Add support for a pattern matching instruction selector. This is still in

the early implementation phases, so it is disabled by default


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7719 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 117 insertions, 0 deletions

diff --git a/lib/Target/X86/InstSelectPattern.cpp b/lib/Target/X86/InstSelectPattern.cpp
new file mode 100644
index 0000000000..4b9e381ec1
--- /dev/null
+++ b/lib/Target/X86/InstSelectPattern.cpp
@@ -0,0 +1,117 @@
+//===-- InstSelectPattern.cpp - A pattern matching inst selector for X86 --===//
+//
+// This file defines a pattern matching instruction selector for X86.
+//
+//  FIXME: we could allocate one big array of unsigneds to use as the backing
+//         store for all of the nodes costs arrays.
+//
+//===----------------------------------------------------------------------===//
+
+#include "X86.h"
+#include "llvm/Pass.h"
+#include "llvm/Function.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/CodeGen/SelectionDAG.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/SSARegMap.h"
+
+#include "X86RegisterInfo.h"
+
+// Include the generated instruction selector...
+#include "X86GenInstrSelector.inc"
+
+
+//===----------------------------------------------------------------------===//
+//  User code
+//
+
+
+namespace {
+  struct ISel : public FunctionPass, SelectionDAGTargetBuilder {
+    TargetMachine &TM;
+    ISel(TargetMachine &tm) : TM(tm) {}
+    int VarArgsFrameIndex;              // FrameIndex for start of varargs area
+
+    bool runOnFunction(Function &Fn) {
+      MachineFunction &MF = MachineFunction::construct(&Fn, TM);
+      SelectionDAG DAG(MF, TM, *this);
+
+      std::cerr << "\n\n\n=== "
+                << DAG.getMachineFunction().getFunction()->getName() << "\n";
+
+      DAG.dump();
+      X86ISel(DAG).generateCode();
+      std::cerr << "\n\n\n";
+      return true;
+    }
+
+  public:  // Implementation of the SelectionDAGTargetBuilder class...
+    /// expandArguments - Add nodes to the DAG to indicate how to load arguments
+    /// off of the X86 stack.
+    void expandArguments(SelectionDAG &SD, MachineFunction &MF);
+  };
+}
+
+
+void ISel::expandArguments(SelectionDAG &SD, MachineFunction &F) {
+  // Add DAG nodes to load the arguments...  On entry to a function on the X86,
+  // the stack frame looks like this:
+  //
+  // [ESP] -- return address
+  // [ESP + 4] -- first argument (leftmost lexically)
+  // [ESP + 8] -- second argument, if first argument is four bytes in size
+  //    ... 
+  //
+  unsigned ArgOffset = 0;   // Frame mechanisms handle retaddr slot
+  MachineFrameInfo *MFI = F.getFrameInfo();
+  const Function &Fn = *F.getFunction();
+  
+  for (Function::const_aiterator I = Fn.abegin(), E = Fn.aend(); I != E; ++I) {
+    MVT::ValueType ObjectVT = SD.getValueType(I->getType());
+    unsigned ArgIncrement = 4;
+    unsigned ObjSize;
+    switch (ObjectVT) {
+    default: assert(0 && "Unhandled argument type!");
+    case MVT::i8:  ObjSize = 1;                break;
+    case MVT::i16: ObjSize = 2;                break;
+    case MVT::i32: ObjSize = 4;                break;
+    case MVT::i64: ObjSize = ArgIncrement = 8; break;
+    case MVT::f32: ObjSize = 4;                break;
+    case MVT::f64: ObjSize = ArgIncrement = 8; break;
+    }
+    // Create the frame index object for this incoming parameter...
+    int FI = MFI->CreateFixedObject(ObjSize, ArgOffset);
+    
+    // Create the SelectionDAG nodes corresponding to a load from this parameter
+    // FIXME:
+    SelectionDAGNode *FIN = new SelectionDAGNode(ISD::FrameIndex, MVT::i32);
+    FIN->addValue(new ReducedValue_FrameIndex_i32(FI));
+
+    SelectionDAGNode *Arg
+      = new SelectionDAGNode(ISD::Load, ObjectVT, F.begin(), FIN);
+
+    // Add the SelectionDAGNodes to the SelectionDAG... note that there is no
+    // reason to add chain nodes here.  We know that no loads ore stores will
+    // ever alias these loads, so we are free to perform the load at any time in
+    // the function
+    SD.addNode(FIN);
+    SD.addNodeForValue(Arg, I);
+
+    ArgOffset += ArgIncrement;   // Move on to the next argument...
+  }
+
+  // If the function takes variable number of arguments, make a frame index for
+  // the start of the first vararg value... for expansion of llvm.va_start.
+  if (Fn.getFunctionType()->isVarArg())
+    VarArgsFrameIndex = MFI->CreateFixedObject(1, ArgOffset);
+}
+
+
+/// createX86PatternInstructionSelector - This pass converts an LLVM function
+/// into a machine code representation using pattern matching and a machine
+/// description file.
+///
+Pass *createX86PatternInstructionSelector(TargetMachine &TM) {
+  return new ISel(TM);  
+}