[ARM][MVE] Add DoubleWidthResult flag

Add a flag for those instructions which read from the top/bottom
halves of their inputs and produce a vector of results with double
width elements.

Differential Revision: https://reviews.llvm.org/D76762

Author: sparker-arm

llvm/lib/Target/ARM/ARMInstrFormats.td

@@ -410,6 +410,7 @@ class InstTemplate<AddrMode am, int sz, IndexMode im,
   bit validForTailPredication = 0;
   bit retainsPreviousHalfElement = 0;
   bit horizontalReduction = 0;
+  bit doubleWidthResult = 0;
 
   // If this is a pseudo instruction, mark it isCodeGenOnly.
   let isCodeGenOnly = !eq(!cast<string>(f), "Pseudo");
@@ -425,6 +426,7 @@ class InstTemplate<AddrMode am, int sz, IndexMode im,
   let TSFlags{20}    = validForTailPredication;
   let TSFlags{21}    = retainsPreviousHalfElement;
   let TSFlags{22}    = horizontalReduction;
+  let TSFlags{23}    = doubleWidthResult;
 
   let Constraints = cstr;
   let Itinerary = itin;

llvm/lib/Target/ARM/ARMInstrMVE.td

@@ -2513,6 +2513,7 @@ class MVE_VMOVL<string iname, string suffix, bits<2> sz, bit U, bit top,
   let Inst{11-6} = 0b111101;
   let Inst{4} = 0b0;
   let Inst{0} = 0b0;
+  let doubleWidthResult = 1;
 }
 
 multiclass MVE_VMOVL_m<bit top, string chr, MVEVectorVTInfo OutVTI,
@@ -2580,6 +2581,8 @@ class MVE_VSHLL_imm<string iname, string suffix, bit U, bit th,
 
   // For the MVE_VSHLL_patterns multiclass to refer to
   Operand immediateType = immtype;
+
+  let doubleWidthResult = 1;
 }
 
 // The immediate VSHLL instructions accept shift counts from 1 up to
@@ -2623,6 +2626,7 @@ class MVE_VSHLL_by_lane_width<string iname, string suffix, bits<2> size,
   let Inst{11-6} = 0b111000;
   let Inst{4} = 0b0;
   let Inst{0} = 0b1;
+  let doubleWidthResult = 1;
 }
 
 multiclass MVE_VSHLL_lw<string iname, string suffix, bits<2> sz, bit U,
@@ -4357,6 +4361,7 @@ class MVE_VMULL<string iname, string suffix, bit bit_28, bits<2> bits_21_20,
   let Inst{7} = Qn{3};
   let Inst{0} = 0b0;
   let validForTailPredication = 1;
+  let doubleWidthResult = 1;
 }
 
 multiclass MVE_VMULL_m<MVEVectorVTInfo VTI,
@@ -4731,6 +4736,7 @@ class MVE_VQDMULL<string iname, string suffix, bit size, bit T,
   let Inst{7} = Qn{3};
   let Inst{0} = 0b1;
   let validForTailPredication = 1;
+  let doubleWidthResult = 1;
 }
 
 multiclass MVE_VQDMULL_m<string iname, MVEVectorVTInfo VTI, bit size, bit T,
@@ -4937,6 +4943,7 @@ class MVE_VQDMULL_qr<string iname, string suffix, bit size,
   let Inst{8} = 0b1;
   let Inst{5} = 0b1;
   let validForTailPredication = 1;
+  let doubleWidthResult = 1;
 }
 
 multiclass MVE_VQDMULL_qr_m<string iname, MVEVectorVTInfo VTI, bit size,

llvm/lib/Target/ARM/MCTargetDesc/ARMBaseInfo.h

@@ -403,6 +403,10 @@ namespace ARMII {
     // Whether the instruction produces a scalar result from vector operands.
     HorizontalReduction = 1 << 22,
 
+    // Whether this instruction produces a vector result that is larger than
+    // its input, typically reading from the top/bottom halves of the input(s).
+    DoubleWidthResult = 1 << 23,
+
     //===------------------------------------------------------------------===//
     // Code ___domain.
     DomainShift   = 15,

llvm/unittests/Target/ARM/MachineInstrTest.cpp

@@ -10,6 +10,103 @@
 
 using namespace llvm;
 
+TEST(MachineInstructionDoubleWidthResult, IsCorrect) {
+  using namespace ARM;
+
+  auto DoubleWidthResult = [](unsigned Opcode) {
+    switch (Opcode) {
+    default:
+      break;
+    case MVE_VMULLBp16:
+    case MVE_VMULLBp8:
+    case MVE_VMULLBs16:
+    case MVE_VMULLBs32:
+    case MVE_VMULLBs8:
+    case MVE_VMULLBu16:
+    case MVE_VMULLBu32:
+    case MVE_VMULLBu8:
+    case MVE_VMULLTp16:
+    case MVE_VMULLTp8:
+    case MVE_VMULLTs16:
+    case MVE_VMULLTs32:
+    case MVE_VMULLTs8:
+    case MVE_VMULLTu16:
+    case MVE_VMULLTu32:
+    case MVE_VMULLTu8:
+    case MVE_VQDMULL_qr_s16bh:
+    case MVE_VQDMULL_qr_s16th:
+    case MVE_VQDMULL_qr_s32bh:
+    case MVE_VQDMULL_qr_s32th:
+    case MVE_VQDMULLs16bh:
+    case MVE_VQDMULLs16th:
+    case MVE_VQDMULLs32bh:
+    case MVE_VQDMULLs32th:
+    case MVE_VMOVLs16bh:
+    case MVE_VMOVLs16th:
+    case MVE_VMOVLs8bh:
+    case MVE_VMOVLs8th:
+    case MVE_VMOVLu16bh:
+    case MVE_VMOVLu16th:
+    case MVE_VMOVLu8bh:
+    case MVE_VMOVLu8th:
+    case MVE_VSHLL_imms16bh:
+    case MVE_VSHLL_imms16th:
+    case MVE_VSHLL_imms8bh:
+    case MVE_VSHLL_imms8th:
+    case MVE_VSHLL_immu16bh:
+    case MVE_VSHLL_immu16th:
+    case MVE_VSHLL_immu8bh:
+    case MVE_VSHLL_immu8th:
+    case MVE_VSHLL_lws16bh:
+    case MVE_VSHLL_lws16th:
+    case MVE_VSHLL_lws8bh:
+    case MVE_VSHLL_lws8th:
+    case MVE_VSHLL_lwu16bh:
+    case MVE_VSHLL_lwu16th:
+    case MVE_VSHLL_lwu8bh:
+    case MVE_VSHLL_lwu8th:
+      return true;
+    }
+    return false;
+  };
+
+  LLVMInitializeARMTargetInfo();
+  LLVMInitializeARMTarget();
+  LLVMInitializeARMTargetMC();
+
+  auto TT(Triple::normalize("thumbv8.1m.main-arm-none-eabi"));
+  std::string Error;
+  const Target *T = TargetRegistry::lookupTarget(TT, Error);
+  if (!T) {
+    dbgs() << Error;
+    return;
+  }
+
+  TargetOptions Options;
+  auto TM = std::unique_ptr<LLVMTargetMachine>(
+    static_cast<LLVMTargetMachine*>(
+      T->createTargetMachine(TT, "generic", "", Options, None, None,
+                             CodeGenOpt::Default)));
+  ARMSubtarget ST(TM->getTargetTriple(), std::string(TM->getTargetCPU()),
+                  std::string(TM->getTargetFeatureString()),
+                  *static_cast<const ARMBaseTargetMachine *>(TM.get()), false);
+  const ARMBaseInstrInfo *TII = ST.getInstrInfo();
+  auto MII = TM->getMCInstrInfo();
+
+  for (unsigned i = 0; i < ARM::INSTRUCTION_LIST_END; ++i) {
+    const MCInstrDesc &Desc = TII->get(i);
+
+    uint64_t Flags = Desc.TSFlags;
+    if ((Flags & ARMII::DomainMask) != ARMII::DomainMVE)
+      continue;
+
+    bool Valid = (Flags & ARMII::DoubleWidthResult) != 0;
+    ASSERT_EQ(DoubleWidthResult(i), Valid)
+              << MII->getName(i)
+              << ": mismatched expectation for tail-predicated safety\n";
+  }
+}
+
 TEST(MachineInstructionHorizontalReduction, IsCorrect) {
   using namespace ARM;
 
@@ -159,7 +256,6 @@ TEST(MachineInstructionHorizontalReduction, IsCorrect) {
     uint64_t Flags = Desc.TSFlags;
     if ((Flags & ARMII::DomainMask) != ARMII::DomainMVE)
       continue;
-
     bool Valid = (Flags & ARMII::HorizontalReduction) != 0;
     ASSERT_EQ(HorizontalReduction(i), Valid)
               << MII->getName(i)