[SystemZ] Add back end

This adds the actual lib/Target/SystemZ target files necessary to
implement the SystemZ target.  Note that at this point, the target
cannot yet be built since the configure bits are missing.  Those
will be provided shortly by a follow-on patch.

This version of the patch incorporates feedback from reviews by
Chris Lattner and Anton Korobeynikov.  Thanks to all reviewers!

Patch by Richard Sandiford.

llvm-svn: 181203

1 files changed, 56 insertions, 0 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZSubtarget.cpp b/llvm/lib/Target/SystemZ/SystemZSubtarget.cpp
new file mode 100644
index 00000000000..cfd3324aadb
--- /dev/null
+++ b/llvm/lib/Target/SystemZ/SystemZSubtarget.cpp
@@ -0,0 +1,56 @@
+//===-- SystemZSubtarget.cpp - SystemZ subtarget information --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "SystemZSubtarget.h"
+#include "llvm/IR/GlobalValue.h"
+
+#define GET_SUBTARGETINFO_TARGET_DESC
+#define GET_SUBTARGETINFO_CTOR
+#include "SystemZGenSubtargetInfo.inc"
+
+using namespace llvm;
+
+SystemZSubtarget::SystemZSubtarget(const std::string &TT,
+                                   const std::string &CPU,
+                                   const std::string &FS)
+  : SystemZGenSubtargetInfo(TT, CPU, FS), TargetTriple(TT) {
+  std::string CPUName = CPU;
+  if (CPUName.empty())
+    CPUName = "z10";
+
+  // Parse features string.
+  ParseSubtargetFeatures(CPUName, FS);
+}
+
+// Return true if GV binds locally under reloc model RM.
+static bool bindsLocally(const GlobalValue *GV, Reloc::Model RM) {
+  // For non-PIC, all symbols bind locally.
+  if (RM == Reloc::Static)
+    return true;
+
+  return GV->hasLocalLinkage() || !GV->hasDefaultVisibility();
+}
+
+bool SystemZSubtarget::isPC32DBLSymbol(const GlobalValue *GV,
+                                       Reloc::Model RM,
+                                       CodeModel::Model CM) const {
+  // PC32DBL accesses require the low bit to be clear.  Note that a zero
+  // value selects the default alignment and is therefore OK.
+  if (GV->getAlignment() == 1)
+    return false;
+
+  // For the small model, all locally-binding symbols are in range.
+  if (CM == CodeModel::Small)
+    return bindsLocally(GV, RM);
+
+  // For Medium and above, assume that the symbol is not within the 4GB range.
+  // Taking the address of locally-defined text would be OK, but that
+  // case isn't easy to detect.
+  return false;
+}