[X86] Add new calling convention that guarantees tail call optimization
When the target option GuaranteedTailCallOpt is specified, calls with
the fastcc calling convention will be transformed into tail calls if
they are in tail position. This diff adds a new calling convention,
tailcc, currently supported only on X86, which behaves the same way as
fastcc, except that the GuaranteedTailCallOpt flag does not need to
enabled in order to enable tail call optimization.
Patch by Dwight Guth <dwight.guth@runtimeverification.com>!
Reviewed By: lebedev.ri, paquette, rnk
Differential Revision: https://reviews.llvm.org/D67855
llvm-svn: 373976
diff --git a/llvm/docs/CodeGenerator.rst b/llvm/docs/CodeGenerator.rst
index 343b987..75330a5 100644
--- a/llvm/docs/CodeGenerator.rst
+++ b/llvm/docs/CodeGenerator.rst
@@ -2068,12 +2068,12 @@
and PowerPC if:
* Caller and callee have the calling convention ``fastcc``, ``cc 10`` (GHC
- calling convention) or ``cc 11`` (HiPE calling convention).
+ calling convention), ``cc 11`` (HiPE calling convention), or ``tailcc``.
* The call is a tail call - in tail position (ret immediately follows call and
ret uses value of call or is void).
-* Option ``-tailcallopt`` is enabled.
+* Option ``-tailcallopt`` is enabled or the calling convention is ``tailcc``.
* Platform-specific constraints are met.