Add a local stack object block allocation pass. This is still an

experimental pass that allocates locals relative to one another before
register allocation and then assigns them to actual stack slots as a block
later in PEI. This will eventually allow targets with limited index offset
range to allocate additional base registers (not just FP and SP) to
more efficiently reference locals, as well as handle situations where
locals cannot be referenced via SP or FP at all (dynamic stack realignment
together with variable sized objects, for example). It's currently
incomplete and almost certainly buggy. Work in progress.

Disabled by default and gated via the -enable-local-stack-alloc command
line option.

rdar://8277890



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@111059 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 64 insertions, 2 deletions

diff --git a/include/llvm/CodeGen/MachineFrameInfo.h b/include/llvm/CodeGen/MachineFrameInfo.h
index 374d6e5..7c98b36 100644
--- a/include/llvm/CodeGen/MachineFrameInfo.h
+++ b/include/llvm/CodeGen/MachineFrameInfo.h
@@ -15,6 +15,7 @@
 #define LLVM_CODEGEN_MACHINEFRAMEINFO_H
 
 #include "llvm/ADT/SmallVector.h"
+//#include "llvm/ADT/IndexedMap.h"
 #include "llvm/System/DataTypes.h"
 #include <cassert>
 #include <vector>
@@ -103,10 +104,14 @@ class MachineFrameInfo {
     // protector.
     bool MayNeedSP;
 
+    // PreAllocated - If true, the object was mapped into the local frame
+    // block and doesn't need additional handling for allocation beyond that.
+    bool PreAllocated;
+
     StackObject(uint64_t Sz, unsigned Al, int64_t SP, bool IM,
                 bool isSS, bool NSP)
       : SPOffset(SP), Size(Sz), Alignment(Al), isImmutable(IM),
-        isSpillSlot(isSS), MayNeedSP(NSP) {}
+        isSpillSlot(isSS), MayNeedSP(NSP), PreAllocated(false) {}
   };
 
   /// Objects - The list of stack objects allocated...
@@ -195,8 +200,20 @@ class MachineFrameInfo {
   ///
   const TargetFrameInfo &TFI;
 
+  /// LocalFrameObjects - References to frame indices which are mapped
+  /// into the local frame allocation block. <FrameIdx, LocalOffset>
+  SmallVector<std::pair<int, int64_t>, 32> LocalFrameObjects;
+
+  /// LocalFrameSize - Size of the pre-allocated local frame block.
+  int64_t LocalFrameSize;
+
+  /// LocalFrameBaseOffset - The base offset from the stack pointer at
+  /// function entry of the local frame blob. Set by PEI for use by
+  /// target in eliminateFrameIndex().
+  int64_t LocalFrameBaseOffset;
+
 public:
-  explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
+    explicit MachineFrameInfo(const TargetFrameInfo &tfi) : TFI(tfi) {
     StackSize = NumFixedObjects = OffsetAdjustment = MaxAlignment = 0;
     HasVarSizedObjects = false;
     FrameAddressTaken = false;
@@ -206,6 +223,8 @@ public:
     StackProtectorIdx = -1;
     MaxCallFrameSize = 0;
     CSIValid = false;
+    LocalFrameSize = 0;
+    LocalFrameBaseOffset = 0;
   }
 
   /// hasStackObjects - Return true if there are any stack objects in this
@@ -252,6 +271,42 @@ public:
   ///
   unsigned getNumObjects() const { return Objects.size(); }
 
+  /// mapLocalFrameObject - Map a frame index into the local object block
+  void mapLocalFrameObject(int ObjectIndex, int64_t Offset) {
+    LocalFrameObjects.push_back(std::pair<int, int64_t>(ObjectIndex, Offset));
+    Objects[ObjectIndex + NumFixedObjects].PreAllocated = true;
+  }
+
+  /// getLocalFrameObjectMap - Get the local offset mapping for a for an object
+  std::pair<int, int64_t> getLocalFrameObjectMap(int i) {
+    assert (i >= 0 && (unsigned)i < LocalFrameObjects.size() &&
+            "Invalid local object reference!");
+    return LocalFrameObjects[i];
+  }
+
+  /// getLocalFrameObjectCount - Return the number of objects allocated into
+  /// the local object block.
+  int64_t getLocalFrameObjectCount() { return LocalFrameObjects.size(); }
+
+  /// setLocalFrameBaseOffset - Set the base SP offset of the local frame
+  /// blob.
+  void setLocalFrameBaseOffset(int64_t o) { LocalFrameBaseOffset = o; }
+
+  /// getLocalFrameBaseOffset - Get the base SP offset of the local frame
+  /// blob.
+  int64_t getLocalFrameBaseOffset() const { return LocalFrameBaseOffset; }
+
+  /// getLocalFrameSize - Get the size of the local object blob.
+  int64_t getLocalFrameSize() const { return LocalFrameSize; }
+
+  /// isObjectPreAllocated - Return true if the object was pre-allocated into
+  /// the local block.
+  bool isObjectPreAllocated(int ObjectIdx) const {
+    assert(unsigned(ObjectIdx+NumFixedObjects) < Objects.size() &&
+           "Invalid Object Idx!");
+    return Objects[ObjectIdx+NumFixedObjects].PreAllocated;
+  }
+
   /// getObjectSize - Return the size of the specified object.
   ///
   int64_t getObjectSize(int ObjectIdx) const {
diff --git a/include/llvm/CodeGen/Passes.h b/include/llvm/CodeGen/Passes.h
index 3e6b3e1..0fa498a 100644
--- a/include/llvm/CodeGen/Passes.h
+++ b/include/llvm/CodeGen/Passes.h
@@ -198,6 +198,13 @@ namespace llvm {
   /// the GCC-style builtin setjmp/longjmp (sjlj) to handling EH control flow.
   FunctionPass *createSjLjEHPass(const TargetLowering *tli);
 
+  /// createLocalStackSlotAllocationPass - This pass assigns local frame
+  /// indices to stack slots relative to one another and allocates
+  /// base registers to access them when it is estimated by the target to
+  /// be out of range of normal frame pointer or stack pointer index
+  /// addressing.
+  FunctionPass *createLocalStackSlotAllocationPass();
+
 } // End llvm namespace
 
 #endif