[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, 7 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/XRayInstrumentation.cpp b/llvm/lib/CodeGen/XRayInstrumentation.cpp
index 0b4c6e55166..e6b65825f5b 100644
--- a/llvm/lib/CodeGen/XRayInstrumentation.cpp
+++ b/llvm/lib/CodeGen/XRayInstrumentation.cpp
@@ -14,8 +14,8 @@
 //
 //===---------------------------------------------------------------------===//
 
-#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineDominators.h"
@@ -109,22 +109,13 @@ void XRayInstrumentation::replaceRetWithPatchableRet(
 
 void XRayInstrumentation::prependRetWithPatchableExit(
     MachineFunction &MF, const TargetInstrInfo *TII) {
-  for (auto &MBB : MF) {
-    for (auto &T : MBB.terminators()) {
-      unsigned Opc = 0;
+  for (auto &MBB : MF)
+    for (auto &T : MBB.terminators())
       if (T.isReturn()) {
-        Opc = TargetOpcode::PATCHABLE_FUNCTION_EXIT;
-      }
-      if (TII->isTailCall(T)) {
-        Opc = TargetOpcode::PATCHABLE_TAIL_CALL;
-      }
-      if (Opc != 0) {
-        // Prepend the return instruction with PATCHABLE_FUNCTION_EXIT or
-        //   PATCHABLE_TAIL_CALL .
-        BuildMI(MBB, T, T.getDebugLoc(), TII->get(Opc));
+        // Prepend the return instruction with PATCHABLE_FUNCTION_EXIT.
+        BuildMI(MBB, T, T.getDebugLoc(),
+                TII->get(TargetOpcode::PATCHABLE_FUNCTION_EXIT));
       }
-    }
-  }
 }
 
 bool XRayInstrumentation::runOnMachineFunction(MachineFunction &MF) {
@@ -143,7 +134,7 @@ bool XRayInstrumentation::runOnMachineFunction(MachineFunction &MF) {
 
     // Count the number of MachineInstr`s in MachineFunction
     int64_t MICount = 0;
-    for (const auto& MBB : MF)
+    for (const auto &MBB : MF)
       MICount += MBB.size();
 
     // Check if we have a loop.