[NVPTX] Implement computeKnownBitsForTargetNode for LoadV (llvm#154165)

kalxr · web-flow · commit 691ccf263aed · 2025-08-20T18:57:15.000Z
Remove AND combines as they are no longer needed after this.
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.cpp b/llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.cpp
@@ -1150,15 +1150,12 @@ bool NVPTXDAGToDAGISel::tryLoad(SDNode *N) {
   return true;
 }
 
-static unsigned getLoadStoreVectorNumElts(SDNode *N) {
+static unsigned getStoreVectorNumElts(SDNode *N) {
   switch (N->getOpcode()) {
-  case NVPTXISD::LoadV2:
   case NVPTXISD::StoreV2:
     return 2;
-  case NVPTXISD::LoadV4:
   case NVPTXISD::StoreV4:
     return 4;
-  case NVPTXISD::LoadV8:
   case NVPTXISD::StoreV8:
     return 8;
   default:
@@ -1171,7 +1168,6 @@ bool NVPTXDAGToDAGISel::tryLoadVector(SDNode *N) {
   const EVT MemEVT = LD->getMemoryVT();
   if (!MemEVT.isSimple())
     return false;
-  const MVT MemVT = MemEVT.getSimpleVT();
 
   // Address Space Setting
   const auto CodeAddrSpace = getAddrSpace(LD);
@@ -1191,18 +1187,15 @@ bool NVPTXDAGToDAGISel::tryLoadVector(SDNode *N) {
   // Float  : ISD::NON_EXTLOAD or ISD::EXTLOAD and the type is float
   // Read at least 8 bits (predicates are stored as 8-bit values)
   // The last operand holds the original LoadSDNode::getExtensionType() value
-  const unsigned TotalWidth = MemVT.getSizeInBits();
   const unsigned ExtensionType =
       N->getConstantOperandVal(N->getNumOperands() - 1);
   const unsigned FromType = (ExtensionType == ISD::SEXTLOAD)
                                 ? NVPTX::PTXLdStInstCode::Signed
                                 : NVPTX::PTXLdStInstCode::Untyped;
 
-  const unsigned FromTypeWidth = TotalWidth / getLoadStoreVectorNumElts(N);
+  const unsigned FromTypeWidth = getFromTypeWidthForLoad(LD);
 
   assert(!(EltVT.isVector() && ExtensionType != ISD::NON_EXTLOAD));
-  assert(isPowerOf2_32(FromTypeWidth) && FromTypeWidth >= 8 &&
-         FromTypeWidth <= 128 && TotalWidth <= 256 && "Invalid width for load");
 
   const auto [Base, Offset] = selectADDR(N->getOperand(1), CurDAG);
   SDValue Ops[] = {getI32Imm(Ordering, DL),
@@ -1247,30 +1240,23 @@ bool NVPTXDAGToDAGISel::tryLDG(MemSDNode *LD) {
   const EVT LoadedEVT = LD->getMemoryVT();
   if (!LoadedEVT.isSimple())
     return false;
-  const MVT LoadedVT = LoadedEVT.getSimpleVT();
 
   SDLoc DL(LD);
 
-  const unsigned TotalWidth = LoadedVT.getSizeInBits();
   unsigned ExtensionType;
-  unsigned NumElts;
   if (const auto *Load = dyn_cast<LoadSDNode>(LD)) {
     ExtensionType = Load->getExtensionType();
-    NumElts = 1;
   } else {
     ExtensionType = LD->getConstantOperandVal(LD->getNumOperands() - 1);
-    NumElts = getLoadStoreVectorNumElts(LD);
   }
   const unsigned FromType = (ExtensionType == ISD::SEXTLOAD)
                                 ? NVPTX::PTXLdStInstCode::Signed
                                 : NVPTX::PTXLdStInstCode::Untyped;
 
-  const unsigned FromTypeWidth = TotalWidth / NumElts;
+  const unsigned FromTypeWidth = getFromTypeWidthForLoad(LD);
 
   assert(!(LD->getSimpleValueType(0).isVector() &&
            ExtensionType != ISD::NON_EXTLOAD));
-  assert(isPowerOf2_32(FromTypeWidth) && FromTypeWidth >= 8 &&
-         FromTypeWidth <= 128 && TotalWidth <= 256 && "Invalid width for load");
 
   const auto [Base, Offset] = selectADDR(LD->getOperand(1), CurDAG);
   SDValue Ops[] = {getI32Imm(FromType, DL), getI32Imm(FromTypeWidth, DL), Base,
@@ -1309,26 +1295,21 @@ bool NVPTXDAGToDAGISel::tryLDG(MemSDNode *LD) {
   return true;
 }
 
+unsigned NVPTXDAGToDAGISel::getFromTypeWidthForLoad(const MemSDNode *Mem) {
+  auto TotalWidth = Mem->getMemoryVT().getSizeInBits();
+  auto NumElts = Mem->getNumValues() - 1;
+  auto ElementBitWidth = TotalWidth / NumElts;
+  assert(isPowerOf2_32(ElementBitWidth) && ElementBitWidth >= 8 &&
+         ElementBitWidth <= 128 && TotalWidth <= 256 &&
+         "Invalid width for load");
+  return ElementBitWidth;
+}
+
 bool NVPTXDAGToDAGISel::tryLDU(SDNode *N) {
   auto *LD = cast<MemSDNode>(N);
 
-  unsigned NumElts;
-  switch (N->getOpcode()) {
-  default:
-    llvm_unreachable("Unexpected opcode");
-  case ISD::INTRINSIC_W_CHAIN:
-    NumElts = 1;
-    break;
-  case NVPTXISD::LDUV2:
-    NumElts = 2;
-    break;
-  case NVPTXISD::LDUV4:
-    NumElts = 4;
-    break;
-  }
-
   SDLoc DL(N);
-  const unsigned FromTypeWidth = LD->getMemoryVT().getSizeInBits() / NumElts;
+  const unsigned FromTypeWidth = getFromTypeWidthForLoad(LD);
   const MVT::SimpleValueType TargetVT = LD->getSimpleValueType(0).SimpleTy;
 
   // If this is an LDU intrinsic, the address is the third operand. If its an
@@ -1443,7 +1424,7 @@ bool NVPTXDAGToDAGISel::tryStoreVector(SDNode *N) {
   // - for integer type, always use 'u'
   const unsigned TotalWidth = StoreVT.getSimpleVT().getSizeInBits();
 
-  const unsigned NumElts = getLoadStoreVectorNumElts(ST);
+  const unsigned NumElts = getStoreVectorNumElts(ST);
 
   SmallVector<SDValue, 16> Ops;
   for (auto &V : ST->ops().slice(1, NumElts))
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.h b/llvm/lib/Target/NVPTX/NVPTXISelDAGToDAG.h
@@ -111,6 +111,7 @@ class LLVM_LIBRARY_VISIBILITY NVPTXDAGToDAGISel : public SelectionDAGISel {
 
 public:
   static NVPTX::AddressSpace getAddrSpace(const MemSDNode *N);
+  static unsigned getFromTypeWidthForLoad(const MemSDNode *Mem);
 };
 
 class NVPTXDAGToDAGISelLegacy : public SelectionDAGISelLegacy {
diff --git a/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp b/llvm/lib/Target/NVPTX/NVPTXISelLowering.cpp
@@ -14,6 +14,7 @@
 #include "NVPTXISelLowering.h"
 #include "MCTargetDesc/NVPTXBaseInfo.h"
 #include "NVPTX.h"
+#include "NVPTXISelDAGToDAG.h"
 #include "NVPTXSubtarget.h"
 #include "NVPTXTargetMachine.h"
 #include "NVPTXTargetObjectFile.h"
@@ -5242,76 +5243,6 @@ static SDValue PerformFADDCombine(SDNode *N,
   return PerformFADDCombineWithOperands(N, N1, N0, DCI, OptLevel);
 }
 
-static SDValue PerformANDCombine(SDNode *N,
-                                 TargetLowering::DAGCombinerInfo &DCI) {
-  // The type legalizer turns a vector load of i8 values into a zextload to i16
-  // registers, optionally ANY_EXTENDs it (if target type is integer),
-  // and ANDs off the high 8 bits. Since we turn this load into a
-  // target-specific DAG node, the DAG combiner fails to eliminate these AND
-  // nodes. Do that here.
-  SDValue Val = N->getOperand(0);
-  SDValue Mask = N->getOperand(1);
-
-  if (isa<ConstantSDNode>(Val)) {
-    std::swap(Val, Mask);
-  }
-
-  SDValue AExt;
-
-  // Generally, we will see zextload -> IMOV16rr -> ANY_EXTEND -> and
-  if (Val.getOpcode() == ISD::ANY_EXTEND) {
-    AExt = Val;
-    Val = Val->getOperand(0);
-  }
-
-  if (Val->getOpcode() == NVPTXISD::LoadV2 ||
-      Val->getOpcode() == NVPTXISD::LoadV4) {
-    ConstantSDNode *MaskCnst = dyn_cast<ConstantSDNode>(Mask);
-    if (!MaskCnst) {
-      // Not an AND with a constant
-      return SDValue();
-    }
-
-    uint64_t MaskVal = MaskCnst->getZExtValue();
-    if (MaskVal != 0xff) {
-      // Not an AND that chops off top 8 bits
-      return SDValue();
-    }
-
-    MemSDNode *Mem = dyn_cast<MemSDNode>(Val);
-    if (!Mem) {
-      // Not a MemSDNode?!?
-      return SDValue();
-    }
-
-    EVT MemVT = Mem->getMemoryVT();
-    if (MemVT != MVT::v2i8 && MemVT != MVT::v4i8) {
-      // We only handle the i8 case
-      return SDValue();
-    }
-
-    unsigned ExtType = Val->getConstantOperandVal(Val->getNumOperands() - 1);
-    if (ExtType == ISD::SEXTLOAD) {
-      // If for some reason the load is a sextload, the and is needed to zero
-      // out the high 8 bits
-      return SDValue();
-    }
-
-    bool AddTo = false;
-    if (AExt.getNode() != nullptr) {
-      // Re-insert the ext as a zext.
-      Val = DCI.DAG.getNode(ISD::ZERO_EXTEND, SDLoc(N),
-                            AExt.getValueType(), Val);
-      AddTo = true;
-    }
-
-    // If we get here, the AND is unnecessary.  Just replace it with the load
-    DCI.CombineTo(N, Val, AddTo);
-  }
-
-  return SDValue();
-}
-
 static SDValue PerformREMCombine(SDNode *N,
                                  TargetLowering::DAGCombinerInfo &DCI,
                                  CodeGenOptLevel OptLevel) {
@@ -5983,8 +5914,6 @@ SDValue NVPTXTargetLowering::PerformDAGCombine(SDNode *N,
     return PerformADDCombine(N, DCI, OptLevel);
   case ISD::ADDRSPACECAST:
     return combineADDRSPACECAST(N, DCI);
-  case ISD::AND:
-    return PerformANDCombine(N, DCI);
   case ISD::SIGN_EXTEND:
   case ISD::ZERO_EXTEND:
     return combineMulWide(N, DCI, OptLevel);
@@ -6609,6 +6538,24 @@ static void computeKnownBitsForPRMT(const SDValue Op, KnownBits &Known,
   }
 }
 
+static void computeKnownBitsForLoadV(const SDValue Op, KnownBits &Known) {
+  MemSDNode *LD = cast<MemSDNode>(Op);
+
+  // We can't do anything without knowing the sign bit.
+  auto ExtType = LD->getConstantOperandVal(LD->getNumOperands() - 1);
+  if (ExtType == ISD::SEXTLOAD)
+    return;
+
+  // ExtLoading to vector types is weird and may not work well with known bits.
+  auto DestVT = LD->getValueType(0);
+  if (DestVT.isVector())
+    return;
+
+  assert(Known.getBitWidth() == DestVT.getSizeInBits());
+  auto ElementBitWidth = NVPTXDAGToDAGISel::getFromTypeWidthForLoad(LD);
+  Known.Zero.setHighBits(Known.getBitWidth() - ElementBitWidth);
+}
+
 void NVPTXTargetLowering::computeKnownBitsForTargetNode(
     const SDValue Op, KnownBits &Known, const APInt &DemandedElts,
     const SelectionDAG &DAG, unsigned Depth) const {
@@ -6618,6 +6565,11 @@ void NVPTXTargetLowering::computeKnownBitsForTargetNode(
   case NVPTXISD::PRMT:
     computeKnownBitsForPRMT(Op, Known, DAG, Depth);
     break;
+  case NVPTXISD::LoadV2:
+  case NVPTXISD::LoadV4:
+  case NVPTXISD::LoadV8:
+    computeKnownBitsForLoadV(Op, Known);
+    break;
   default:
     break;
   }
diff --git a/llvm/test/CodeGen/NVPTX/i8x2-instructions.ll b/llvm/test/CodeGen/NVPTX/i8x2-instructions.ll
@@ -103,5 +103,34 @@ define <2 x i8> @test_call_2xi8(<2 x i8> %a) {
   %res = call <2 x i8> @test_call_2xi8(<2 x i8> %a)
   ret <2 x i8> %res
 }
+
+define <2 x float> @test_uitofp_2xi8(<2 x i8> %a) {
+; O0-LABEL: test_uitofp_2xi8(
+; O0:       {
+; O0-NEXT:    .reg .b16 %rs<3>;
+; O0-NEXT:    .reg .b32 %r<4>;
+; O0-EMPTY:
+; O0-NEXT:  // %bb.0:
+; O0-NEXT:    ld.param.v2.b8 {%rs1, %rs2}, [test_uitofp_2xi8_param_0];
+; O0-NEXT:    mov.b32 %r1, {%rs1, %rs2};
+; O0-NEXT:    cvt.rn.f32.u16 %r2, %rs2;
+; O0-NEXT:    cvt.rn.f32.u16 %r3, %rs1;
+; O0-NEXT:    st.param.v2.b32 [func_retval0], {%r3, %r2};
+; O0-NEXT:    ret;
+;
+; O3-LABEL: test_uitofp_2xi8(
+; O3:       {
+; O3-NEXT:    .reg .b16 %rs<3>;
+; O3-NEXT:    .reg .b32 %r<3>;
+; O3-EMPTY:
+; O3-NEXT:  // %bb.0:
+; O3-NEXT:    ld.param.v2.b8 {%rs1, %rs2}, [test_uitofp_2xi8_param_0];
+; O3-NEXT:    cvt.rn.f32.u16 %r1, %rs2;
+; O3-NEXT:    cvt.rn.f32.u16 %r2, %rs1;
+; O3-NEXT:    st.param.v2.b32 [func_retval0], {%r2, %r1};
+; O3-NEXT:    ret;
+  %1 = uitofp <2 x i8> %a to <2 x float>
+  ret <2 x float> %1
+}
 ;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
 ; COMMON: {{.*}}
diff --git a/llvm/test/CodeGen/NVPTX/shift-opt.ll b/llvm/test/CodeGen/NVPTX/shift-opt.ll
@@ -71,18 +71,17 @@ define <2 x i16> @test_vec(<2 x i16> %x, <2 x i8> %y) {
 ; CHECK-LABEL: test_vec(
 ; CHECK:       {
 ; CHECK-NEXT:    .reg .b16 %rs<7>;
-; CHECK-NEXT:    .reg .b32 %r<5>;
+; CHECK-NEXT:    .reg .b32 %r<4>;
 ; CHECK-EMPTY:
 ; CHECK-NEXT:  // %bb.0:
 ; CHECK-NEXT:    ld.param.v2.b16 {%rs1, %rs2}, [test_vec_param_0];
 ; CHECK-NEXT:    ld.param.v2.b8 {%rs3, %rs4}, [test_vec_param_1];
 ; CHECK-NEXT:    mov.b32 %r1, {%rs3, %rs4};
-; CHECK-NEXT:    and.b32 %r2, %r1, 16711935;
 ; CHECK-NEXT:    shr.u16 %rs5, %rs2, 5;
 ; CHECK-NEXT:    shr.u16 %rs6, %rs1, 5;
-; CHECK-NEXT:    mov.b32 %r3, {%rs6, %rs5};
-; CHECK-NEXT:    or.b32 %r4, %r3, %r2;
-; CHECK-NEXT:    st.param.b32 [func_retval0], %r4;
+; CHECK-NEXT:    mov.b32 %r2, {%rs6, %rs5};
+; CHECK-NEXT:    or.b32 %r3, %r2, %r1;
+; CHECK-NEXT:    st.param.b32 [func_retval0], %r3;
 ; CHECK-NEXT:    ret;
   %ext = zext <2 x i8> %y to <2 x i16>
   %shl = shl <2 x i16> %ext, splat(i16 5)
