Record the ad hoc aliasing graph in CodeGenRegister.

The ad hoc aliasing specified in the 'Aliases' list in .td files is
currently only used by computeOverlaps(). It will soon be needed to
build accurate register units as well, so build the undirected graph in
CodeGenRegister::buildObjectGraph() instead.

Aliasing is a symmetric relationship with only one direction specified
in the .td files. Make sure both directions are represented in
getExplicitAliases().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156762 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 21 insertions, 5 deletions

diff --git a/utils/TableGen/CodeGenRegisters.cpp b/utils/TableGen/CodeGenRegisters.cpp
index 499292a196..797c31a934 100644
--- a/utils/TableGen/CodeGenRegisters.cpp
+++ b/utils/TableGen/CodeGenRegisters.cpp
@@ -108,6 +108,15 @@ void CodeGenRegister::buildObjectGraph(CodeGenRegBank &RegBank) {
   // This is used by computeSecondarySubRegs() to find candidates.
   if (CoveredBySubRegs && !ExplicitSubRegs.empty())
     ExplicitSubRegs.front()->LeadingSuperRegs.push_back(this);
+
+  // Add ad hoc alias links. This is a symmetric relationship betwen two
+  // registers, so build a symmetric graph by adding links in both ends.
+  std::vector<Record*> Aliases = TheDef->getValueAsListOfDefs("Aliases");
+  for (unsigned i = 0, e = Aliases.size(); i != e; ++i) {
+    CodeGenRegister *Reg = RegBank.getReg(Aliases[i]);
+    ExplicitAliases.push_back(Reg);
+    Reg->ExplicitAliases.push_back(this);
+  }
 }
 
 const std::string &CodeGenRegister::getName() const {
@@ -1529,16 +1538,13 @@ computeOverlaps(std::map<const CodeGenRegister*, CodeGenRegister::Set> &Map) {
     Overlaps.insert(Supers.begin(), Supers.end());
 
     // Form symmetrical relations from the special Aliases[] lists.
-    std::vector<Record*> RegList = Reg->TheDef->getValueAsListOfDefs("Aliases");
+    ArrayRef<CodeGenRegister*> RegList = Reg->getExplicitAliases();
     for (unsigned i2 = 0, e2 = RegList.size(); i2 != e2; ++i2) {
-      CodeGenRegister *Reg2 = getReg(RegList[i2]);
-      CodeGenRegister::Set &Overlaps2 = Map[Reg2];
+      CodeGenRegister *Reg2 = RegList[i2];
       const CodeGenRegister::SuperRegList &Supers2 = Reg2->getSuperRegs();
       // Reg overlaps Reg2 which implies it overlaps supers(Reg2).
       Overlaps.insert(Reg2);
       Overlaps.insert(Supers2.begin(), Supers2.end());
-      Overlaps2.insert(Reg);
-      Overlaps2.insert(Supers.begin(), Supers.end());
     }
   }
 
diff --git a/utils/TableGen/CodeGenRegisters.h b/utils/TableGen/CodeGenRegisters.h
index 7e2c07ee58..491a91667a 100644
--- a/utils/TableGen/CodeGenRegisters.h
+++ b/utils/TableGen/CodeGenRegisters.h
@@ -142,6 +142,13 @@ namespace llvm {
       return SuperRegs;
     }
 
+    // Get the list of ad hoc aliases. The graph is symmetric, so the list
+    // contains all registers in 'Aliases', and all registers that mention this
+    // register in 'Aliases'.
+    ArrayRef<CodeGenRegister*> getExplicitAliases() const {
+      return ExplicitAliases;
+    }
+
     // Get the topological signature of this register. This is a small integer
     // less than RegBank.getNumTopoSigs(). Registers with the same TopoSig have
     // identical sub-register structure. That is, they support the same set of
@@ -191,6 +198,9 @@ namespace llvm {
     SmallVector<CodeGenSubRegIndex*, 8> ExplicitSubRegIndices;
     SmallVector<CodeGenRegister*, 8> ExplicitSubRegs;
 
+    // Explicit ad hoc aliases, symmetrized to form an undirected graph.
+    SmallVector<CodeGenRegister*, 8> ExplicitAliases;
+
     // Super-registers where this is the first explicit sub-register.
     SuperRegList LeadingSuperRegs;