Split pseudo-instruction expansion into a separate pass, to make it

easier to debug, and to avoid complications when the CFG changes
in the middle of the instruction selection process.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119382 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/ExpandPseudos.cpp

@@ -0,0 +1,84 @@
+//===-- llvm/CodeGen/ExpandPseudos.cpp --------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Expand Psuedo-instructions produced by ISel. These is usually to allow
+// the expansion to contain control flow, such as a conditional move
+// implemented with a conditional branch and a phi, or an atomic operation
+// implemented with a loop.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "expand-pseudos"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Target/TargetLowering.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/Debug.h"
+using namespace llvm;
+
+namespace {
+  class ExpandPseudos : public MachineFunctionPass {
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    ExpandPseudos() : MachineFunctionPass(ID) {}
+
+  private:
+    virtual bool runOnMachineFunction(MachineFunction &MF);
+
+    const char *getPassName() const {
+      return "Expand CodeGen Pseudo-instructions";
+    }
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+  };
+} // end anonymous namespace
+
+char ExpandPseudos::ID = 0;
+INITIALIZE_PASS_BEGIN(ExpandPseudos, "expand-pseudos",
+                "Expand CodeGen Psueod-instructions", false, false)
+INITIALIZE_PASS_END(ExpandPseudos, "expand-pseudos",
+                "Expand CodeGen Psueod-instructions", false, false)
+
+FunctionPass *llvm::createExpandPseudosPass() {
+  return new ExpandPseudos();
+}
+
+bool ExpandPseudos::runOnMachineFunction(MachineFunction &MF) {
+  bool Changed = false;
+  const TargetLowering *TLI = MF.getTarget().getTargetLowering();
+
+  // Iterate through each instruction in the function, looking for pseudos.
+  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
+    MachineBasicBlock *MBB = I;
+    for (MachineBasicBlock::iterator MBBI = MBB->begin(), MBBE = MBB->end();
+         MBBI != MBBE; ) {
+      MachineInstr *MI = MBBI++;
+
+      // If MI is a pseudo, expand it.
+      const TargetInstrDesc &TID = MI->getDesc();
+      if (TID.usesCustomInsertionHook()) {
+        Changed = true;
+        MachineBasicBlock *NewMBB =
+          TLI->EmitInstrWithCustomInserter(MI, MBB);
+        // The expansion may involve new basic blocks.
+        if (NewMBB != MBB) {
+          MBB = NewMBB;
+          I = NewMBB;
+          MBBI = NewMBB->begin();
+          MBBE = NewMBB->end();
+        }
+      }
+    }
+  }
+
+  return Changed;
+}