[CodeGen] Support custom format of stack maps

Summary:
Add a hook to the GCMetadataPrinter for emitting stack maps in
custom format. The hook will be called at stack map generation
time. The default stack map format is used if there is no hook.

For this to be useful a few data structures and accessors are
exposed from the StackMaps class, so the custom printer can
access the stack map data.

This patch authored by Cherry Zhang <cherryyz@google.com>.

Reviewers: thanm, apilipenko, reames

Reviewed By: reames

Subscribers: reames, apilipenko, nemanjai, javed.absar, kbarton, jsji, llvm-commits

Differential Revision: https://reviews.llvm.org/D53892

llvm-svn: 347584

include/llvm/CodeGen/AsmPrinter.h

@@ -71,6 +71,7 @@ class MCTargetOptions;
 class MDNode;
 class Module;
 class raw_ostream;
+class StackMaps;
 class TargetLoweringObjectFile;
 class TargetMachine;
 
@@ -365,6 +366,9 @@ public:
   /// emit the proxies we previously omitted in EmitGlobalVariable.
   void emitGlobalGOTEquivs();
 
+  /// Emit the stack maps.
+  void emitStackMaps(StackMaps &SM);
+
   //===------------------------------------------------------------------===//
   // Overridable Hooks
   //===------------------------------------------------------------------===//

include/llvm/CodeGen/GCMetadataPrinter.h

@@ -29,6 +29,7 @@ class GCMetadataPrinter;
 class GCModuleInfo;
 class GCStrategy;
 class Module;
+class StackMaps;
 
 /// GCMetadataPrinterRegistry - The GC assembly printer registry uses all the
 /// defaults from Registry.
@@ -60,6 +61,11 @@ public:
   /// Called after the assembly for the module is generated by
   /// the AsmPrinter (but before target specific hooks)
   virtual void finishAssembly(Module &M, GCModuleInfo &Info, AsmPrinter &AP) {}
+
+  /// Called when the stack maps are generated. Return true if
+  /// stack maps with a custom format are generated. Otherwise
+  /// returns false and the default format will be used.
+  virtual bool emitStackMaps(StackMaps &SM, AsmPrinter &AP) { return false; }
 };
 
 } // end namespace llvm

lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -54,6 +54,7 @@
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/CodeGen/MachineOperand.h"
 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
+#include "llvm/CodeGen/StackMaps.h"
 #include "llvm/CodeGen/TargetFrameLowering.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 #include "llvm/CodeGen/TargetLowering.h"
@@ -2977,11 +2978,6 @@ GCMetadataPrinter *AsmPrinter::GetOrCreateGCPrinter(GCStrategy &S) {
   if (!S.usesMetadata())
     return nullptr;
 
-  assert(!S.useStatepoints() && "statepoints do not currently support custom"
-         " stackmap formats, please see the documentation for a description of"
-         " the default format.  If you really need a custom serialized format,"
-         " please file a bug");
-
   gcp_map_type &GCMap = getGCMap(GCMetadataPrinters);
   gcp_map_type::iterator GCPI = GCMap.find(&S);
   if (GCPI != GCMap.end())
@@ -3002,6 +2998,27 @@ GCMetadataPrinter *AsmPrinter::GetOrCreateGCPrinter(GCStrategy &S) {
   report_fatal_error("no GCMetadataPrinter registered for GC: " + Twine(Name));
 }
 
+void AsmPrinter::emitStackMaps(StackMaps &SM) {
+  GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
+  assert(MI && "AsmPrinter didn't require GCModuleInfo?");
+  bool NeedsDefault = false;
+  if (MI->begin() == MI->end())
+    // No GC strategy, use the default format.
+    NeedsDefault = true;
+  else
+    for (auto &I : *MI) {
+      if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(*I))
+        if (MP->emitStackMaps(SM, *this))
+          continue;
+      // The strategy doesn't have printer or doesn't emit custom stack maps.
+      // Use the default format.
+      NeedsDefault = true;
+    }
+
+  if (NeedsDefault)
+    SM.serializeToStackMapSection();
+}
+
 /// Pin vtable to this file.
 AsmPrinterHandler::~AsmPrinterHandler() = default;
 

lib/Target/AArch64/AArch64AsmPrinter.cpp

@@ -217,7 +217,7 @@ void AArch64AsmPrinter::EmitEndOfAsmFile(Module &M) {
     // linker can safely perform dead code stripping.  Since LLVM never
     // generates code that does this, it is always safe to set.
     OutStreamer->EmitAssemblerFlag(MCAF_SubsectionsViaSymbols);
-    SM.serializeToStackMapSection();
+    emitStackMaps(SM);
   }
 }
 

lib/Target/PowerPC/PPCAsmPrinter.cpp

@@ -327,7 +327,7 @@ MCSymbol *PPCAsmPrinter::lookUpOrCreateTOCEntry(MCSymbol *Sym) {
 }
 
 void PPCAsmPrinter::EmitEndOfAsmFile(Module &M) {
-  SM.serializeToStackMapSection();
+  emitStackMaps(SM);
 }
 
 void PPCAsmPrinter::LowerSTACKMAP(StackMaps &SM, const MachineInstr &MI) {

lib/Target/SystemZ/SystemZAsmPrinter.cpp

@@ -647,7 +647,7 @@ bool SystemZAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 }
 
 void SystemZAsmPrinter::EmitEndOfAsmFile(Module &M) {
-  SM.serializeToStackMapSection();
+  emitStackMaps(SM);
 }
 
 // Force static initialization.

lib/Target/X86/X86AsmPrinter.cpp

@@ -674,7 +674,7 @@ void X86AsmPrinter::EmitEndOfAsmFile(Module &M) {
     emitNonLazyStubs(MMI, *OutStreamer);
 
     // Emit stack and fault map information.
-    SM.serializeToStackMapSection();
+    emitStackMaps(SM);
     FM.serializeToFaultMapSection();
 
     // This flag tells the linker that no global symbols contain code that fall
@@ -695,12 +695,12 @@ void X86AsmPrinter::EmitEndOfAsmFile(Module &M) {
   }
 
   if (TT.isOSBinFormatCOFF()) {
-    SM.serializeToStackMapSection();
+    emitStackMaps(SM);
     return;
   }
 
   if (TT.isOSBinFormatELF()) {
-    SM.serializeToStackMapSection();
+    emitStackMaps(SM);
     FM.serializeToFaultMapSection();
     return;
   }