[XRay] ARM 32-bit no-Thumb support in Clang

[rSerge]

Summary

Just a test for now, adapted from x86_64 tests of XRay.
This is one of 3 commits to different repositories of XRay ARM port. The other 2 are:

1. https://reviews.llvm.org/D23931 (LLVM)
2. https://reviews.llvm.org/D23933 (compiler-rt)

[rengolin]

If this works without the other two patches, it's reasonably unrelated and harmless, and should be ok as soon as the other two patches are approved.

Not because it's wrong, just because we don't want to advertise features in Clang that yet don't exist in LLVM. :)

[dberris]

Concur 100% with @rengolin here -- please land after the LLVM changes land. :)

[rSerge]

I don't have commit access rights. Could someone commit?

[dberris]

Landing this one now.

[dberris]

This has been landed as rL280889.

[dberris]

Reverted in rL280968 -- we should resolve D23931 before attempting to land again.

[dberris]

See comments in D23931 for more details.

[rSerge]

Fixed patch file format.

test/CodeGen/xray-attributes-supported-arm.cpp

+// RUN: %clang_cc1 %s -fxray-instrument -std=c++11 -x c++ -emit-llvm -o - -triple arm-unknown-linux-gnu | FileCheck %s
+
+// Make sure that the LLVM attribute for XRay-annotated functions do show up.
+[[clang::xray_always_instrument]] void foo() {
+// CHECK: define void @_Z3foov() #0
+};
+
+[[clang::xray_never_instrument]] void bar() {
+// CHECK: define void @_Z3barv() #1
+};
+
+// CHECK: #0 = {{.*}}"function-instrument"="xray-always"
+// CHECK: #1 = {{.*}}"function-instrument"="xray-never"