Added getReservedRegs().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34376 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 30 insertions, 9 deletions

diff --git a/lib/Target/PowerPC/PPCRegisterInfo.cpp b/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 3370c362f9..7553634066 100644
--- a/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -34,6 +34,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include <cstdlib>
 using namespace llvm;
@@ -338,6 +339,35 @@ PPCRegisterInfo::getCalleeSavedRegClasses() const {
                                Darwin32_CalleeSavedRegClasses;
 }
 
+// needsFP - Return true if the specified function should have a dedicated frame
+// pointer register.  This is true if the function has variable sized allocas or
+// if frame pointer elimination is disabled.
+//
+static bool needsFP(const MachineFunction &MF) {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  return NoFramePointerElim || MFI->hasVarSizedObjects();
+}
+
+BitVector PPCRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
+  BitVector Reserved(getNumRegs());
+  Reserved.set(PPC::R0);
+  Reserved.set(PPC::R1);
+  Reserved.set(PPC::LR);
+  // In Linux, r2 is reserved for the OS.
+  if (!Subtarget.isDarwin())
+    Reserved.set(PPC::R2);
+  // On PPC64, r13 is the thread pointer.  Never allocate this register.
+  // Note that this is overconservative, as it also prevents allocation of
+  // R31 when the FP is not needed.
+  if (Subtarget.isPPC64()) {
+    Reserved.set(PPC::R13);
+    Reserved.set(PPC::R31);
+  }
+  if (needsFP(MF))
+    Reserved.set(PPC::R31);
+  return Reserved;
+}
+
 /// foldMemoryOperand - PowerPC (like most RISC's) can only fold spills into
 /// copy instructions, turning them into load/store instructions.
 MachineInstr *PPCRegisterInfo::foldMemoryOperand(MachineInstr *MI,
@@ -398,15 +428,6 @@ MachineInstr *PPCRegisterInfo::foldMemoryOperand(MachineInstr *MI,
 // Stack Frame Processing methods
 //===----------------------------------------------------------------------===//
 
-// needsFP - Return true if the specified function should have a dedicated frame
-// pointer register.  This is true if the function has variable sized allocas or
-// if frame pointer elimination is disabled.
-//
-static bool needsFP(const MachineFunction &MF) {
-  const MachineFrameInfo *MFI = MF.getFrameInfo();
-  return NoFramePointerElim || MFI->hasVarSizedObjects();
-}
-
 // hasFP - Return true if the specified function actually has a dedicated frame
 // pointer register.  This is true if the function needs a frame pointer and has
 // a non-zero stack size.