[PATCH] D17786: [X86] Enable forwarding bool arguments in tail calls (PR26305)

[Hans Wennborg via llvm-commits]

hans added inline comments.

================
Comment at: lib/Target/X86/X86ISelLowering.cpp:3666
@@ +3665,3 @@
+
+    break;
+  }
----------------
rnk wrote:
> Maybe a `do { ... } while (false)` loop is appropriate here?
But then continue won't work?

================
Comment at: test/CodeGen/X86/tail-call-bools.ll:1
@@ +1,2 @@
+; RUN: llc -mtriple=i686-unknown-linux-gnu -o - %s | FileCheck %s
+
----------------
rnk wrote:
> Can you also run this in x86_64? The f_i32 guy will have to do `movss %rcx, %xmm0` or something.
> 
> Also, maybe `tail-call-casts.ll` is a better name for the test, since it's not all about bools.
My change doesn't affect tail call arguments passed in registers, so is mostly not relevant for x86_64.

I do want to look into x86_64 in a follow-up though. For bools, we currently generate:
```
movzbl  %dil, %edi
jmp     g_bool
```
i.e. we do make the tail call, but we don't recognize that the argument can be forwarded as-is. The float bitcast test will come in handy to check that we don't mess that up.


I've renamed the test case.


http://reviews.llvm.org/D17786