[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.

4 files changed, 36 insertions, 2 deletions

diff --git a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp
index 88d353e..709aa00 100644
--- a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.cpp
+++ b/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);
 }
diff --git a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
index 7f94db0..1f4d45d8 100644
--- a/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
+++ b/llvm/utils/TableGen/Common/CodeGenDAGPatterns.h
@@ -533,6 +533,8 @@ public:
 
   // 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;
diff --git a/llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.h b/llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.h
index 5fe3f9a..edddc05 100644
--- a/llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.h
+++ b/llvm/utils/TableGen/Common/GlobalISel/GlobalISelMatchTable.h
@@ -806,6 +806,7 @@ public:
     IPM_MemoryAlignment,
     IPM_VectorSplatImm,
     IPM_NoUse,
+    IPM_OneUse,
     IPM_GenericPredicate,
     IPM_MIFlags,
     OPM_SameOperand,
@@ -1691,6 +1692,28 @@ public:
   }
 };
 
+/// 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.
 ///
diff --git a/llvm/utils/TableGen/GlobalISelEmitter.cpp b/llvm/utils/TableGen/GlobalISelEmitter.cpp
index 9b35614..ec41cd9 100644
--- a/llvm/utils/TableGen/GlobalISelEmitter.cpp
+++ b/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()) {