From 7c2192b277e6050f30a1582efe5217b1ee904b1b Mon Sep 17 00:00:00 2001
From: Jin Lin <jinl@uber.com>
Date: Wed, 3 Mar 2021 12:06:42 -0800
Subject: [PATCH] Add the use of register r for outlined function when register
 r is live in and defined later.

The compiler needs to mark register $x0 as live in for the following case.

    $x1 = ADDXri $sp, 16, 0
    BL @spam, csr_darwin_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit killed $x1, implicit-def $sp, implicit-def dead $x0

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D95267
---
 llvm/lib/CodeGen/MachineOutliner.cpp               |  2 +-
 .../AArch64/machine-outliner-side-effect-2.mir     | 51 ++++++++++++++++++++++
 2 files changed, 52 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/CodeGen/AArch64/machine-outliner-side-effect-2.mir

diff --git a/llvm/lib/CodeGen/MachineOutliner.cpp b/llvm/lib/CodeGen/MachineOutliner.cpp
index 3751d94..1d55bd0 100644
--- a/llvm/lib/CodeGen/MachineOutliner.cpp
+++ b/llvm/lib/CodeGen/MachineOutliner.cpp
@@ -806,7 +806,7 @@ bool MachineOutliner::outline(Module &M,
             if (MOP.isDef()) {
               // Introduce DefRegs set to skip the redundant register.
               DefRegs.insert(MOP.getReg());
-              if (UseRegs.count(MOP.getReg()))
+              if (!MOP.isDead() && UseRegs.count(MOP.getReg()))
                 // Since the regiester is modeled as defined,
                 // it is not necessary to be put in use register set.
                 UseRegs.erase(MOP.getReg());
diff --git a/llvm/test/CodeGen/AArch64/machine-outliner-side-effect-2.mir b/llvm/test/CodeGen/AArch64/machine-outliner-side-effect-2.mir
new file mode 100644
index 0000000..d95565b
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/machine-outliner-side-effect-2.mir
@@ -0,0 +1,51 @@
+# RUN: llc -mtriple=aarch64 -run-pass=machine-outliner -verify-machineinstrs %s -o - | FileCheck %s
+
+# The test checks whether the compiler updates the side effect of function @OUTLINED_FUNCTION_0 by adding the use of register x0.
+
+--- |
+  declare void @spam() local_unnamed_addr
+  define void @bax() optsize minsize noredzone { ret void }
+  define void @bay() optsize minsize noredzone { ret void }
+  define void @baz() optsize minsize noredzone { ret void }
+...
+---
+name:            bax
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $lr
+
+    $x1 = ADDXri $sp, 16, 0
+    BL @spam, csr_darwin_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit killed $x1, implicit-def $sp, implicit-def dead $x0
+
+    RET_ReallyLR
+
+...
+---
+name:            bay
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $lr
+
+    $x1 = ADDXri $sp, 16, 0
+    BL @spam, csr_darwin_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit killed $x1, implicit-def $sp, implicit-def dead $x0
+
+    RET_ReallyLR
+
+...
+---
+name:            baz
+tracksRegLiveness: true
+body:             |
+  bb.0:
+    liveins: $x0, $lr
+
+    $x1 = ADDXri $sp, 16, 0
+    BL @spam, csr_darwin_aarch64_aapcs, implicit-def dead $lr, implicit $sp, implicit $x0, implicit killed $x1, implicit-def $sp, implicit-def dead $x0
+
+    RET_ReallyLR
+
+...
+
+# CHECK: BL @OUTLINED_FUNCTION_0, {{.*}}, implicit $x0
-- 
2.7.4