From 2ecff3bff26c6481bf526d68ef927433474ccac7 Mon Sep 17 00:00:00 2001
From: Quentin Colombet <qcolombet@apple.com>
Date: Wed, 10 Feb 2016 22:59:27 +0000
Subject: [PATCH] [GlobalISel] More detailed skeleton for the IRTranslator.

llvm-svn: 260456
---
 .../include/llvm/CodeGen/GlobalISel/IRTranslator.h | 26 ++++++++---------
 llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp       | 33 ++++++++++++++++++++--
 2 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h b/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
index c201afd..75e14cf 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/IRTranslator.h
@@ -20,6 +20,7 @@
 #define LLVM_CODEGEN_GLOBALISEL_IRTRANSLATOR_H
 
 #include "Types.h"
+#include "llvm/ADT/SetVector.h"
 #include "llvm/CodeGen/MachineFunctionPass.h"
 #include "llvm/IR/Constants.h"
 
@@ -52,17 +53,15 @@ private:
   // registers, but we would need to encapsulate that in a higher
   // level class.
   ValueToVRegs ValToVRegs;
-  // Mapping of a constant to the instructions to produce
-  // that constant.
   // Constants are special because when we encounter one,
   // we do not know at first where to insert the definition since
   // this depends on all its uses.
   // Thus, we will insert the sequences to materialize them when
   // we know all their users.
-  // In the meantime, just keep it in a map.
+  // In the meantime, just keep it in a set.
   // Note: Constants that end up as immediate in the related instructions,
   // do not appear in that map.
-  DenseMap<const Constant *, SmallVector<MachineInstr *, 1>> ConstantToSequence;
+  SmallSetVector<const Constant *, 8> Constants;
 
   /* A bunch of methods targeting ADD, SUB, etc. */
   // Return true if the translation was successful, false
@@ -76,8 +75,14 @@ private:
   // 2 Update the ValToVReg accordingly.
   // 2.alt. For constant arguments, if they are compile time constants,
   //   produce an immediate in the right operand and do not touch
-  //   ValToReg. Otherwise, update ValToVReg and register the
-  //   sequence to materialize the constant in ConstantToSequence.
+  //   ValToReg. Actually we will go with a virtual register for each
+  //   constants because it may be expensive to actually materialize the
+  //   constant. Moreover, if the constant spans on several instructions,
+  //   CSE may not catch them.
+  //   => Update ValToVReg and remember that we saw a constant in Constants.
+  //   We will materialize all the constants in finalize.
+  // Note: we would need to do something so that we can recognize such operand
+  //       as constants.
   // 3. Create the generic instruction.
   bool translateADD(const Instruction &Inst);
 
@@ -94,20 +99,13 @@ private:
 
   // * Insert all the code needed to materialize the constants
   // at the proper place. E.g., Entry block or dominator block
-  // of each constant depending ob how fancy we want to be.
+  // of each constant depending on how fancy we want to be.
   // * Clear the different maps.
   void finalize();
 public:
   // Ctor, nothing fancy.
   IRTranslator();
 
-  // Instead of having the instance of the IRTranslatorToolkit
-  // as an argument of the constructor of IRTranslator, we ask
-  // the target the instance of the toolkit for each MachineFunction.
-  // The interest is that we may have different translator for different
-  // subtract or optimization. E.g., we could have a translator optimized
-  // to produce small code size.
-  //
   // Algo:
   //   CallLowering = MF.subtarget.getCallLowering()
   //   F = MF.getParent()
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index efb4ead..704b019 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -12,20 +12,39 @@
 
 #include "llvm/CodeGen/GlobalISel/IRTranslator.h"
 
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/IR/Function.h"
+
+#define DEBUG_TYPE "irtranslator"
+
 using namespace llvm;
 
 char IRTranslator::ID = 0;
 
 bool IRTranslator::translateADD(const Instruction &Inst) {
+  // Get or create a virtual register for each value.
+  // Unless the value is a Constant => loadimm cst?
+  // or inline constant each time?
+  // Creation of a virtual register needs to have a size.
   return false;
 }
 
-bool IRTranslator::translate(const Instruction &) {
-  return false;
+bool IRTranslator::translate(const Instruction &Inst) {
+  switch(Inst.getOpcode()) {
+    case Instruction::Add: {
+      return translateADD(Inst);
+    default:
+      llvm_unreachable("Opcode not supported");
+    }
+  }
 }
 
 
 void IRTranslator::finalize() {
+  // Release the memory used by the different maps we
+  // needed during the translation.
+  ValToVRegs.clear();
+  Constants.clear();
 }
 
 IRTranslator::IRTranslator()
@@ -33,5 +52,15 @@ IRTranslator::IRTranslator()
 }
 
 bool IRTranslator::runOnMachineFunction(MachineFunction &MF) {
+  const Function &F = *MF.getFunction();
+  for (const BasicBlock &BB: F) {
+    for (const Instruction &Inst: BB) {
+      bool Succeeded = translate(Inst);
+      if (!Succeeded) {
+        DEBUG(dbgs() << "Cannot translate: " << Inst << '\n');
+        report_fatal_error("Unable to translate instruction");
+      }
+    }
+  }
   return false;
 }
-- 
2.7.4