[Assembler] Enable nicer diagnostics for inline assembly.

Summary:
Enables source location in diagnostic messages from the backend.  This
is after parsing, during finalization.  This requires the SourceMgr, the
inline assembly string buffer, and DiagInfo to still be alive after
EmitInlineAsm returns.

This patch creates a single SourceMgr for inline assembly inside the
AsmPrinter.  MCContext gets a pointer to this SourceMgr.  Using one
SourceMgr per call to EmitInlineAsm would make it difficult for
MCContext to figure out in which SourceMgr the SMLoc is located, while a
single SourceMgr can figure it out if it has multiple buffers.

The Str argument to EmitInlineAsm is copied into a buffer and owned by
the inline asm SourceMgr.  This ensures that DiagHandlers won't print
garbage.  (Clang emits a "note: instantiated into assembly here", which
refers to this string.)

The AsmParser gets destroyed before finalization, which means that the
DiagHandlers the AsmParser installs into the SourceMgr will be stale.
Restore the saved DiagHandlers.

Since now we're using just one SourceMgr for multiple inline asm
strings, we need to tell the AsmParser which buffer it needs to parse
currently.  Hand a buffer id -- returned from SourceMgr::
AddNewSourceBuffer -- to the AsmParser.

Reviewers: rnk, grosbach, compnerd, rengolin, rovka, anemet

Reviewed By: rnk

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D29441

llvm-svn: 294433

1 files changed, 29 insertions, 31 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
index 57864e4e4d4..165b8eea094 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
@@ -40,19 +40,12 @@ using namespace llvm;
 
 #define DEBUG_TYPE "asm-printer"
 
-namespace {
-  struct SrcMgrDiagInfo {
-    const MDNode *LocInfo;
-    LLVMContext::InlineAsmDiagHandlerTy DiagHandler;
-    void *DiagContext;
-  };
-}
-
 /// srcMgrDiagHandler - This callback is invoked when the SourceMgr for an
 /// inline asm has an error in it.  diagInfo is a pointer to the SrcMgrDiagInfo
 /// struct above.
 static void srcMgrDiagHandler(const SMDiagnostic &Diag, void *diagInfo) {
-  SrcMgrDiagInfo *DiagInfo = static_cast<SrcMgrDiagInfo *>(diagInfo);
+  AsmPrinter::SrcMgrDiagInfo *DiagInfo =
+      static_cast<AsmPrinter::SrcMgrDiagInfo *>(diagInfo);
   assert(DiagInfo && "Diagnostic context not passed down?");
 
   // If the inline asm had metadata associated with it, pull out a location
@@ -99,35 +92,34 @@ void AsmPrinter::EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
     return;
   }
 
-  SourceMgr SrcMgr;
-  SrcMgr.setIncludeDirs(MCOptions.IASSearchPaths);
+  if (!DiagInfo) {
+    DiagInfo = make_unique<SrcMgrDiagInfo>();
 
-  SrcMgrDiagInfo DiagInfo;
-
-  // If the current LLVMContext has an inline asm handler, set it in SourceMgr.
-  LLVMContext &LLVMCtx = MMI->getModule()->getContext();
-  bool HasDiagHandler = false;
-  if (LLVMCtx.getInlineAsmDiagnosticHandler() != nullptr) {
-    // If the source manager has an issue, we arrange for srcMgrDiagHandler
-    // to be invoked, getting DiagInfo passed into it.
-    DiagInfo.LocInfo = LocMDNode;
-    DiagInfo.DiagHandler = LLVMCtx.getInlineAsmDiagnosticHandler();
-    DiagInfo.DiagContext = LLVMCtx.getInlineAsmDiagnosticContext();
-    SrcMgr.setDiagHandler(srcMgrDiagHandler, &DiagInfo);
-    HasDiagHandler = true;
+    MCContext &Context = MMI->getContext();
+    Context.setInlineSourceManager(&DiagInfo->SrcMgr);
+
+    LLVMContext &LLVMCtx = MMI->getModule()->getContext();
+    if (LLVMCtx.getInlineAsmDiagnosticHandler()) {
+      DiagInfo->DiagHandler = LLVMCtx.getInlineAsmDiagnosticHandler();
+      DiagInfo->DiagContext = LLVMCtx.getInlineAsmDiagnosticContext();
+      DiagInfo->SrcMgr.setDiagHandler(srcMgrDiagHandler, DiagInfo.get());
+    }
   }
 
+  SourceMgr &SrcMgr = DiagInfo->SrcMgr;
+  SrcMgr.setIncludeDirs(MCOptions.IASSearchPaths);
+  DiagInfo->LocInfo = LocMDNode;
+
   std::unique_ptr<MemoryBuffer> Buffer;
-  if (isNullTerminated)
-    Buffer = MemoryBuffer::getMemBuffer(Str, "<inline asm>");
-  else
-    Buffer = MemoryBuffer::getMemBufferCopy(Str, "<inline asm>");
+  // The inline asm source manager will outlive Str, so make a copy of the
+  // string for SourceMgr to own.
+  Buffer = MemoryBuffer::getMemBufferCopy(Str, "<inline asm>");
 
   // Tell SrcMgr about this buffer, it takes ownership of the buffer.
-  SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
+  unsigned BufNum = SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());
 
   std::unique_ptr<MCAsmParser> Parser(
-      createMCAsmParser(SrcMgr, OutContext, *OutStreamer, *MAI));
+      createMCAsmParser(SrcMgr, OutContext, *OutStreamer, *MAI, BufNum));
 
   // We create a new MCInstrInfo here since we might be at the module level
   // and not have a MachineFunction to initialize the TargetInstrInfo from and
@@ -151,7 +143,13 @@ void AsmPrinter::EmitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
   int Res = Parser->Run(/*NoInitialTextSection*/ true,
                         /*NoFinalize*/ true);
   emitInlineAsmEnd(STI, &TAP->getSTI());
-  if (Res && !HasDiagHandler)
+
+  // LocInfo cannot be used for error generation from the backend.
+  // FIXME: associate LocInfo with the SourceBuffer to improve backend
+  // messages.
+  DiagInfo->LocInfo = nullptr;
+
+  if (Res && !DiagInfo->DiagHandler)
     report_fatal_error("Error parsing inline asm\n");
 }