 %iv
+  %l = load <8 x i8>, ptr %gep.src
+  %conv = sitofp <8 x i8> %l to <8 x float>
+  %gep.dst = getelementptr inbounds <8 x float>, ptr %dst, i64 %iv
+  store <8 x float> %conv, ptr %gep.dst
+  %iv.next = add i64 %iv, 1
+  %ec = icmp eq i64 %iv.next, 1000
+  br i1 %ec, label %loop, label %exit
+
+exit:
+  ret void
+}
+
+; CHECK-LABEL: .LCPI1_0:
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    12
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    13
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    14
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    15
+; CHECK-NEXT: .LCPI1_1:
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    8
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    9
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    10
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    11
+; CHECK-NEXT: .LCPI1_2:
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    4
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    5
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    6
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    7
+; CHECK-NEXT: .LCPI1_3:
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    0
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    1
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    2
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    255
+; CHECK-NEXT: .byte    3
+
+define void @sitofp_v16i8_to_v16f32(ptr %src, ptr %dst) {
+; CHECK-LABEL: sitofp_v16i8_to_v16f32:
+; CHECK:       // %bb.0: // %entry
+; CHECK-NEXT:    adrp x8, .LCPI1_0
+; CHECK-NEXT:    adrp x9, .LCPI1_1
+; CHECK-NEXT:    adrp x10, .LCPI1_2
+; CHECK-NEXT:    ldr q0, [x8, :lo12:.LCPI1_0]
+; CHECK-NEXT:    adrp x8, .LCPI1_3
+; CHECK-NEXT:    ldr q1, [x9, :lo12:.LCPI1_1]
+; CHECK-NEXT:    ldr q2, [x10, :lo12:.LCPI1_2]
+; CHECK-NEXT:    ldr q3, [x8, :lo12:.LCPI1_3]
+; CHECK-NEXT:    mov x8, xzr
+; CHECK-NEXT:  .LBB1_1: // %loop
+; CHECK-NEXT:    // =>This Inner Loop Header: Depth=1
+; CHECK-NEXT:    ldr q4, [x0, x8, lsl #4]
+; CHECK-NEXT:    add x9, x1, x8, lsl #6
+; CHECK-NEXT:    add x8, x8, #1
+; CHECK-NEXT:    cmp x8, #1000
+; CHECK-NEXT:    tbl v5.16b, { v4.16b }, v0.16b
+; CHECK-NEXT:    tbl v6.16b, { v4.16b }, v1.16b
+; CHECK-NEXT:    tbl v7.16b, { v4.16b }, v2.16b
+; CHECK-NEXT:    tbl v4.16b, { v4.16b }, v3.16b
+; CHECK-NEXT:    scvtf v5.4s, v5.4s, #24
+; CHECK-NEXT:    scvtf v6.4s, v6.4s, #24
+; CHECK-NEXT:    scvtf v7.4s, v7.4s, #24
+; CHECK-NEXT:    scvtf v4.4s, v4.4s, #24
+; CHECK-NEXT:    stp q6, q5, [x9, #32]
+; CHECK-NEXT:    stp q4, q7, [x9]
+; CHECK-NEXT:    b.eq .LBB1_1
+; CHECK-NEXT:  // %bb.2: // %exit
+; CHECK-NEXT:    ret
+entry:
+  br label %loop
+
+loop:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %loop ]
+  %gep.src = getelementptr inbounds <16 x i8>, ptr %src, i64 %iv
+  %l = load <16 x i8>, ptr %gep.src
+  %conv = sitofp <16 x i8> %l to <16 x float>
+  %gep.dst = getelementptr inbounds <16 x float>, ptr %dst, i64 %iv
+  store <16 x float> %conv, ptr %gep.dst
+  %iv.next = add i64 %iv, 1
+  %ec = icmp eq i64 %iv.next, 1000
+  br i1 %ec, label %loop, label %exit
+
+exit:
+  ret void
+}



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