Revert "[MC] Remove UseAssemblerInfoForParsing"

This reverts commit 03c53c6.

This causes very large compile-time regressions in some cases,
e.g. sqlite3 at O0 regresses by 5%.

Author: nikic

clang/tools/driver/cc1as_main.cpp

@@ -576,6 +576,9 @@ static bool ExecuteAssemblerImpl(AssemblerInvocation &Opts,
     Str.get()->emitZeros(1);
   }
 
+  // Assembly to object compilation should leverage assembly info.
+  Str->setUseAssemblerInfoForParsing(true);
+
   bool Failed = false;
 
   std::unique_ptr<MCAsmParser> Parser(

llvm/include/llvm/MC/MCStreamer.h

@@ -245,6 +245,8 @@ class MCStreamer {
   /// requires.
   unsigned NextWinCFIID = 0;
 
+  bool UseAssemblerInfoForParsing;
+
   /// Is the assembler allowed to insert padding automatically?  For
   /// correctness reasons, we sometimes need to ensure instructions aren't
   /// separated in unexpected ways.  At the moment, this feature is only
@@ -294,10 +296,11 @@ class MCStreamer {
 
   MCContext &getContext() const { return Context; }
 
-  // MCObjectStreamer has an MCAssembler and allows more expression folding at
-  // parse time.
   virtual MCAssembler *getAssemblerPtr() { return nullptr; }
 
+  void setUseAssemblerInfoForParsing(bool v) { UseAssemblerInfoForParsing = v; }
+  bool getUseAssemblerInfoForParsing() { return UseAssemblerInfoForParsing; }
+
   MCTargetStreamer *getTargetStreamer() {
     return TargetStreamer.get();
   }

llvm/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp

@@ -102,6 +102,9 @@ void AsmPrinter::emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
   std::unique_ptr<MCAsmParser> Parser(
       createMCAsmParser(SrcMgr, OutContext, *OutStreamer, *MAI, BufNum));
 
+  // Do not use assembler-level information for parsing inline assembly.
+  OutStreamer->setUseAssemblerInfoForParsing(false);
+
   // 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
   // we only need MCInstrInfo for asm parsing. We create one unconditionally

llvm/lib/MC/MCObjectStreamer.cpp

@@ -40,7 +40,14 @@ MCObjectStreamer::MCObjectStreamer(MCContext &Context,
 
 MCObjectStreamer::~MCObjectStreamer() = default;
 
-MCAssembler *MCObjectStreamer::getAssemblerPtr() { return Assembler.get(); }
+// AssemblerPtr is used for evaluation of expressions and causes
+// difference between asm and object outputs. Return nullptr to in
+// inline asm mode to limit divergence to assembly inputs.
+MCAssembler *MCObjectStreamer::getAssemblerPtr() {
+  if (getUseAssemblerInfoForParsing())
+    return Assembler.get();
+  return nullptr;
+}
 
 void MCObjectStreamer::addPendingLabel(MCSymbol* S) {
   MCSection *CurSection = getCurrentSectionOnly();

llvm/lib/MC/MCStreamer.cpp

@@ -93,7 +93,7 @@ void MCTargetStreamer::emitAssignment(MCSymbol *Symbol, const MCExpr *Value) {}
 
 MCStreamer::MCStreamer(MCContext &Ctx)
     : Context(Ctx), CurrentWinFrameInfo(nullptr),
-      CurrentProcWinFrameInfoStartIndex(0) {
+      CurrentProcWinFrameInfoStartIndex(0), UseAssemblerInfoForParsing(false) {
   SectionStack.push_back(std::pair<MCSectionSubPair, MCSectionSubPair>());
 }
 

llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

@@ -517,9 +517,12 @@ bool AMDGPUAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
 
   DumpCodeInstEmitter = nullptr;
   if (STM.dumpCode()) {
-    // For -dumpcode, get the assembler out of the streamer. This only works
-    // with -filetype=obj.
+    // For -dumpcode, get the assembler out of the streamer, even if it does
+    // not really want to let us have it. This only works with -filetype=obj.
+    bool SaveFlag = OutStreamer->getUseAssemblerInfoForParsing();
+    OutStreamer->setUseAssemblerInfoForParsing(true);
     MCAssembler *Assembler = OutStreamer->getAssemblerPtr();
+    OutStreamer->setUseAssemblerInfoForParsing(SaveFlag);
     if (Assembler)
       DumpCodeInstEmitter = Assembler->getEmitterPtr();
   }

llvm/lib/Target/SPIRV/SPIRVAsmPrinter.cpp

@@ -114,9 +114,12 @@ void SPIRVAsmPrinter::emitEndOfAsmFile(Module &M) {
   // Bound is an approximation that accounts for the maximum used register
   // number and number of generated OpLabels
   unsigned Bound = 2 * (ST->getBound() + 1) + NLabels;
+  bool FlagToRestore = OutStreamer->getUseAssemblerInfoForParsing();
+  OutStreamer->setUseAssemblerInfoForParsing(true);
   if (MCAssembler *Asm = OutStreamer->getAssemblerPtr())
     Asm->setBuildVersion(static_cast<MachO::PlatformType>(0), Major, Minor,
                          Bound, VersionTuple(Major, Minor, 0, Bound));
+  OutStreamer->setUseAssemblerInfoForParsing(FlagToRestore);
 }
 
 void SPIRVAsmPrinter::emitFunctionHeader() {

llvm/test/MC/AsmParser/assembler-expressions-inlineasm.ll

@@ -1,16 +1,12 @@
-; RUN: not llc -mtriple=x86_64 %s -o /dev/null 2>&1 | FileCheck %s
-; RUN: llc -mtriple=x86_64 -no-integrated-as < %s | FileCheck %s --check-prefix=GAS
-; RUN: llc -mtriple=x86_64 -filetype=obj %s -o - | llvm-objdump -d - |  FileCheck %s --check-prefix=DISASM
+; RUN: not llc -mtriple x86_64-unknown-linux-gnu -o %t.s -filetype=asm %s 2>&1 | FileCheck %s
+; RUN: not llc -mtriple x86_64-unknown-linux-gnu -o %t.o -filetype=obj %s 2>&1 | FileCheck %s
 
-; GAS: nop;  .if . - foo==1; nop;.endif
+; Assembler-aware expression evaluation should be disabled in inline
+; assembly to prevent differences in behavior between object and
+; assembly output.
 
-; CHECK: <inline asm>:1:17: error: expected absolute expression
 
-; DISASM:      <main>:
-; DISASM-NEXT:   nop
-; DISASM-NEXT:   nop
-; DISASM-NEXT:   xorl %eax, %eax
-; DISASM-NEXT:   retq
+; CHECK: <inline asm>:1:17: error: expected absolute expression
 
 define i32 @main() local_unnamed_addr {
   tail call void asm sideeffect "foo: nop;  .if . - foo==1;  nop;.endif", "~{dirflag},~{fpsr},~{flags}"()

llvm/tools/llvm-mc/llvm-mc.cpp

@@ -569,6 +569,9 @@ int main(int argc, char **argv) {
       Str->initSections(true, *STI);
   }
 
+  // Use Assembler information for parsing.
+  Str->setUseAssemblerInfoForParsing(true);
+
   int Res = 1;
   bool disassemble = false;
   switch (Action) {

llvm/tools/llvm-ml/llvm-ml.cpp

@@ -428,6 +428,9 @@ int llvm_ml_main(int Argc, char **Argv, const llvm::ToolContext &) {
     Str->emitAssignment(Feat00Sym, MCConstantExpr::create(Feat00Flags, Ctx));
   }
 
+  // Use Assembler information for parsing.
+  Str->setUseAssemblerInfoForParsing(true);
+
   int Res = 1;
   if (InputArgs.hasArg(OPT_as_lex)) {
     // -as-lex; Lex only, and output a stream of tokens