[ms-cxxabi] Add a new calling convention that swaps 'this' and 'sret'
MSVC always places the 'this' parameter for a method first. The
implicit 'sret' pointer for methods always comes second. We already
implement this for __thiscall by putting sret parameters on the stack,
but __cdecl methods require putting both parameters on the stack in
opposite order.
Using a special calling convention allows frontends to keep the sret
parameter first, which avoids breaking lots of assumptions in LLVM and
Clang.
Fixes PR15768 with the corresponding change in Clang.
Reviewers: ributzka, majnemer
Differential Revision: http://llvm-reviews.chandlerc.com/D2663
llvm-svn: 200561
diff --git a/llvm/docs/BitCodeFormat.rst b/llvm/docs/BitCodeFormat.rst
index 38b4010..4c1c94a 100644
--- a/llvm/docs/BitCodeFormat.rst
+++ b/llvm/docs/BitCodeFormat.rst
@@ -746,6 +746,8 @@
* ``arm_apcscc``: code 66
* ``arm_aapcscc``: code 67
* ``arm_aapcs_vfpcc``: code 68
+ * ``x86_thiscallcc``: code 70
+ * ``x86_cdeclmethodcc``: code 80
* isproto*: Non-zero if this entry represents a declaration rather than a
definition
diff --git a/llvm/docs/CodeGenerator.rst b/llvm/docs/CodeGenerator.rst
index b89d2f4..d7d98bc 100644
--- a/llvm/docs/CodeGenerator.rst
+++ b/llvm/docs/CodeGenerator.rst
@@ -2145,6 +2145,10 @@
others via stack. Callee is responsible for stack cleaning. This convention is
used by MSVC by default for methods in its ABI (CC ID = 70).
+* **X86_CDeclMethod** --- Identical to the standard x86_32 C calling convention,
+ except that an sret paramter, if present, is placed on the stack after the
+ second parameter, which must an integer or pointer. (CC ID = 80).
+
.. _X86 addressing mode:
Representing X86 addressing modes in MachineInstrs