[COFF][X86_64] Put jump table in .rdata for Windows

Put jump table in .rdata for Windows to align with that for Linux.
It can avoid loading the same code page into I$ and D$ simultaneously
and thus favor performance.

Differential Revision: https://reviews.llvm.org/D144701

1 files changed, 17 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 9852ffe..b78a4d2 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -71,6 +71,10 @@
 using namespace llvm;
 using namespace dwarf;
 
+static cl::opt<bool> JumpTableInFunctionSection(
+    "jumptable-in-function-section", cl::Hidden, cl::init(false),
+    cl::desc("Putting Jump Table in function section"));
+
 static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
                              StringRef &Section) {
   SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
@@ -1777,6 +1781,19 @@ MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
       COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 }
 
+bool TargetLoweringObjectFileCOFF::shouldPutJumpTableInFunctionSection(
+    bool UsesLabelDifference, const Function &F) const {
+  if (TM->getTargetTriple().getArch() == Triple::x86_64) {
+    if (!JumpTableInFunctionSection) {
+      // We can always create relative relocations, so use another section
+      // that can be marked non-executable.
+      return false;
+    }
+  }
+  return TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection(
+    UsesLabelDifference, F);
+}
+
 void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
                                                       Module &M) const {
   emitLinkerDirectives(Streamer, M);