[MC] Delete MCCodePadder

D34393 added MCCodePadder as an infrastructure for padding code with
NOP instructions. It lacked tests and was not being worked on since
then.

Intel has now worked on an assembler patch to mitigate performance loss
after applying microcode update for the Jump Conditional Code Erratum.

https://www.intel.com/content/www/us/en/support/articles/000055650/processors.html

This new patch shares similarity with MCCodePadder, but has a concrete
use case in mind and is being actively developed. The infrastructure it
introduces can potentially be used for general performance improvement
via alignment. Delete the unused MCCodePadder so that people can develop
the new feature from a clean state.

Reviewed By: jyknight, skan

Differential Revision: https://reviews.llvm.org/D71106

1 files changed, 0 insertions, 31 deletions

diff --git a/llvm/lib/MC/MCAssembler.cpp b/llvm/lib/MC/MCAssembler.cpp
index cf42fe85b8e..2e9cfc73cf4 100644
--- a/llvm/lib/MC/MCAssembler.cpp
+++ b/llvm/lib/MC/MCAssembler.cpp
@@ -68,10 +68,6 @@ STATISTIC(FragmentLayouts, "Number of fragment layouts");
 STATISTIC(ObjectBytes, "Number of emitted object file bytes");
 STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
 STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
-STATISTIC(PaddingFragmentsRelaxations,
-          "Number of Padding Fragments relaxations");
-STATISTIC(PaddingFragmentsBytes,
-          "Total size of all padding from adding Fragments");
 
 } // end namespace stats
 } // end anonymous namespace
@@ -313,9 +309,6 @@ uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
   case MCFragment::FT_LEB:
     return cast<MCLEBFragment>(F).getContents().size();
 
-  case MCFragment::FT_Padding:
-    return cast<MCPaddingFragment>(F).getSize();
-
   case MCFragment::FT_SymbolId:
     return 4;
 
@@ -612,13 +605,6 @@ static void writeFragment(raw_ostream &OS, const MCAssembler &Asm,
     break;
   }
 
-  case MCFragment::FT_Padding: {
-    if (!Asm.getBackend().writeNopData(OS, FragmentSize))
-      report_fatal_error("unable to write nop sequence of " +
-                         Twine(FragmentSize) + " bytes");
-    break;
-  }
-
   case MCFragment::FT_SymbolId: {
     const MCSymbolIdFragment &SF = cast<MCSymbolIdFragment>(F);
     support::endian::write<uint32_t>(OS, SF.getSymbol()->getIndex(), Endian);
@@ -935,20 +921,6 @@ bool MCAssembler::relaxInstruction(MCAsmLayout &Layout,
   return true;
 }
 
-bool MCAssembler::relaxPaddingFragment(MCAsmLayout &Layout,
-                                       MCPaddingFragment &PF) {
-  assert(getBackendPtr() && "Expected assembler backend");
-  uint64_t OldSize = PF.getSize();
-  if (!getBackend().relaxFragment(&PF, Layout))
-    return false;
-  uint64_t NewSize = PF.getSize();
-
-  ++stats::PaddingFragmentsRelaxations;
-  stats::PaddingFragmentsBytes += NewSize;
-  stats::PaddingFragmentsBytes -= OldSize;
-  return true;
-}
-
 bool MCAssembler::relaxLEB(MCAsmLayout &Layout, MCLEBFragment &LF) {
   uint64_t OldSize = LF.getContents().size();
   int64_t Value;
@@ -1085,9 +1057,6 @@ bool MCAssembler::layoutSectionOnce(MCAsmLayout &Layout, MCSection &Sec) {
     case MCFragment::FT_LEB:
       RelaxedFrag = relaxLEB(Layout, *cast<MCLEBFragment>(I));
       break;
-    case MCFragment::FT_Padding:
-      RelaxedFrag = relaxPaddingFragment(Layout, *cast<MCPaddingFragment>(I));
-      break;
     case MCFragment::FT_CVInlineLines:
       RelaxedFrag =
           relaxCVInlineLineTable(Layout, *cast<MCCVInlineLineTableFragment>(I));