[PATCH] D18680: ARM, AArch64, X86: Check preserved registers for tail calls.

[Matthias Braun via llvm-commits]

MatzeB added inline comments.

================
Comment at: lib/CodeGen/TargetRegisterInfo.cpp:395
@@ +394,3 @@
+  for (unsigned I = 0; I < N; ++I)
+    if ((mask0[I] & mask1[I]) != mask0[I])
+      return false;
----------------
rengolin wrote:
> IIUC, you need to check that all reserved registers on the left are also on the right, but not necessarily all on the right to be on the left, right? In that case, this check would be too restrictive, mostly matching recursive tail calls only, no?
That's what the check is doing, isn't it?

| Bit0 | Bit1 | Bit0&Bit1 == Bit0
| 0    |  0/1 |            1
| 1    |   0  |            0
| 1    |   1  |            1

Is there a clearer way to write the code?


Repository:
  rL LLVM

http://reviews.llvm.org/D18680