1 files changed, 169 insertions, 0 deletions
diff --git a/lib/CodeGen/LocalStackSlotAllocation.cpp b/lib/CodeGen/LocalStackSlotAllocation.cpp
new file mode 100644
index 0000000000..dabfb469c3
--- /dev/null
+++ b/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -0,0 +1,169 @@
+//===- LocalStackSlotAllocation.cpp - Pre-allocate locals to stack slots --===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass assigns local frame indices to stack slots relative to one another
+// and allocates additional base registers to access them when the target
+// estimates the are likely to be out of range of stack pointer and frame
+// pointer relative addressing.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "localstackalloc"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Instructions.h"
+#include "llvm/Intrinsics.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/LLVMContext.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Target/TargetFrameInfo.h"
+
+using namespace llvm;
+
+STATISTIC(NumAllocations, "Number of frame indices processed");
+
+namespace {
+  class LocalStackSlotPass: public MachineFunctionPass {
+    int64_t LocalStackSize;
+
+    void calculateFrameObjectOffsets(MachineFunction &Fn);
+  public:
+    static char ID; // Pass identification, replacement for typeid
+    explicit LocalStackSlotPass() : MachineFunctionPass(ID) { }
+    bool runOnMachineFunction(MachineFunction &MF);
+
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.setPreservesCFG();
+      MachineFunctionPass::getAnalysisUsage(AU);
+    }
+    const char *getPassName() const {
+      return "Local Stack Slot Allocation";
+    }
+
+  private:
+  };
+} // end anonymous namespace
+
+char LocalStackSlotPass::ID = 0;
+
+FunctionPass *llvm::createLocalStackSlotAllocationPass() {
+  return new LocalStackSlotPass();
+}
+
+bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
+  calculateFrameObjectOffsets(MF);
+  DEBUG(dbgs() << LocalStackSize << " bytes of local storage pre-allocated\n");
+  return true;
+}
+
+/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
+static inline void
+AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
+                  unsigned &MaxAlign) {
+  unsigned Align = MFI->getObjectAlignment(FrameIdx);
+
+  // If the alignment of this object is greater than that of the stack, then
+  // increase the stack alignment to match.
+  MaxAlign = std::max(MaxAlign, Align);
+
+  // Adjust to alignment boundary.
+  Offset = (Offset + Align - 1) / Align * Align;
+
+  DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
+        << Offset << "\n");
+  MFI->mapLocalFrameObject(FrameIdx, Offset);
+  Offset += MFI->getObjectSize(FrameIdx);
+
+  ++NumAllocations;
+}
+
+/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
+/// abstract stack objects.
+///
+void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
+  const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
+
+  // Loop over all of the stack objects, assigning sequential addresses...
+  MachineFrameInfo *MFI = Fn.getFrameInfo();
+  int64_t Offset = 0;
+  unsigned MaxAlign = MFI->getMaxAlignment();
+
+  // Make sure that the stack protector comes before the local variables on the
+  // stack.
+  SmallSet<int, 16> LargeStackObjs;
+  if (MFI->getStackProtectorIndex() >= 0) {
+    AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset, MaxAlign);
+
+    // Assign large stack objects first.
+    for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+      if (MFI->isDeadObjectIndex(i))
+        continue;
+      if (MFI->getStackProtectorIndex() == (int)i)
+        continue;
+      if (!MFI->MayNeedStackProtector(i))
+        continue;
+
+      AdjustStackOffset(MFI, i, Offset, MaxAlign);
+      LargeStackObjs.insert(i);
+    }
+  }
+
+  // Then assign frame offsets to stack objects that are not used to spill
+  // callee saved registers.
+  for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
+    if (MFI->isDeadObjectIndex(i))
+      continue;
+    if (MFI->getStackProtectorIndex() == (int)i)
+      continue;
+    if (LargeStackObjs.count(i))
+      continue;
+
+    AdjustStackOffset(MFI, i, Offset, MaxAlign);
+  }
+
+  const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
+  if (!RegInfo->targetHandlesStackFrameRounding()) {
+    // If we have reserved argument space for call sites in the function
+    // immediately on entry to the current function, count it as part of the
+    // overall stack size.
+    if (MFI->adjustsStack() && RegInfo->hasReservedCallFrame(Fn))
+      Offset += MFI->getMaxCallFrameSize();
+
+    // Round up the size to a multiple of the alignment.  If the function has
+    // any calls or alloca's, align to the target's StackAlignment value to
+    // ensure that the callee's frame or the alloca data is suitably aligned;
+    // otherwise, for leaf functions, align to the TransientStackAlignment
+    // value.
+    unsigned StackAlign;
+    if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
+        (RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
+      StackAlign = TFI.getStackAlignment();
+    else
+      StackAlign = TFI.getTransientStackAlignment();
+
+    // If the frame pointer is eliminated, all frame offsets will be relative to
+    // SP not FP. Align to MaxAlign so this works.
+    StackAlign = std::max(StackAlign, MaxAlign);
+    unsigned AlignMask = StackAlign - 1;
+    Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
+  }
+
+  // Remember how big this blob of stack space is
+  LocalStackSize = Offset;
+}