[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

1 files changed, 22 insertions, 5 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 526f7ce3083..3ccf99ade89 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/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;