[XRay][CodeGen][PowerPC] Fix tail exit codegen for XRay in PPC

Summary:
This fixes code-gen for XRay in PPC. The regression wasn't caught by
codegen tests  which we add in this change.

What happened was the following:

- For tail exits, we used to unconditionally prepend the returns/exits
  with a pseudo-instruction that gets lowered to the instrumentation
  sled (and leave the actual return/exit instruction as-is).
- Changes to the XRay instrumentation pass caused the tail exits to
  suddenly also emit the tail exit pseudo-instruction, since the check
  for whether a return instruction was also a call instruction meant it
  was a tail exit instruction.
- None of the tests caught the regression either due to non-existent
  tests, or the tests being disabled/removed for continuous breakage.

This change re-introduces some of the basic tests and verifies that
we're back to a state that allows the back-end to generate appropriate
XRay instrumented binaries for PPC in the presence of tail exits.

Reviewers: echristo, timshen

Subscribers: nemanjai, kbarton, llvm-commits

Differential Revision: https://reviews.llvm.org/D37570

llvm-svn: 312772

1 files changed, 26 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/xray-tail-call-hidden.ll b/llvm/test/CodeGen/PowerPC/xray-tail-call-hidden.ll
new file mode 100644
index 00000000000..3b1cd5f5870
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/xray-tail-call-hidden.ll
@@ -0,0 +1,26 @@
+; RUN: llc -filetype=asm -o - -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
+
+declare hidden i32 @callee() nounwind noinline uwtable "function-instrument"="xray-always"
+
+define i32 @caller() nounwind noinline uwtable "function-instrument"="xray-always" {
+; CHECK-LABEL: .Ltmp0:
+; CHECK:              b .Ltmp1
+; CHECK-NEXT:         nop
+; CHECK-NEXT:         std 0, -8(1)
+; CHECK-NEXT:         mflr 0
+; CHECK-NEXT:         bl __xray_FunctionEntry
+; CHECK-NEXT:         nop
+; CHECK-NEXT:         mtlr 0
+; CHECK-LABEL: .Ltmp1:
+  %retval = tail call i32 @callee()
+  ret i32 %retval
+; CHECK-LABEL: .Ltmp2:
+; CHECK:              b callee
+; CHECK-NEXT:         nop
+; CHECK-NEXT:         std 0, -8(1)
+; CHECK-NEXT:         mflr 0
+; CHECK-NEXT:         bl __xray_FunctionExit
+; CHECK-NEXT:         nop
+; CHECK-NEXT:         mtlr 0
+}
+