From 9ccb76998f741a7d3f0f217392a783dfb99c6e87 Mon Sep 17 00:00:00 2001
From: Eli Bendersky <eliben@google.com>
Date: Tue, 15 Jan 2013 23:22:09 +0000
Subject: Optimize the memory usage of MC bundling, by creating a new type of
 fragment into which we can emit single instructions without fixups (which is
 most instructions). This is an optimization required because MCDataFragment
 is prety large (240 bytes on x64), with no change in functionality.

For large programs, this reduces memory usage overhead required for bundling
by 40%.

To make the code as palatable as possible, the MCEncodedFragment interface was
further fragmented (no pun intended) and MCEncodedFragmentWithFixups is used
as the interface to work against when the user expects fixups. MCDataFragment
and MCRelaxableFragment implement this interface, while the new
MCCompactEncodedInstFragment implements MCEncodeFragment.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@172572 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/MC/MCAssembler.cpp | 36 ++++++++++++++++++++++++++++++++++--
 1 file changed, 34 insertions(+), 2 deletions(-)

(limited to 'lib/MC/MCAssembler.cpp')

diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 5fdc57a..c51ddc8 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -38,6 +38,8 @@ STATISTIC(EmittedRelaxableFragments,
           "Number of emitted assembler fragments - relaxable");
 STATISTIC(EmittedDataFragments,
           "Number of emitted assembler fragments - data");
+STATISTIC(EmittedCompactEncodedInstFragments,
+          "Number of emitted assembler fragments - compact encoded inst");
 STATISTIC(EmittedAlignFragments,
           "Number of emitted assembler fragments - align");
 STATISTIC(EmittedFillFragments,
@@ -222,6 +224,11 @@ MCEncodedFragment::~MCEncodedFragment() {
 
 /* *** */
 
+MCEncodedFragmentWithFixups::~MCEncodedFragmentWithFixups() {
+}
+
+/* *** */
+
 MCSectionData::MCSectionData() : Section(0) {}
 
 MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
@@ -388,6 +395,7 @@ uint64_t MCAssembler::computeFragmentSize(const MCAsmLayout &Layout,
   switch (F.getKind()) {
   case MCFragment::FT_Data:
   case MCFragment::FT_Relaxable:
+  case MCFragment::FT_CompactEncodedInst:
     return cast<MCEncodedFragment>(F).getContents().size();
   case MCFragment::FT_Fill:
     return cast<MCFillFragment>(F).getSize();
@@ -570,6 +578,11 @@ static void writeFragment(const MCAssembler &Asm, const MCAsmLayout &Layout,
     writeFragmentContents(F, OW);
     break;
 
+  case MCFragment::FT_CompactEncodedInst:
+    ++stats::EmittedCompactEncodedInstFragments;
+    writeFragmentContents(F, OW);
+    break;
+
   case MCFragment::FT_Fill: {
     ++stats::EmittedFillFragments;
     MCFillFragment &FF = cast<MCFillFragment>(F);
@@ -742,9 +755,10 @@ void MCAssembler::Finish() {
   for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
     for (MCSectionData::iterator it2 = it->begin(),
            ie2 = it->end(); it2 != ie2; ++it2) {
-      MCEncodedFragment *F = dyn_cast<MCEncodedFragment>(it2);
+      MCEncodedFragmentWithFixups *F =
+        dyn_cast<MCEncodedFragmentWithFixups>(it2);
       if (F) {
-        for (MCEncodedFragment::fixup_iterator it3 = F->fixup_begin(),
+        for (MCEncodedFragmentWithFixups::fixup_iterator it3 = F->fixup_begin(),
              ie3 = F->fixup_end(); it3 != ie3; ++it3) {
           MCFixup &Fixup = *it3;
           uint64_t FixedValue = handleFixup(Layout, *F, Fixup);
@@ -954,6 +968,8 @@ void MCFragment::dump() {
   switch (getKind()) {
   case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
   case MCFragment::FT_Data:  OS << "MCDataFragment"; break;
+  case MCFragment::FT_CompactEncodedInst:
+    OS << "MCCompactEncodedInstFragment"; break;
   case MCFragment::FT_Fill:  OS << "MCFillFragment"; break;
   case MCFragment::FT_Relaxable:  OS << "MCRelaxableFragment"; break;
   case MCFragment::FT_Org:   OS << "MCOrgFragment"; break;
@@ -1001,6 +1017,19 @@ void MCFragment::dump() {
     }
     break;
   }
+  case MCFragment::FT_CompactEncodedInst: {
+    const MCCompactEncodedInstFragment *CEIF =
+      cast<MCCompactEncodedInstFragment>(this);
+    OS << "\n       ";
+    OS << " Contents:[";
+    const SmallVectorImpl<char> &Contents = CEIF->getContents();
+    for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
+      if (i) OS << ",";
+      OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
+    }
+    OS << "] (" << Contents.size() << " bytes)";
+    break;
+  }
   case MCFragment::FT_Fill:  {
     const MCFillFragment *FF = cast<MCFillFragment>(this);
     OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
@@ -1094,7 +1123,9 @@ void MCAssembler::dump() {
 
 // anchors for MC*Fragment vtables
 void MCEncodedFragment::anchor() { }
+void MCEncodedFragmentWithFixups::anchor() { }
 void MCDataFragment::anchor() { }
+void MCCompactEncodedInstFragment::anchor() { }
 void MCRelaxableFragment::anchor() { }
 void MCAlignFragment::anchor() { }
 void MCFillFragment::anchor() { }
@@ -1102,3 +1133,4 @@ void MCOrgFragment::anchor() { }
 void MCLEBFragment::anchor() { }
 void MCDwarfLineAddrFragment::anchor() { }
 void MCDwarfCallFrameFragment::anchor() { }
+
-- 
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