[Stackmap] Added callsite counts to emitted function information.

Summary:
It was previously not possible for tools to use solely the stackmap
information emitted to reconstruct the return addresses of callsites in
the map, which is necessary to use the information to walk a stack. This
patch adds per-function callsite counts when emitting the stackmap
section in order to resolve the problem. Note that this slightly alters
the stackmap format, so external tools parsing these maps will need to
be updated.

**Problem Details:**
Records only store their offset from the beginning of the function they
belong to. While these records and the functions are output in program
order, it is not possible to determine where the end of one function's
records are without the callsite count when processing the records to
compute return addresses.

Patch by Kavon Farvardin!

Reviewers: atrick, ributzka, sanjoy

Subscribers: nemanjai

Differential Revision: https://reviews.llvm.org/D23487

llvm-svn: 281532

1 files changed, 21 insertions, 13 deletions

diff --git a/llvm/lib/CodeGen/StackMaps.cpp b/llvm/lib/CodeGen/StackMaps.cpp
index 9e6fc3e094b..9b7dd400fc9 100644
--- a/llvm/lib/CodeGen/StackMaps.cpp
+++ b/llvm/lib/CodeGen/StackMaps.cpp
@@ -30,8 +30,8 @@ using namespace llvm;
 #define DEBUG_TYPE "stackmaps"
 
 static cl::opt<int> StackMapVersion(
-    "stackmap-version", cl::init(1),
-    cl::desc("Specify the stackmap encoding version (default = 1)"));
+    "stackmap-version", cl::init(2),
+    cl::desc("Specify the stackmap encoding version (default = 2)"));
 
 const char *StackMaps::WSMP = "Stack Maps: ";
 
@@ -74,7 +74,7 @@ unsigned PatchPointOpers::getNextScratchIdx(unsigned StartIdx) const {
 }
 
 StackMaps::StackMaps(AsmPrinter &AP) : AP(AP) {
-  if (StackMapVersion != 1)
+  if (StackMapVersion != 2)
     llvm_unreachable("Unsupported stackmap version!");
 }
 
@@ -335,13 +335,18 @@ void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
   CSInfos.emplace_back(CSOffsetExpr, ID, std::move(Locations),
                        std::move(LiveOuts));
 
-  // Record the stack size of the current function.
+  // Record the stack size of the current function and update callsite count.
   const MachineFrameInfo &MFI = AP.MF->getFrameInfo();
   const TargetRegisterInfo *RegInfo = AP.MF->getSubtarget().getRegisterInfo();
   bool HasDynamicFrameSize =
       MFI.hasVarSizedObjects() || RegInfo->needsStackRealignment(*(AP.MF));
-  FnStackSize[AP.CurrentFnSym] =
-      HasDynamicFrameSize ? UINT64_MAX : MFI.getStackSize();
+  uint64_t FrameSize = HasDynamicFrameSize ? UINT64_MAX : MFI.getStackSize();
+
+  auto CurrentIt = FnInfos.find(AP.CurrentFnSym);
+  if (CurrentIt != FnInfos.end())
+    CurrentIt->second.RecordCount++;
+  else
+    FnInfos.insert(std::make_pair(AP.CurrentFnSym, FunctionInfo(FrameSize)));
 }
 
 void StackMaps::recordStackMap(const MachineInstr &MI) {
@@ -387,7 +392,7 @@ void StackMaps::recordStatepoint(const MachineInstr &MI) {
 /// Emit the stackmap header.
 ///
 /// Header {
-///   uint8  : Stack Map Version (currently 1)
+///   uint8  : Stack Map Version (currently 2)
 ///   uint8  : Reserved (expected to be 0)
 ///   uint16 : Reserved (expected to be 0)
 /// }
@@ -401,8 +406,8 @@ void StackMaps::emitStackmapHeader(MCStreamer &OS) {
   OS.EmitIntValue(0, 2);               // Reserved.
 
   // Num functions.
-  DEBUG(dbgs() << WSMP << "#functions = " << FnStackSize.size() << '\n');
-  OS.EmitIntValue(FnStackSize.size(), 4);
+  DEBUG(dbgs() << WSMP << "#functions = " << FnInfos.size() << '\n');
+  OS.EmitIntValue(FnInfos.size(), 4);
   // Num constants.
   DEBUG(dbgs() << WSMP << "#constants = " << ConstPool.size() << '\n');
   OS.EmitIntValue(ConstPool.size(), 4);
@@ -416,15 +421,18 @@ void StackMaps::emitStackmapHeader(MCStreamer &OS) {
 /// StkSizeRecord[NumFunctions] {
 ///   uint64 : Function Address
 ///   uint64 : Stack Size
+///   uint64 : Record Count
 /// }
 void StackMaps::emitFunctionFrameRecords(MCStreamer &OS) {
   // Function Frame records.
   DEBUG(dbgs() << WSMP << "functions:\n");
-  for (auto const &FR : FnStackSize) {
+  for (auto const &FR : FnInfos) {
     DEBUG(dbgs() << WSMP << "function addr: " << FR.first
-                 << " frame size: " << FR.second);
+                 << " frame size: " << FR.second.StackSize
+                 << " callsite count: " << FR.second.RecordCount << '\n');
     OS.EmitSymbolValue(FR.first, 8);
-    OS.EmitIntValue(FR.second, 8);
+    OS.EmitIntValue(FR.second.StackSize, 8);
+    OS.EmitIntValue(FR.second.RecordCount, 8);
   }
 }
 
@@ -525,7 +533,7 @@ void StackMaps::serializeToStackMapSection() {
   // Bail out if there's no stack map data.
   assert((!CSInfos.empty() || ConstPool.empty()) &&
          "Expected empty constant pool too!");
-  assert((!CSInfos.empty() || FnStackSize.empty()) &&
+  assert((!CSInfos.empty() || FnInfos.empty()) &&
          "Expected empty function record too!");
   if (CSInfos.empty())
     return;