[llvm] [MachineSink] Some more preserving of debug location when rematerialising an instruction to replace a COPY (PR #73155)

[Momchil Velikov via llvm-commits]

https://github.com/momchil-velikov created https://github.com/llvm/llvm-project/pull/73155

Somewhet similar to ef9bcace834e63f25bbbc5e8e2b615f89d85fb2f
([MachineSink][AArch64] Preserve debug location when rematerialising
an instruction to replace a COPY (#72685))
reuse the debug location of the COPY, iff the rematerialised instruction
did not have a location.

>From 09f5177393ce0634c0a673bd42d08c6aaed31617 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Wed, 22 Nov 2023 17:19:01 +0000
Subject: [PATCH 1/2] [MachineSink] Some more preserving of debug location when
 rematerialising an instruction to replace a COPY

Somewhet similar to ef9bcace834e63f25bbbc5e8e2b615f89d85fb2f
([MachineSink][AArch64] Preserve debug location when rematerialising
 an instruction to replace a COPY (#72685))
reuse the debug location of the COPY, iff the rematerialised instruction
did not have a location.
---
 llvm/lib/CodeGen/MachineSink.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/CodeGen/MachineSink.cpp b/llvm/lib/CodeGen/MachineSink.cpp
index 48f5a21406f08a8..83d775055dfd733 100644
--- a/llvm/lib/CodeGen/MachineSink.cpp
+++ b/llvm/lib/CodeGen/MachineSink.cpp
@@ -506,7 +506,7 @@ bool MachineSinking::PerformSinkAndFold(MachineInstr &MI,
     MRI->clearKillFlags(UsedRegB);
 
   for (auto &[SinkDst, MaybeAM] : SinkInto) {
-    [[maybe_unused]] MachineInstr *New = nullptr;
+    MachineInstr *New = nullptr;
     LLVM_DEBUG(dbgs() << "Sinking copy of"; MI.dump(); dbgs() << "into";
                SinkDst->dump());
     if (SinkDst->isCopy()) {
@@ -525,6 +525,8 @@ bool MachineSinking::PerformSinkAndFold(MachineInstr &MI,
       Register DstReg = SinkDst->getOperand(0).getReg();
       TII->reMaterialize(*SinkDst->getParent(), InsertPt, DstReg, 0, MI, *TRI);
       New = &*std::prev(InsertPt);
+      if (!New->getDebugLoc())
+        New->setDebugLoc(SinkDst->getDebugLoc());
     } else {
       // Fold instruction into the addressing mode of a memory instruction.
       New = TII->emitLdStWithAddr(*SinkDst, MaybeAM);

>From 46647c566cb515c618624b3b97daae0a6e52e3f0 Mon Sep 17 00:00:00 2001
From: Momchil Velikov <momchil.velikov at arm.com>
Date: Wed, 22 Nov 2023 17:45:24 +0000
Subject: [PATCH 2/2] Revert "Revert "[MachineSink][AArch64] Enable
 sink-and-fold by default (#72132)""

This reverts commit 4ac5b0da8d71b72dc999a462ecfb3695d0803e7c.
---
 llvm/lib/Target/AArch64/AArch64TargetMachine.cpp | 2 +-
 llvm/test/CodeGen/AArch64/sink-and-fold.ll       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
index d418a297218eb06..036719be06d83f1 100644
--- a/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
+++ b/llvm/lib/Target/AArch64/AArch64TargetMachine.cpp
@@ -200,7 +200,7 @@ static cl::opt<bool> EnableGISelLoadStoreOptPostLegal(
 static cl::opt<bool>
     EnableSinkFold("aarch64-enable-sink-fold",
                    cl::desc("Enable sinking and folding of instruction copies"),
-                   cl::init(false), cl::Hidden);
+                   cl::init(true), cl::Hidden);
 
 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeAArch64Target() {
   // Register the target.
diff --git a/llvm/test/CodeGen/AArch64/sink-and-fold.ll b/llvm/test/CodeGen/AArch64/sink-and-fold.ll
index 632fdb391053121..52007221e12a7b5 100644
--- a/llvm/test/CodeGen/AArch64/sink-and-fold.ll
+++ b/llvm/test/CodeGen/AArch64/sink-and-fold.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -aarch64-enable-sink-fold=true < %s | FileCheck %s
+; RUN: llc < %s | FileCheck %s
 target triple = "aarch64-linux"
 
 declare i32 @use(...)