[TableGen] HasOneUse builtin predicate on PatFrags (#91578)

This predicate tells GlobalISelEmitter and DAGISelEmitter to check that
the instruction to emit has only one use of its result. This can be used
on a PatFrag instead of defining custom predicates for both emitters per
record that requires it.

Author: jofrn

llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutor.h

@@ -212,6 +212,10 @@ enum {
   /// - InsnID(ULEB128) - Instruction ID
   GIM_CheckHasNoUse,
 
+  /// Check if there's one use of the first result.
+  /// - InsnID(ULEB128) - Instruction ID
+  GIM_CheckHasOneUse,
+
   /// Check the type for the specified operand
   /// - InsnID(ULEB128) - Instruction ID
   /// - OpIdx(ULEB128) - Operand index

llvm/include/llvm/CodeGen/GlobalISel/GIMatchTableExecutorImpl.h

@@ -468,7 +468,24 @@ bool GIMatchTableExecutor::executeMatchTable(
         if (handleReject() == RejectAndGiveUp)
           return false;
       }
+      break;
+    }
+    case GIM_CheckHasOneUse: {
+      uint64_t InsnID = readULEB();
+
+      DEBUG_WITH_TYPE(TgtExecutor::getName(),
+                      dbgs() << CurrentIdx << ": GIM_CheckHasOneUse(MIs["
+                             << InsnID << "]\n");
+
+      const MachineInstr *MI = State.MIs[InsnID];
+      assert(MI && "Used insn before defined");
+      assert(MI->getNumDefs() > 0 && "No defs");
+      const Register Res = MI->getOperand(0).getReg();
 
+      if (!MRI.hasOneNonDBGUse(Res)) {
+        if (handleReject() == RejectAndGiveUp)
+          return false;
+      }
       break;
     }
     case GIM_CheckAtomicOrdering: {

llvm/include/llvm/Target/TargetSelectionDAG.td

@@ -884,6 +884,9 @@ class PatFrags<dag ops, list<dag> frags, code pred = [{}],
   // If set to true, a predicate is added that checks for the absence of use of
   // the first result.
   bit HasNoUse = ?;
+  // If set to true, a predicate is added that checks for the sole use of
+  // the first result.
+  bit HasOneUse = ?;
 
   // Is the desired pre-packaged predicate for a load?
   bit IsLoad = ?;

llvm/test/TableGen/predicate-patfags.td

@@ -1,5 +1,7 @@
-// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include -I %p/Common %s 2>&1 | FileCheck -check-prefix=SDAG %s
-// RUN: llvm-tblgen -gen-global-isel -I %p/../../include -I %p/Common %s 2>&1 | FileCheck -check-prefix=GISEL %s
+// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include -I %p/Common %s 2>&1 | FileCheck -check-prefixes=SDAG,SCUSTOM %s
+// RUN: llvm-tblgen -gen-dag-isel -I %p/../../include -I %p/Common %s -DHASONEUSE 2>&1 | FileCheck -check-prefixes=SDAG,SBUILTIN %s
+// RUN: llvm-tblgen -gen-global-isel -I %p/../../include -I %p/Common %s 2>&1 | FileCheck -check-prefixes=GISEL,GCUSTOM %s
+// RUN: llvm-tblgen -gen-global-isel -I %p/../../include -I %p/Common %s -DHASONEUSE 2>&1 | FileCheck -check-prefixes=GISEL,GBUILTIN %s
 
 include "llvm/Target/Target.td"
 include "GlobalISelEmitterCommon.td"
@@ -31,11 +33,16 @@ def : GINodeEquiv<G_TGT_MUL24, TGTmul24_impl>;
 
 def TGTmul24_oneuse : PatFrag<
   (ops node:$src0, node:$src1),
-  (TGTmul24 $src0, $src1),
-  [{ return N->hasOneUse(); }]> {
+  (TGTmul24 $src0, $src1)
+#ifndef HASONEUSE
+  , [{ return N->hasOneUse(); }]> {
   let GISelPredicateCode = [{
     return MRI->hasOneNonDBGUse(MI.getOperand(0).getReg());
   }];
+#else
+  > {
+  let HasOneUse = 1;
+#endif
 }
 
 // SDAG: OPC_CheckOpcode, TARGET_VAL(ISD::INTRINSIC_W_CHAIN),
@@ -44,19 +51,26 @@ def TGTmul24_oneuse : PatFrag<
 // SDAG: OPC_CheckOpcode, TARGET_VAL(TargetISD::MUL24),
 // SDAG: OPC_CheckPredicate0, // Predicate_TGTmul24_oneuse
 
+// SCUSTOM: return N->hasOneUse();
+// SBUILTIN: if (!SDValue(N, 0).hasOneUse()) return false;
+
 // GISEL: GIM_CheckOpcode, /*MI*/1, GIMT_Encode2(TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS),
 // GISEL: GIM_CheckIntrinsicID, /*MI*/1, /*Op*/1, GIMT_Encode2(Intrinsic::tgt_mul24),
-// GISEL: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
+// GBUILTIN: GIM_CheckHasOneUse, /*MI*/1,
+// GCUSTOM: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
 
 // GISEL: GIM_CheckOpcode, /*MI*/1, GIMT_Encode2(TargetOpcode::G_INTRINSIC_W_SIDE_EFFECTS),
 // GISEL: GIM_CheckIntrinsicID, /*MI*/1, /*Op*/1, GIMT_Encode2(Intrinsic::tgt_mul24),
-// GISEL: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
+// GBUILTIN: GIM_CheckHasOneUse, /*MI*/1,
+// GCUSTOM: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
 
 // GISEL: GIM_CheckOpcode, /*MI*/1, GIMT_Encode2(MyTarget::G_TGT_MUL24),
-// GISEL: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
+// GBUILTIN: GIM_CheckHasOneUse, /*MI*/1,
+// GCUSTOM: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
 
 // GISEL: GIM_CheckOpcode, /*MI*/1, GIMT_Encode2(MyTarget::G_TGT_MUL24),
-// GISEL: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
+// GBUILTIN: GIM_CheckHasOneUse, /*MI*/1,
+// GCUSTOM: GIM_CheckCxxInsnPredicate, /*MI*/1, /*FnId*/GIMT_Encode2(GICXXPred_MI_Predicate_TGTmul24_oneuse),
 def inst_mad24 : I<
   (outs GPR32:$dst),
   (ins GPR32:$src0, GPR32:$src1, GPR32:$src2),

llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp

@@ -903,7 +903,7 @@ TreePredicateFn::TreePredicateFn(TreePattern *N) : PatFragRec(N) {
 }
 
 bool TreePredicateFn::hasPredCode() const {
-  return isLoad() || isStore() || isAtomic() || hasNoUse() ||
+  return isLoad() || isStore() || isAtomic() || hasNoUse() || hasOneUse() ||
          !PatFragRec->getRecord()->getValueAsString("PredicateCode").empty();
 }
 
@@ -1140,6 +1140,8 @@ std::string TreePredicateFn::getPredCode() const {
 
   if (hasNoUse())
     Code += "if (!SDValue(N, 0).use_empty()) return false;\n";
+  if (hasOneUse())
+    Code += "if (!SDValue(N, 0).hasOneUse()) return false;\n";
 
   std::string PredicateCode =
       std::string(PatFragRec->getRecord()->getValueAsString("PredicateCode"));
@@ -1187,6 +1189,9 @@ bool TreePredicateFn::usesOperands() const {
 bool TreePredicateFn::hasNoUse() const {
   return isPredefinedPredicateEqualTo("HasNoUse", true);
 }
+bool TreePredicateFn::hasOneUse() const {
+  return isPredefinedPredicateEqualTo("HasOneUse", true);
+}
 bool TreePredicateFn::isLoad() const {
   return isPredefinedPredicateEqualTo("IsLoad", true);
 }

llvm/utils/TableGen/Common/CodeGenDAGPatterns.h

@@ -533,6 +533,8 @@ class TreePredicateFn {
 
   // Check if the HasNoUse predicate is set.
   bool hasNoUse() const;
+  // Check if the HasOneUse predicate is set.
+  bool hasOneUse() const;
 
   // Is the desired predefined predicate for a load?
   bool isLoad() const;

llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.h

@@ -806,6 +806,7 @@ class PredicateMatcher {
     IPM_MemoryAlignment,
     IPM_VectorSplatImm,
     IPM_NoUse,
+    IPM_OneUse,
     IPM_GenericPredicate,
     IPM_MIFlags,
     OPM_SameOperand,
@@ -1691,6 +1692,28 @@ class NoUsePredicateMatcher : public InstructionPredicateMatcher {
   }
 };
 
+/// Generates code to check that the first result has only one use.
+class OneUsePredicateMatcher : public InstructionPredicateMatcher {
+public:
+  OneUsePredicateMatcher(unsigned InsnVarID)
+      : InstructionPredicateMatcher(IPM_OneUse, InsnVarID) {}
+
+  static bool classof(const PredicateMatcher *P) {
+    return P->getKind() == IPM_OneUse;
+  }
+
+  bool isIdentical(const PredicateMatcher &B) const override {
+    return InstructionPredicateMatcher::isIdentical(B);
+  }
+
+  void emitPredicateOpcodes(MatchTable &Table,
+                            RuleMatcher &Rule) const override {
+    Table << MatchTable::Opcode("GIM_CheckHasOneUse")
+          << MatchTable::Comment("MI") << MatchTable::ULEB128Value(InsnVarID)
+          << MatchTable::LineBreak;
+  }
+};
+
 /// Generates code to check that a set of predicates and operands match for a
 /// particular instruction.
 ///

llvm/utils/TableGen/GlobalISelEmitter.cpp

@@ -207,7 +207,7 @@ static Error isTrivialOperatorNode(const TreePatternNode &N) {
     if (Predicate.isImmediatePattern())
       continue;
 
-    if (Predicate.hasNoUse())
+    if (Predicate.hasNoUse() || Predicate.hasOneUse())
       continue;
 
     if (Predicate.isNonExtLoad() || Predicate.isAnyExtLoad() ||
@@ -782,6 +782,10 @@ Expected<InstructionMatcher &> GlobalISelEmitter::createAndImportSelDAGMatcher(
       InsnMatcher.addPredicate<NoUsePredicateMatcher>();
       HasAddedBuiltinMatcher = true;
     }
+    if (Predicate.hasOneUse()) {
+      InsnMatcher.addPredicate<OneUsePredicateMatcher>();
+      HasAddedBuiltinMatcher = true;
+    }
 
     if (Predicate.hasGISelPredicateCode()) {
       if (Predicate.usesOperands()) {