lib/Target/AMDGPU/AMDGPUFrameLowering.cpp

   1 //===----------------------- AMDGPUFrameLowering.cpp ----------------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //==-----------------------------------------------------------------------===//
   9 //
  10 // Interface to describe a layout of a stack frame on a AMDGPU target machine.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "AMDGPUFrameLowering.h"
  15
  16 using namespace llvm;
  17 AMDGPUFrameLowering::AMDGPUFrameLowering(StackDirection D, unsigned StackAl,
  18     int LAO, unsigned TransAl)
  19   : TargetFrameLowering(D, StackAl, LAO, TransAl) { }
  20
  21 AMDGPUFrameLowering::~AMDGPUFrameLowering() = default;
  22
  23 unsigned AMDGPUFrameLowering::getStackWidth(const MachineFunction &MF) const {
  24   // XXX: Hardcoding to 1 for now.
  25   //
  26   // I think the StackWidth should stored as metadata associated with the
  27   // MachineFunction.  This metadata can either be added by a frontend, or
  28   // calculated by a R600 specific LLVM IR pass.
  29   //
  30   // The StackWidth determines how stack objects are laid out in memory.
  31   // For a vector stack variable, like: int4 stack[2], the data will be stored
  32   // in the following ways depending on the StackWidth.
  33   //
  34   // StackWidth = 1:
  35   //
  36   // T0.X = stack[0].x
  37   // T1.X = stack[0].y
  38   // T2.X = stack[0].z
  39   // T3.X = stack[0].w
  40   // T4.X = stack[1].x
  41   // T5.X = stack[1].y
  42   // T6.X = stack[1].z
  43   // T7.X = stack[1].w
  44   //
  45   // StackWidth = 2:
  46   //
  47   // T0.X = stack[0].x
  48   // T0.Y = stack[0].y
  49   // T1.X = stack[0].z
  50   // T1.Y = stack[0].w
  51   // T2.X = stack[1].x
  52   // T2.Y = stack[1].y
  53   // T3.X = stack[1].z
  54   // T3.Y = stack[1].w
  55   //
  56   // StackWidth = 4:
  57   // T0.X = stack[0].x
  58   // T0.Y = stack[0].y
  59   // T0.Z = stack[0].z
  60   // T0.W = stack[0].w
  61   // T1.X = stack[1].x
  62   // T1.Y = stack[1].y
  63   // T1.Z = stack[1].z
  64   // T1.W = stack[1].w
  65   return 1;
  66 }