llvm-6502/lib/Target/SystemZ/SystemZSubtarget.cpp
Richard Sandiford 086791eca2 Add TargetLowering::prepareVolatileOrAtomicLoad
One unusual feature of the z architecture is that the result of a
previous load can be reused indefinitely for subsequent loads, even if
a cache-coherent store to that location is performed by another CPU.
A special serializing instruction must be used if you want to force
a load to be reattempted.

Since volatile loads are not supposed to be omitted in this way,
we should insert a serializing instruction before each such load.
The same goes for atomic loads.

The patch implements this at the IR->DAG boundary, in a similar way
to atomic fences.  It is a no-op for targets other than SystemZ.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196905 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-10 10:36:34 +00:00

68 lines
2.2 KiB
C++

//===-- 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"
#include "llvm/Support/Host.h"
#include "MCTargetDesc/SystemZMCTargetDesc.h"
#define GET_SUBTARGETINFO_TARGET_DESC
#define GET_SUBTARGETINFO_CTOR
#include "SystemZGenSubtargetInfo.inc"
using namespace llvm;
// Pin the vtabel to this file.
void SystemZSubtarget::anchor() {}
SystemZSubtarget::SystemZSubtarget(const std::string &TT,
const std::string &CPU,
const std::string &FS)
: SystemZGenSubtargetInfo(TT, CPU, FS), HasDistinctOps(false),
HasLoadStoreOnCond(false), HasHighWord(false), HasFPExtension(false),
HasFastSerialization(false), TargetTriple(TT) {
std::string CPUName = CPU;
if (CPUName.empty())
CPUName = "generic";
#if defined(__linux__) && defined(__s390x__)
if (CPUName == "generic")
CPUName = sys::getHostCPUName();
#endif
// 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;
}