ARM, AArch64, X86: Check preserved registers for tail calls.

We can only perform a tail call to a callee that preserves all the
registers that the caller needs to preserve.

This situation happens with calling conventions like preserver_mostcc or
cxx_fast_tls. It was explicitely handled for fast_tls and failing for
preserve_most. This patch generalizes the check to any calling
convention.

Related to rdar://24207743

Differential Revision: http://reviews.llvm.org/D18680

llvm-svn: 265329

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/TargetRegisterInfo.cpp b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
index 0a7042ac3db..fc88629b5c8 100644
--- a/llvm/lib/CodeGen/TargetRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
@@ -388,6 +388,15 @@ bool TargetRegisterInfo::needsStackRealignment(
   return false;
 }
 
+bool TargetRegisterInfo::regmaskSubsetEqual(const uint32_t *mask0,
+                                            const uint32_t *mask1) const {
+  unsigned N = (getNumRegs()+31) / 32;
+  for (unsigned I = 0; I < N; ++I)
+    if ((mask0[I] & mask1[I]) != mask0[I])
+      return false;
+  return true;
+}
+
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void
 TargetRegisterInfo::dumpReg(unsigned Reg, unsigned SubRegIndex,