[ARM] [MC] Refactor the constant pool classes

ARMTargetStreamer implements ConstantPool and AssmeblerConstantPools
to keep track of assembler-generated constant pools that are used for
ldr-pseudo.

When implementing ldr-pseudo for AArch64, these two classes can be reused.
So this patch factors them out from ARM target to the general MC lib.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211198 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 96 insertions, 0 deletions

diff --git a/lib/MC/CMakeLists.txt b/lib/MC/CMakeLists.txt
index 6a384c1a8e..78bd8c4ba1 100644
--- a/lib/MC/CMakeLists.txt
+++ b/lib/MC/CMakeLists.txt
@@ -1,4 +1,5 @@
 add_llvm_library(LLVMMC
+  ConstantPools.cpp
   ELFObjectWriter.cpp
   MCAsmBackend.cpp
   MCAsmInfo.cpp
diff --git a/lib/MC/ConstantPools.cpp b/lib/MC/ConstantPools.cpp
new file mode 100644
index 0000000000..f979dad47d
--- /dev/null
+++ b/lib/MC/ConstantPools.cpp
@@ -0,0 +1,95 @@
+//===- ConstantPools.cpp - ConstantPool class --*- C++ -*---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the ConstantPool and  AssemblerConstantPools classes.
+//
+//===----------------------------------------------------------------------===//
+#include "llvm/ADT/MapVector.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCStreamer.h"
+#include "llvm/MC/ConstantPools.h"
+
+using namespace llvm;
+//
+// ConstantPool implementation
+//
+// Emit the contents of the constant pool using the provided streamer.
+void ConstantPool::emitEntries(MCStreamer &Streamer) {
+  if (Entries.empty())
+    return;
+  Streamer.EmitCodeAlignment(4); // align to 4-byte address
+  Streamer.EmitDataRegion(MCDR_DataRegion);
+  for (EntryVecTy::const_iterator I = Entries.begin(), E = Entries.end();
+       I != E; ++I) {
+    Streamer.EmitLabel(I->first);
+    Streamer.EmitValue(I->second, 4);
+  }
+  Streamer.EmitDataRegion(MCDR_DataRegionEnd);
+  Entries.clear();
+}
+
+const MCExpr *ConstantPool::addEntry(const MCExpr *Value, MCContext &Context) {
+  MCSymbol *CPEntryLabel = Context.CreateTempSymbol();
+
+  Entries.push_back(std::make_pair(CPEntryLabel, Value));
+  return MCSymbolRefExpr::Create(CPEntryLabel, Context);
+}
+
+bool ConstantPool::empty() { return Entries.empty(); }
+
+//
+// AssemblerConstantPools implementation
+//
+ConstantPool *
+AssemblerConstantPools::getConstantPool(const MCSection *Section) {
+  ConstantPoolMapTy::iterator CP = ConstantPools.find(Section);
+  if (CP == ConstantPools.end())
+    return nullptr;
+
+  return &CP->second;
+}
+
+ConstantPool &
+AssemblerConstantPools::getOrCreateConstantPool(const MCSection *Section) {
+  return ConstantPools[Section];
+}
+
+static void emitConstantPool(MCStreamer &Streamer, const MCSection *Section,
+                             ConstantPool &CP) {
+  if (!CP.empty()) {
+    Streamer.SwitchSection(Section);
+    CP.emitEntries(Streamer);
+  }
+}
+
+void AssemblerConstantPools::emitAll(MCStreamer &Streamer) {
+  // Dump contents of assembler constant pools.
+  for (ConstantPoolMapTy::iterator CPI = ConstantPools.begin(),
+                                   CPE = ConstantPools.end();
+       CPI != CPE; ++CPI) {
+    const MCSection *Section = CPI->first;
+    ConstantPool &CP = CPI->second;
+
+    emitConstantPool(Streamer, Section, CP);
+  }
+}
+
+void AssemblerConstantPools::emitForCurrentSection(MCStreamer &Streamer) {
+  const MCSection *Section = Streamer.getCurrentSection().first;
+  if (ConstantPool *CP = getConstantPool(Section)) {
+    emitConstantPool(Streamer, Section, *CP);
+  }
+}
+
+const MCExpr *AssemblerConstantPools::addEntry(MCStreamer &Streamer,
+                                               const MCExpr *Expr) {
+  const MCSection *Section = Streamer.getCurrentSection().first;
+  return getOrCreateConstantPool(Section).addEntry(Expr, Streamer.getContext());
+}