Allow {e,r}bp as the target of {read,write}_register.

This patch allows the read_register and write_register intrinsics to
read/write the RBP/EBP registers on X86 iff the targeted register is
the frame pointer for the containing function.

Differential Revision: http://reviews.llvm.org/D10977

llvm-svn: 241827

1 files changed, 24 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 7360d90ef3f..74e5dd62ccb 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -16262,14 +16262,36 @@ SDValue X86TargetLowering::LowerFRAMEADDR(SDValue Op, SelectionDAG &DAG) const {
 
 // FIXME? Maybe this could be a TableGen attribute on some registers and
 // this table could be generated automatically from RegInfo.
-unsigned X86TargetLowering::getRegisterByName(const char* RegName,
-                                              EVT VT) const {
+unsigned X86TargetLowering::getRegisterByName(const char* RegName, EVT VT,
+                                              SelectionDAG &DAG) const {
+  const TargetFrameLowering &TFI = *Subtarget->getFrameLowering();
+  const MachineFunction &MF = DAG.getMachineFunction();
+
   unsigned Reg = StringSwitch<unsigned>(RegName)
                        .Case("esp", X86::ESP)
                        .Case("rsp", X86::RSP)
+                       .Case("ebp", X86::EBP)
+                       .Case("rbp", X86::RBP)
                        .Default(0);
+
+  if (Reg == X86::EBP || Reg == X86::RBP) {
+    if (!TFI.hasFP(MF))
+      report_fatal_error("register " + StringRef(RegName) +
+                         " is allocatable: function has no frame pointer");
+#ifndef NDEBUG
+    else {
+      const X86RegisterInfo *RegInfo = Subtarget->getRegisterInfo();
+      unsigned FrameReg =
+          RegInfo->getPtrSizedFrameRegister(DAG.getMachineFunction());
+      assert((FrameReg == X86::EBP || FrameReg == X86::RBP) &&
+             "Invalid Frame Register!");
+    }
+#endif
+  }
+
   if (Reg)
     return Reg;
+
   report_fatal_error("Invalid register name global variable");
 }