[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, 1 insertions, 24 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 0290eee82b7..a8e8d3f813d 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -85,7 +85,6 @@
 #include "llvm/IR/Type.h"
 #include "llvm/IR/Value.h"
 #include "llvm/MC/MCAsmInfo.h"
-#include "llvm/MC/MCCodePadder.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDirectives.h"
 #include "llvm/MC/MCDwarf.h"
@@ -2923,21 +2922,6 @@ static void emitBasicBlockLoopComments(const MachineBasicBlock &MBB,
   PrintChildLoopComment(OS, Loop, AP.getFunctionNumber());
 }
 
-void AsmPrinter::setupCodePaddingContext(const MachineBasicBlock &MBB,
-                                         MCCodePaddingContext &Context) const {
-  assert(MF != nullptr && "Machine function must be valid");
-  bool OptForSize = MF->getFunction().hasOptSize() ||
-                    llvm::shouldOptimizeForSize(&MBB, PSI, MBFI);
-  Context.IsPaddingActive = !MF->hasInlineAsm() &&
-                            !OptForSize &&
-                            TM.getOptLevel() != CodeGenOpt::None;
-  Context.IsBasicBlockReachableViaFallthrough =
-      std::find(MBB.pred_begin(), MBB.pred_end(), MBB.getPrevNode()) !=
-      MBB.pred_end();
-  Context.IsBasicBlockReachableViaBranch =
-      MBB.pred_size() > 0 && !isBlockOnlyReachableByFallthrough(&MBB);
-}
-
 /// EmitBasicBlockStart - This method prints the label for the specified
 /// MachineBasicBlock, an alignment (if present) and a comment describing
 /// it if appropriate.
@@ -2954,9 +2938,6 @@ void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock &MBB) {
   const Align Alignment = MBB.getAlignment();
   if (Alignment != Align::None())
     EmitAlignment(Alignment);
-  MCCodePaddingContext Context;
-  setupCodePaddingContext(MBB, Context);
-  OutStreamer->EmitCodePaddingBasicBlockStart(Context);
 
   // If the block has its address taken, emit any labels that were used to
   // reference the block.  It is possible that there is more than one label
@@ -3004,11 +2985,7 @@ void AsmPrinter::EmitBasicBlockStart(const MachineBasicBlock &MBB) {
   }
 }
 
-void AsmPrinter::EmitBasicBlockEnd(const MachineBasicBlock &MBB) {
-  MCCodePaddingContext Context;
-  setupCodePaddingContext(MBB, Context);
-  OutStreamer->EmitCodePaddingBasicBlockEnd(Context);
-}
+void AsmPrinter::EmitBasicBlockEnd(const MachineBasicBlock &MBB) {}
 
 void AsmPrinter::EmitVisibility(MCSymbol *Sym, unsigned Visibility,
                                 bool IsDefinition) const {