[PATCH] D78335: [GIsel][LegalizerHelper] Account for debug insts when creating mem libcalls

[Vedant Kumar via Phabricator via llvm-commits]

vsk created this revision.
vsk added reviewers: dsanders, aemerson.
Herald added a subscriber: hiraditya.
Herald added a project: LLVM.

While lowering memory intrinsics, GIsel attempts to form a tail call to
a library routine.

There might be a DBG_LABEL or something after the intrinsic call,
though: in that case, GIsel should still be able to form the tail call,
and should also delete the debug insts after the tail call as the
transform makes them invalid.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78335

Files:
  llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
  llvm/test/CodeGen/AArch64/GlobalISel/legalize-memcpy-et-al.mir


Index: llvm/test/CodeGen/AArch64/GlobalISel/legalize-memcpy-et-al.mir
===================================================================
--- llvm/test/CodeGen/AArch64/GlobalISel/legalize-memcpy-et-al.mir
+++ llvm/test/CodeGen/AArch64/GlobalISel/legalize-memcpy-et-al.mir
@@ -1,5 +1,6 @@
 # NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
 # RUN: llc -march=aarch64 -run-pass=legalizer -verify-machineinstrs %s -o - | FileCheck %s
+# RUN: llc -debugify-and-strip-all-safe -march=aarch64 -run-pass=legalizer -verify-machineinstrs %s -o - | FileCheck %s
 ---
 name:            test_memcpy
 tracksRegLiveness: true
Index: llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
===================================================================
--- llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -462,7 +462,8 @@
 /// True if an instruction is in tail position in its caller. Intended for
 /// legalizing libcalls as tail calls when possible.
 static bool isLibCallInTailPosition(MachineInstr &MI) {
-  const Function &F = MI.getParent()->getParent()->getFunction();
+  MachineBasicBlock &MBB = *MI.getParent();
+  const Function &F = MBB.getParent()->getFunction();
 
   // Conservatively require the attributes of the call to match those of
   // the return. Ignore NoAlias and NonNull because they don't affect the
@@ -481,8 +482,8 @@
 
   // Only tail call if the following instruction is a standard return.
   auto &TII = *MI.getMF()->getSubtarget().getInstrInfo();
-  MachineInstr *Next = MI.getNextNode();
-  if (!Next || TII.isTailCall(*Next) || !Next->isReturn())
+  auto Next = next_nodbg(MI.getIterator(), MBB.instr_end());
+  if (Next == MBB.instr_end() || TII.isTailCall(*Next) || !Next->isReturn())
     return false;
 
   return true;
@@ -584,14 +585,16 @@
 
   if (Info.LoweredTailCall) {
     assert(Info.IsTailCall && "Lowered tail call when it wasn't a tail call?");
-    // We must have a return following the call to get past
+    // We must have a return following the call (or debug insts) to get past
     // isLibCallInTailPosition.
-    assert(MI.getNextNode() && MI.getNextNode()->isReturn() &&
-           "Expected instr following MI to be a return?");
-
-    // We lowered a tail call, so the call is now the return from the block.
-    // Delete the old return.
-    MI.getNextNode()->eraseFromParent();
+    do {
+      MachineInstr *Next = MI.getNextNode();
+      assert(Next && (Next->isReturn() || Next->isDebugInstr()) &&
+             "Expected instr following MI to be return or debug inst?");
+      // We lowered a tail call, so the call is now the return from the block.
+      // Delete the old return.
+      Next->eraseFromParent();
+    } while (MI.getNextNode());
   }
 
   return LegalizerHelper::Legalized;


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D78335.258189.patch
Type: text/x-patch
Size: 2830 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20200416/cabe1eaa/attachment.bin>