From 003bcad9a8b21e15e3786a52b1dafa844075ab84 Mon Sep 17 00:00:00 2001
From: Jon Roelofs <jonathan_roelofs@apple.com>
Date: Fri, 15 Sep 2023 10:04:56 -0700
Subject: [ARM] Always lower direct calls as direct when the outliner is
 enabled (#66434)

The indirect lowering hinders the outliner's ability to see that
sequences are in fact common, since the sequence similarity is rendered
opaque by the register callee. The size savings from making them
indirect seems to be dwarfed by the outliner's savings from
de-duplication.

rdar://115178034
rdar://115459865
---
 llvm/lib/CodeGen/TargetPassConfig.cpp     |  3 +++
 llvm/lib/Target/ARM/ARMISelLowering.cpp   |  8 ++++++++
 llvm/test/CodeGen/ARM/minsize-call-cse.ll | 13 +++++++++----
 llvm/test/CodeGen/ARM/pr42062.ll          |  2 +-
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/CodeGen/TargetPassConfig.cpp b/llvm/lib/CodeGen/TargetPassConfig.cpp
index e6ecbc9..94a3264 100644
--- a/llvm/lib/CodeGen/TargetPassConfig.cpp
+++ b/llvm/lib/CodeGen/TargetPassConfig.cpp
@@ -1241,6 +1241,9 @@ void TargetPassConfig::addMachinePasses() {
   addPass(&LiveDebugValuesID);
   addPass(&MachineSanitizerBinaryMetadataID);
 
+  if (EnableMachineOutliner == RunOutliner::NeverOutline)
+    TM->Options.EnableMachineOutliner = false;
+
   if (TM->Options.EnableMachineOutliner &&
       getOptLevel() != CodeGenOptLevel::None &&
       EnableMachineOutliner != RunOutliner::NeverOutline) {
diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index d9ae95d..21489a6 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -2395,6 +2395,14 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
                          return isa<Instruction>(U) &&
                                 cast<Instruction>(U)->getParent() == BB;
                        }) > 2;
+      // The indirect call lowering hinders the MachineOutliner's ability to
+      // recognize common sequences. The resulting indirect calls all have the
+      // same target, but the outliner can't tell this a priori, since the
+      // branch target is turned into a register operand, and those can't (yet?)
+      // be assumed to have the same value at runtime.
+      const TargetOptions &Options = DAG.getTarget().Options;
+      if (Options.EnableMachineOutliner)
+        PreferIndirect = false;
     }
   }
   if (isTailCall) {
diff --git a/llvm/test/CodeGen/ARM/minsize-call-cse.ll b/llvm/test/CodeGen/ARM/minsize-call-cse.ll
index 072b76f..3a72dd2 100644
--- a/llvm/test/CodeGen/ARM/minsize-call-cse.ll
+++ b/llvm/test/CodeGen/ARM/minsize-call-cse.ll
@@ -1,12 +1,17 @@
-; RUN: llc < %s | FileCheck %s
+; RUN: llc < %s | FileCheck %s --check-prefixes=OUTLINER,CHECK
+; RUN: llc -enable-machine-outliner=always < %s | FileCheck %s --check-prefixes=OUTLINER,CHECK
+; RUN: llc -enable-machine-outliner=never < %s  | FileCheck %s --check-prefixes=INDIRECT,CHECK
 
 target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "thumbv7m-arm-none-eabi"
 
 ; CHECK-LABEL: f:
-; CHECK: blx r
-; CHECK: blx r
-; CHECK: blx r
+; OUTLINER: bl g
+; OUTLINER: bl g
+; OUTLINER: bl g
+; INDIRECT: blx r
+; INDIRECT: blx r
+; INDIRECT: blx r
 define void @f() minsize optsize {
 entry:
   call void @g(i32 45, i32 66)
diff --git a/llvm/test/CodeGen/ARM/pr42062.ll b/llvm/test/CodeGen/ARM/pr42062.ll
index 8396f93..ba7e436a 100644
--- a/llvm/test/CodeGen/ARM/pr42062.ll
+++ b/llvm/test/CodeGen/ARM/pr42062.ll
@@ -1,5 +1,5 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc -o - %s 2>&1 | FileCheck %s --implicit-check-not=error
+; RUN: llc -o - %s -enable-machine-outliner=never 2>&1 | FileCheck %s --implicit-check-not=error
 target triple = "thumbv8m.base-arm-none-eabi"
 @foo = external global i8
 declare i32 @bar(ptr nocapture, i32, i32, ptr nocapture)
-- 
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