[lld/coff] Add parsing for /pdbpagesize: flag

It's not used for anything yet, but we now accept `/pdbpagesize:4096`
(the default behavior) and we give arguably more useful diagnostics
for other values.

It's plumbed through to the MSF layer, so just uncommenting out
the bit in DriverUtils.cpp that rejects args other than 4096 is enough
to try other values.

Differential Revision: https://reviews.llvm.org/D112871

lld/COFF/Config.h

@@ -124,6 +124,7 @@ struct Configuration {
   std::vector<std::string> natvisFiles;
   llvm::StringMap<std::string> namedStreams;
   llvm::SmallString<128> pdbAltPath;
+  int pdbPageSize = 4096;
   llvm::SmallString<128> pdbPath;
   llvm::SmallString<128> pdbSourcePath;
   std::vector<llvm::StringRef> argv;

lld/COFF/Driver.cpp

@@ -1428,6 +1428,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
       config->pdbPath = arg->getValue();
     if (auto *arg = args.getLastArg(OPT_pdbaltpath))
       config->pdbAltPath = arg->getValue();
+    if (auto *arg = args.getLastArg(OPT_pdbpagesize))
+      parsePDBPageSize(arg->getValue());
     if (args.hasArg(OPT_natvis))
       config->natvisFiles = args.getAllArgValues(OPT_natvis);
     if (args.hasArg(OPT_pdbstream)) {

lld/COFF/Driver.h

@@ -176,6 +176,7 @@ void parseSubsystem(StringRef arg, WindowsSubsystem *sys, uint32_t *major,
 
 void parseAlternateName(StringRef);
 void parseMerge(StringRef);
+void parsePDBPageSize(StringRef);
 void parseSection(StringRef);
 void parseAligncomm(StringRef);
 

lld/COFF/DriverUtils.cpp

@@ -175,6 +175,26 @@ void parseMerge(StringRef s) {
   }
 }
 
+void parsePDBPageSize(StringRef s) {
+  int v;
+  if (s.getAsInteger(0, v)) {
+    error("/pdbpagesize: invalid argument: " + s);
+    return;
+  }
+  if (v != 4096 && v != 8192 && v != 16384 && v != 32768) {
+    error("/pdbpagesize: invalid argument: " + s);
+    return;
+  }
+
+  // FIXME: Remove this once other page sizes work.
+  if (v != 4096) {
+    warn("/pdbpagesize: page sizes != 4096 not yet implemented, ignoring flag");
+    v = 4096;
+  }
+
+  config->pdbPageSize = v;
+}
+
 static uint32_t parseSectionAttributes(StringRef s) {
   uint32_t ret = 0;
   for (char c : s.lower()) {

lld/COFF/Options.td

@@ -78,8 +78,9 @@ def order   : P<"order", "Put functions in order">;
 def out     : P<"out", "Path to file to write output">;
 def natvis : P<"natvis", "Path to natvis file to embed in the PDB">;
 def pdb : P<"pdb", "PDB file path">;
-def pdbstripped : P<"pdbstripped", "Stripped PDB file path">;
 def pdbaltpath : P<"pdbaltpath", "PDB file path to embed in the image">;
+def pdbpagesize : P<"pdbpagesize", "PDB page size">;
+def pdbstripped : P<"pdbstripped", "Stripped PDB file path">;
 def pdbstream : Joined<["/", "-", "/?", "-?"], "pdbstream:">,
     MetaVarName<"<name>=<file>">,
     HelpText<"Embed the contents of <file> in the PDB as named stream <name>">;

lld/COFF/PDB.cpp

@@ -1588,7 +1588,7 @@ void lld::coff::createPDB(COFFLinkerContext &ctx,
 }
 
 void PDBLinker::initialize(llvm::codeview::DebugInfo *buildId) {
-  exitOnErr(builder.initialize(4096)); // 4096 is blocksize
+  exitOnErr(builder.initialize(config->pdbPageSize));
 
   buildId->Signature.CVSignature = OMF::Signature::PDB70;
   // Signature is set to a hash of the PDB contents when the PDB is done.

lld/test/COFF/pdbpagesize.test

@@ -0,0 +1,15 @@
+# RUN: yaml2obj %p/Inputs/empty.yaml -o %t.obj
+
+# RUN: not lld-link /entry:main %t.obj /out:%t.exe /debug /pdbpagesize:hi 2>&1 \
+# RUN:     | FileCheck --check-prefix=INVALID %s
+# RUN: not lld-link /entry:main %t.obj /out:%t.exe /debug /pdbpagesize:15 2>&1 \
+# RUN:     | FileCheck --check-prefix=INVALID %s
+# INVALID: error: /pdbpagesize: invalid argument:
+
+# RUN: lld-link /entry:main %t.obj /out:%t.exe /debug /pdbpagesize:4096
+# RUN: llvm-pdbutil pdb2yaml %t.pdb | FileCheck --check-prefix=PAGE4096 %s
+# PAGE4096: BlockSize: 4096
+
+# RUN: lld-link /entry:main %t.obj /out:%t.exe /debug /pdbpagesize:8192 2>&1 \
+# RUN:     | FileCheck --check-prefix=TODO %s
+# TODO: warning: /pdbpagesize: page sizes != 4096 not yet implemented, ignoring flag

llvm/include/llvm/DebugInfo/MSF/MSFCommon.h

@@ -93,6 +93,9 @@ inline bool isValidBlockSize(uint32_t Size) {
   case 1024:
   case 2048:
   case 4096:
+  case 8192:
+  case 16384:
+  case 32768:
     return true;
   }
   return false;