Support: add Windows ARM EH data structures

Introduce the support structures necessary to deal with the Windows ARM EH data.
These definitions are extremely aggressive about assertions to aid future use
for generation of the entries and subsequent decoding.

The names for the various fields are meant to reflect the names used by the
Visual Studio toolchain to aid communication.

Due to the complexity in reading a few of the values, there are a couple of
additional utility functions to decode the information.

In general, there are two ways to encode the unwinding information:
- packed, which places the data inline into the
  _IMAGE_ARM_RUNTIME_FUNCTION_ENTRY structure.
- unpacked, which places the data into auxiliary structures placed into the
  .xdata section.

The set of structures allow reading of data in either encoding, with the minor
caveat that epilogue scopes need to be decoded manually by constructing the
structure from the data returned by the RuntimeFunction structure.

These definitions are meant for read-only access at the current point as the
first use of them will be to decode the exception information.

llvm-svn: 209998

2 files changed, 39 insertions, 0 deletions

diff --git a/llvm/lib/Support/ARMWinEH.cpp b/llvm/lib/Support/ARMWinEH.cpp
new file mode 100644
index 00000000000..03c150f1150
--- /dev/null
+++ b/llvm/lib/Support/ARMWinEH.cpp
@@ -0,0 +1,38 @@
+//===-- ARMWinEH.cpp - Windows on ARM EH Support Functions ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/ARMWinEH.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+namespace ARM {
+namespace WinEH {
+std::pair<uint16_t, uint32_t> SavedRegisterMask(const RuntimeFunction &RF) {
+  uint8_t NumRegisters = RF.Reg();
+  uint8_t RegistersVFP = RF.R();
+  uint8_t LinkRegister = RF.L();
+  uint8_t ChainedFrame = RF.C();
+
+  uint16_t GPRMask = (ChainedFrame << 11) | (LinkRegister << 14);
+  uint32_t VFPMask = 0;
+
+  if (RegistersVFP)
+    VFPMask |= (((1 << ((NumRegisters + 1) % 8)) - 1) << 8);
+  else
+    GPRMask |= (((1 << (NumRegisters + 1)) - 1) << 4);
+
+  if (PrologueFolding(RF))
+    GPRMask |= (((1 << (NumRegisters + 1)) - 1) << (~RF.StackAdjust() & 0x3));
+
+  return std::make_pair(GPRMask, VFPMask);
+}
+}
+}
+}
+
diff --git a/llvm/lib/Support/CMakeLists.txt b/llvm/lib/Support/CMakeLists.txt
index b4c674d32e2..7f93a6c5958 100644
--- a/llvm/lib/Support/CMakeLists.txt
+++ b/llvm/lib/Support/CMakeLists.txt
@@ -3,6 +3,7 @@ add_llvm_library(LLVMSupport
   APInt.cpp
   APSInt.cpp
   ARMBuildAttrs.cpp
+  ARMWinEH.cpp
   Allocator.cpp
   BlockFrequency.cpp
   BranchProbability.cpp