[ARM] Emmit data symbol for constant pool data

[dnsampaio]

Summary

The ARM elf emitter would omit printing data symbol when constant data. This patch overrides the emitFill method as to enforce that the symbol is correctly printed.

[olista01]

lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

1485

Why can't we just call EmitDataMappingSymbol, like EmitBytes does?

test/CodeGen/ARM/CheckDataSymbol.ll

1 ↗

(On Diff #167785)

I don't think this test is necessary, since this can be tested with an assembly file.

test/CodeGen/ARM/CheckDataSymbol.s

18

This test can be reduced greatly, to something like this:

.text
nop
.zero 4

[dnsampaio]

lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

1485

Indeed it can.

[dnsampaio]

Simplified tests. Using the standard function for emitting data symbols, if required.

[olista01]

test/CodeGen/ARM/CheckDataSymbol.s

1

We can't use clang in LLVM tests (LLVM can be built without clang), this should use llvm-mc instead. Also, this should be in tests/MC/ARM, not tests/CodeGen/ARM, since it's testing stuff in the MC layer.

[dnsampaio]

Updated test to use llvm-mc instead of clang.

[olista01]

LGTM with one nit.

test/MC/ARM/CheckDataSymbol.s

1 ↗

(On Diff #167912)

The -arm-implicit-it=thumb option isn't needed here.

lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp

public:
   void emitPersonality(const MCSymbol *Per);
   void emitPersonalityIndex(unsigned index);
   void emitHandlerData();
   void emitSetFP(unsigned NewFpReg, unsigned NewSpReg, int64_t Offset = 0);
   void emitMovSP(unsigned Reg, int64_t Offset = 0);
   void emitPad(int64_t Offset);
   void emitRegSave(const SmallVectorImpl<unsigned> &RegList, bool isVector);
   void emitUnwindRaw(int64_t Offset, const SmallVectorImpl<uint8_t> &Opcodes);
+  void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
+                SMLoc Loc) override {
+    EmitDataMappingSymbol();
+    MCObjectStreamer::emitFill(NumBytes, FillValue, Loc);
+  }
 
   void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
     LastMappingSymbols[getCurrentSection().first] = std::move(LastEMSInfo);
     MCELFStreamer::ChangeSection(Section, Subsection);
     auto LastMappingSymbol = LastMappingSymbols.find(Section);
     if (LastMappingSymbol != LastMappingSymbols.end()) {
       LastEMSInfo = std::move(LastMappingSymbol->second);
       return;
void ARMELFStreamer::emitUnwindRaw(int64_t Offset,
                                    const SmallVectorImpl<uint8_t> &Opcodes) {
   FlushPendingOffset();
   SPOffset = SPOffset - Offset;
   UnwindOpAsm.EmitRaw(Opcodes);
 }
 
 namespace llvm {
 
 MCTargetStreamer *createARMTargetAsmStreamer(MCStreamer &S,
                                              formatted_raw_ostream &OS,
                                              MCInstPrinter *InstPrint,
                                              bool isVerboseAsm) {
   return new ARMTargetAsmStreamer(S, OS, *InstPrint, isVerboseAsm);
 }
 
 MCTargetStreamer *createARMNullTargetStreamer(MCStreamer &S) {
   return new ARMTargetStreamer(S);

test/CodeGen/ARM/CheckDataSymbol.s

+# RUN: clang -c -target arm-arm-none-eabi -mcpu=cortex-a9 -O2 -mthumb %s -o - | llvm-readobj -s -t - | FileCheck %s
+# CHECK:     Name: $d.1 ({{[1-9][0-9]+}})
+# CHECK-NEXT:     Value: 0x4
+# CHECK-NEXT:     Size: 0
+# CHECK-NEXT:     Binding: Local (0x0)
+# CHECK-NEXT:     Type: None (0x0)
+# CHECK-NEXT:     Other: 0
+# CHECK-NEXT:     Section: .text (0x2)
+# CHECK-NEXT:   }
+
+.text
+nop
+.zero 4