Fall back to the selection dag isel to select tail calls.

This shouldn't affect codegen for -O0 compiles as tail call markers are not
emitted in unoptimized compiles.  Testing with the external/internal nightly
test suite reveals no change in compile time performance.  Testing with -O1,
-O2 and -O3 with fast-isel enabled did not cause any compile-time or
execution-time failures.  All tests were performed on my x86 machine.
I'll monitor our arm testers to ensure no regressions occur there.

In an upcoming clang patch I will be marking the objc_autoreleaseReturnValue
and objc_retainAutoreleaseReturnValue as tail calls unconditionally.  While
it's theoretically true that this is just an optimization, it's an
optimization that we very much want to happen even at -O0, or else ARC
applications become substantially harder to debug.

Part of rdar://12553082

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169796 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 3 deletions

diff --git a/test/CodeGen/X86/tailcall-fastisel.ll b/test/CodeGen/X86/tailcall-fastisel.ll
index 7f92af4dca..9962d71988 100644
--- a/test/CodeGen/X86/tailcall-fastisel.ll
+++ b/test/CodeGen/X86/tailcall-fastisel.ll
@@ -1,12 +1,11 @@
-; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel | not grep TAILCALL
-
-; Fast-isel shouldn't attempt to cope with tail calls.
+; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel -fast-isel-abort | FileCheck %s
 
 %0 = type { i64, i32, i8* }
 
 define fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 %arg1) nounwind {
 fail:                                             ; preds = %entry
   %tmp20 = tail call fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 undef) ; <i8*> [#uses=1]
+; CHECK: jmp "_visit_array_aux<`Reference>" ## TAILCALL
   ret i8* %tmp20
 }