1 files changed, 87 insertions, 0 deletions
diff --git a/0015-Backport-ARM-Check-all-terms-in-emitPopInst-when-clearing-Res.patch b/0015-Backport-ARM-Check-all-terms-in-emitPopInst-when-clearing-Res.patch
new file mode 100644
index 0000000..4528f50
--- /dev/null
+++ b/0015-Backport-ARM-Check-all-terms-in-emitPopInst-when-clearing-Res.patch
@@ -0,0 +1,87 @@
+From 4aec2da60ce3f639e31d81406c09d5c88b3b8f53 Mon Sep 17 00:00:00 2001
+From: Florian Hahn <flo@fhahn.com>
+Date: Wed, 20 Dec 2023 16:56:15 +0100
+Subject: [PATCH 2/3] [ARM] Check all terms in emitPopInst when clearing
+ Restored for LR. (#75527)
+
+emitPopInst checks a single function exit MBB. If other paths also exit
+the function and any of there terminators uses LR implicitly, it is not
+save to clear the Restored bit.
+
+Check all terminators for the function before clearing Restored.
+
+This fixes a mis-compile in outlined-fn-may-clobber-lr-in-caller.ll
+where the machine-outliner previously introduced BLs that clobbered LR
+which in turn is used by the tail call return.
+
+Alternative to #73553
+---
+ llvm/lib/Target/ARM/ARMFrameLowering.cpp | 30 +++++++++++++++++++++---
+ llvm/lib/Target/ARM/ARMFrameLowering.h   |  3 +++
+ 2 files changed, 30 insertions(+), 3 deletions(-)
+
+diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.cpp b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+index 4496d4928ebe..650f4650eef0 100644
+--- a/llvm/lib/Target/ARM/ARMFrameLowering.cpp
++++ b/llvm/lib/Target/ARM/ARMFrameLowering.cpp
+@@ -1645,9 +1645,6 @@ void ARMFrameLowering::emitPopInst(MachineBasicBlock &MBB,
+         // Fold the return instruction into the LDM.
+         DeleteRet = true;
+         LdmOpc = AFI->isThumbFunction() ? ARM::t2LDMIA_RET : ARM::LDMIA_RET;
+-        // We 'restore' LR into PC so it is not live out of the return block:
+-        // Clear Restored bit.
+-        Info.setRestored(false);
+       }
+ 
+       // If NoGap is true, pop consecutive registers and then leave the rest
+@@ -2769,6 +2766,33 @@ void ARMFrameLowering::determineCalleeSaves(MachineFunction &MF,
+   AFI->setLRIsSpilled(SavedRegs.test(ARM::LR));
+ }
+ 
++void ARMFrameLowering::processFunctionBeforeFrameFinalized(
++    MachineFunction &MF, RegScavenger *RS) const {
++  TargetFrameLowering::processFunctionBeforeFrameFinalized(MF, RS);
++
++  MachineFrameInfo &MFI = MF.getFrameInfo();
++  if (!MFI.isCalleeSavedInfoValid())
++    return;
++
++  // Check if all terminators do not implicitly use LR. Then we can 'restore' LR
++  // into PC so it is not live out of the return block: Clear the Restored bit
++  // in that case.
++  for (CalleeSavedInfo &Info : MFI.getCalleeSavedInfo()) {
++    if (Info.getReg() != ARM::LR)
++      continue;
++    if (all_of(MF, [](const MachineBasicBlock &MBB) {
++          return all_of(MBB.terminators(), [](const MachineInstr &Term) {
++            return !Term.isReturn() || Term.getOpcode() == ARM::LDMIA_RET ||
++                   Term.getOpcode() == ARM::t2LDMIA_RET ||
++                   Term.getOpcode() == ARM::tPOP_RET;
++          });
++        })) {
++      Info.setRestored(false);
++      break;
++    }
++  }
++}
++
+ void ARMFrameLowering::getCalleeSaves(const MachineFunction &MF,
+                                       BitVector &SavedRegs) const {
+   TargetFrameLowering::getCalleeSaves(MF, SavedRegs);
+diff --git a/llvm/lib/Target/ARM/ARMFrameLowering.h b/llvm/lib/Target/ARM/ARMFrameLowering.h
+index 16f2ce6bea6f..8d2b8beb9a58 100644
+--- a/llvm/lib/Target/ARM/ARMFrameLowering.h
++++ b/llvm/lib/Target/ARM/ARMFrameLowering.h
+@@ -59,6 +59,9 @@ public:
+   void determineCalleeSaves(MachineFunction &MF, BitVector &SavedRegs,
+                             RegScavenger *RS) const override;
+ 
++  void processFunctionBeforeFrameFinalized(
++      MachineFunction &MF, RegScavenger *RS = nullptr) const override;
++
+   void adjustForSegmentedStacks(MachineFunction &MF,
+                                 MachineBasicBlock &MBB) const override;
+ 
+-- 
+2.33.0
+