Initial checkin of X86 Register File description

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7509 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/X86/X86RegisterInfo.td b/lib/Target/X86/X86RegisterInfo.td
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+//===- X86RegisterInfo.td - Describe the X86 Register File ------*- C++ -*-===//
+//
+// This file describes the X86 Register file, defining the registers themselves,
+// aliases between the registers, and the register classes built out of the
+// registers.
+//
+//===----------------------------------------------------------------------===//
+
+//===----------------------------------------------------------------------===//
+//  Register definitions...
+//
+set Namespace = "X86" in {
+  // 32-bit registers
+  def EAX : Register; def ECX : Register;
+  def EDX : Register; def EBX : Register;
+  def ESP : Register; def EBP : Register;
+  def ESI : Register; def EDI : Register;
+  
+  // 16-bit registers
+  def AX : Register; def CX : Register;
+  def DX : Register; def BX : Register;
+  def SP : Register; def BP : Register;
+  def SI : Register; def DI : Register;
+  
+  // 8-bit registers
+  def AL : Register; def CL : Register;
+  def DL : Register; def BL : Register;
+  def AH : Register; def CH : Register;
+  def DH : Register; def BH : Register;
+  
+  // Pseudo Floating Point registers
+  def FP0 : Register; def FP1 : Register;
+  def FP2 : Register; def FP3 : Register;
+  def FP4 : Register; def FP5 : Register;
+  def FP6 : Register; 
+
+  // Floating point stack registers
+  def ST0 : Register; def ST1 : Register;
+  def ST2 : Register; def ST3 : Register;
+  def ST4 : Register; def ST5 : Register;
+  def ST6 : Register; def ST7 : Register; 
+  
+  // Flags, Segment registers, etc...
+  
+  // This is a slimy hack to make it possible to say that flags are clobbered...
+  // Ideally we'd model instructions based on which particular flag(s) they
+  // could clobber. 
+  def EFLAGS : Register;
+}
+
+//===----------------------------------------------------------------------===//
+// Register alias definitions... define which registers alias which others.  We
+// only specify which registers the small registers alias, because the register
+// file generator is smart enough to figure out that AL aliases AX if we tell it
+// that AX aliases AL (for example).
+//
+def : RegisterAliases<AL, [AX, EAX]>; def : RegisterAliases<BL, [BX, EBX]>;
+def : RegisterAliases<CL, [CX, ECX]>; def : RegisterAliases<DL, [DX, EDX]>;
+def : RegisterAliases<AH, [AX, EAX]>; def : RegisterAliases<BH, [BX, EBX]>;
+def : RegisterAliases<CH, [CX, ECX]>; def : RegisterAliases<DH, [DX, EDX]>;
+
+def : RegisterAliases<AX, [EAX]>;     def : RegisterAliases<BX, [EBX]>;
+def : RegisterAliases<CX, [ECX]>;     def : RegisterAliases<DX, [EDX]>;
+def : RegisterAliases<SI, [ESI]>;     def : RegisterAliases<DI, [EDI]>;
+def : RegisterAliases<SP, [ESP]>;     def : RegisterAliases<BP, [EBP]>;
+
+//===----------------------------------------------------------------------===//
+// Register Class Definitions... now that we have all of the pieces, define the
+// top-level register classes.  The order specified in the register list is
+// implicitly defined to be the register allocation order.
+//
+def r8  : RegisterClass<i8,  1, [AL, CL, DL, BL, AH, CH, DH, BH]>;
+def r16 : RegisterClass<i16, 2, [AX, CX, DX, BX, SI, DI, BP, SP]> {
+  set Methods = [{
+    iterator allocation_order_end(MachineFunction &MF) const {
+      if (hasFP(MF))     // Does the function dedicate EBP to being a frame ptr?
+       return end()-2;  // If so, don't allocate SP or BP
+      else
+       return end()-1;  // If not, just don't allocate SP
+    }
+  }];
+}
+
+def r32 : RegisterClass<i32, 4, [EAX, ECX, EDX, EBX, ESI, EDI, EBP, ESP]> {
+  set Methods = [{
+    iterator allocation_order_end(MachineFunction &MF) const {
+      if (hasFP(MF))     // Does the function dedicate EBP to being a frame ptr?
+        return end()-2;  // If so, don't allocate ESP or EBP
+      else
+        return end()-1;  // If not, just don't allocate ESP
+    }
+  }];
+}
+
+def rFP : RegisterClass<f80, 4, [FP0, FP1, FP2, FP3, FP4, FP5, FP6]>;
+
+// Registers which cannot be allocated... and are thus left unnamed.
+def : RegisterClass<f80, 4, [ST0, ST1, ST2, ST3, ST4, ST5, ST6, ST7]>;
+def : RegisterClass<i16, 2, [EFLAGS]>;
+
+
+
+//===----------------------------------------------------------------------===//
+// Finally, define the global RegisterInfo implementation.
+//
+
+def : RegisterInfo {
+  // Specify the class name for the register info generator to make.
+  set ClassName = "X86GenRegisterInfo";
+  
+  // Specify the calle saved registers.
+  set CalleeSavedRegisters = [ESI, EDI, EBX, EBP];
+
+  // Yes, pointers are 32-bits in size.
+  set PointerType = i32;
+}