From d89b55e3097078fb05edb0336178294d507ce2a8 Mon Sep 17 00:00:00 2001
From: Alex Lorenz <arphaman@gmail.com>
Date: Wed, 24 Jun 2015 17:34:58 +0000
Subject: [PATCH] MIR Serialization: Serialize the null register operands.

This commit serializes the null register machine operands.
It uses the '_' keyword to represent them, but the parser
also allows the '%noreg' named register syntax.

Reviewers: Duncan P. N. Exon Smith

Differential Revision: http://reviews.llvm.org/D10580


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240558 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/MIRParser/MILexer.cpp             |  4 +++-
 lib/CodeGen/MIRParser/MILexer.h               |  5 +++-
 lib/CodeGen/MIRParser/MIParser.cpp            |  6 +++++
 lib/CodeGen/MIRPrinter.cpp                    |  5 ++--
 .../MIR/X86/null-register-operands.mir        | 23 +++++++++++++++++++
 5 files changed, 39 insertions(+), 4 deletions(-)
 create mode 100644 test/CodeGen/MIR/X86/null-register-operands.mir

diff --git a/lib/CodeGen/MIRParser/MILexer.cpp b/lib/CodeGen/MIRParser/MILexer.cpp
index 0933ae138f2..3383d1f5cf5 100644
--- a/lib/CodeGen/MIRParser/MILexer.cpp
+++ b/lib/CodeGen/MIRParser/MILexer.cpp
@@ -64,7 +64,9 @@ static Cursor lexIdentifier(Cursor C, MIToken &Token) {
   auto Range = C;
   while (isIdentifierChar(C.peek()))
     C.advance();
-  Token = MIToken(MIToken::Identifier, Range.upto(C));
+  auto Identifier = Range.upto(C);
+  Token = MIToken(Identifier == "_" ? MIToken::underscore : MIToken::Identifier,
+                  Identifier);
   return C;
 }
 
diff --git a/lib/CodeGen/MIRParser/MILexer.h b/lib/CodeGen/MIRParser/MILexer.h
index df8b6cb2026..f9cc97cb34e 100644
--- a/lib/CodeGen/MIRParser/MILexer.h
+++ b/lib/CodeGen/MIRParser/MILexer.h
@@ -34,6 +34,7 @@ struct MIToken {
     // Tokens with no info.
     comma,
     equal,
+    underscore,
 
     // Identifier tokens
     Identifier,
@@ -58,7 +59,9 @@ public:
 
   bool isError() const { return Kind == Error; }
 
-  bool isRegister() const { return Kind == NamedRegister; }
+  bool isRegister() const {
+    return Kind == NamedRegister || Kind == underscore;
+  }
 
   bool is(TokenKind K) const { return Kind == K; }
 
diff --git a/lib/CodeGen/MIRParser/MIParser.cpp b/lib/CodeGen/MIRParser/MIParser.cpp
index 33f306945cb..07aac674ffb 100644
--- a/lib/CodeGen/MIRParser/MIParser.cpp
+++ b/lib/CodeGen/MIRParser/MIParser.cpp
@@ -174,6 +174,9 @@ bool MIParser::parseInstruction(unsigned &OpCode) {
 
 bool MIParser::parseRegister(unsigned &Reg) {
   switch (Token.kind()) {
+  case MIToken::underscore:
+    Reg = 0;
+    break;
   case MIToken::NamedRegister: {
     StringRef Name = Token.stringValue().drop_front(1); // Drop the '%'
     if (getRegisterByName(Name, Reg))
@@ -211,6 +214,7 @@ bool MIParser::parseImmediateOperand(MachineOperand &Dest) {
 
 bool MIParser::parseMachineOperand(MachineOperand &Dest) {
   switch (Token.kind()) {
+  case MIToken::underscore:
   case MIToken::NamedRegister:
     return parseRegisterOperand(Dest);
   case MIToken::IntegerLiteral:
@@ -245,6 +249,8 @@ bool MIParser::parseInstrName(StringRef InstrName, unsigned &OpCode) {
 void MIParser::initNames2Regs() {
   if (!Names2Regs.empty())
     return;
+  // The '%noreg' register is the register 0.
+  Names2Regs.insert(std::make_pair("noreg", 0));
   const auto *TRI = MF.getSubtarget().getRegisterInfo();
   assert(TRI && "Expected target register info");
   for (unsigned I = 0, E = TRI->getNumRegs(); I < E; ++I) {
diff --git a/lib/CodeGen/MIRPrinter.cpp b/lib/CodeGen/MIRPrinter.cpp
index 6d62b0ad85b..801f6c25ac5 100644
--- a/lib/CodeGen/MIRPrinter.cpp
+++ b/lib/CodeGen/MIRPrinter.cpp
@@ -144,9 +144,10 @@ void MIPrinter::print(const MachineInstr &MI) {
 static void printReg(unsigned Reg, raw_ostream &OS,
                      const TargetRegisterInfo *TRI) {
   // TODO: Print Stack Slots.
-  // TODO: Print no register.
   // TODO: Print virtual registers.
-  if (Reg < TRI->getNumRegs())
+  if (!Reg)
+    OS << '_';
+  else if (Reg < TRI->getNumRegs())
     OS << '%' << StringRef(TRI->getName(Reg)).lower();
   else
     llvm_unreachable("Can't print this kind of register yet");
diff --git a/test/CodeGen/MIR/X86/null-register-operands.mir b/test/CodeGen/MIR/X86/null-register-operands.mir
new file mode 100644
index 00000000000..7946649cfb1
--- /dev/null
+++ b/test/CodeGen/MIR/X86/null-register-operands.mir
@@ -0,0 +1,23 @@
+# RUN: llc -march=x86-64 -start-after branch-folder -stop-after branch-folder -o /dev/null %s | FileCheck %s
+# This test ensures that the MIR parser parses null register operands correctly.
+
+--- |
+
+  define i32 @deref(i32* %p) {
+  entry:
+    %a = load i32, i32* %p
+    ret i32 %a
+  }
+
+...
+---
+# CHECK: name: deref
+name:            deref
+body:
+ - name:         entry
+   instructions:
+     # CHECK:      - '%eax = MOV32rm %rdi, 1, _, 0, _'
+     # CHECK-NEXT: - 'RETQ %eax'
+     - '%eax = MOV32rm %rdi, 1, _, 0, %noreg'
+     - 'RETQ %eax'
+...