Introduce new @llvm.get.dynamic.area.offset.i{32, 64} intrinsics.

The @llvm.get.dynamic.area.offset.* intrinsic family is used to get the offset
from native stack pointer to the address of the most recent dynamic alloca on
the caller's stack. These intrinsics are intendend for use in combination with
@llvm.stacksave and @llvm.restore to get a pointer to the most recent dynamic
alloca. This is useful, for example, for AddressSanitizer's stack unpoisoning
routines.

Patch by Max Ostapenko.

Differential Revision: http://reviews.llvm.org/D14983

llvm-svn: 254404

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index 6d53f876c06..934bdf62241 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -430,6 +430,27 @@ void PPCRegisterInfo::lowerDynamicAlloc(MachineBasicBlock::iterator II) const {
   MBB.erase(II);
 }
 
+void PPCRegisterInfo::lowerDynamicAreaOffset(
+    MachineBasicBlock::iterator II) const {
+  // Get the instruction.
+  MachineInstr &MI = *II;
+  // Get the instruction's basic block.
+  MachineBasicBlock &MBB = *MI.getParent();
+  // Get the basic block's function.
+  MachineFunction &MF = *MBB.getParent();
+  // Get the frame info.
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+  const PPCSubtarget &Subtarget = MF.getSubtarget<PPCSubtarget>();
+  // Get the instruction info.
+  const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
+
+  unsigned maxCallFrameSize = MFI->getMaxCallFrameSize();
+  DebugLoc dl = MI.getDebugLoc();
+  BuildMI(MBB, II, dl, TII.get(PPC::LI), MI.getOperand(0).getReg())
+      .addImm(maxCallFrameSize);
+  MBB.erase(II);
+}
+
 /// lowerCRSpilling - Generate the code for spilling a CR register. Instead of
 /// reserving a whole register (R0), we scrounge for one here. This generates
 /// code like this:
@@ -754,6 +775,11 @@ PPCRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // Get the instruction opcode.
   unsigned OpC = MI.getOpcode();
 
+  if ((OpC == PPC::DYNAREAOFFSET || OpC == PPC::DYNAREAOFFSET8)) {
+    lowerDynamicAreaOffset(II);
+    return;
+  }
+
   // Special case for dynamic alloca.
   if (FPSI && FrameIndex == FPSI &&
       (OpC == PPC::DYNALLOC || OpC == PPC::DYNALLOC8)) {