From 90d0ed297fabb373a29222b18f127dc853557bc8 Mon Sep 17 00:00:00 2001
From: Saleem Abdulrasool <compnerd@compnerd.org>
Date: Tue, 11 Mar 2014 15:09:54 +0000
Subject: ARM: honour -f{no-,}optimize-sibling-calls

Use the options in the ARMISelLowering to control whether tail calls are
optimised or not.  Previously, this option was entirely ignored on the ARM
target and only honoured on x86.

This option is mostly useful in profiling scenarios.  The default remains that
tail call optimisations will be applied.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203577 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/ARM/ARMISelLowering.cpp |  6 ++++--
 test/CodeGen/ARM/tail-call.ll      | 21 +++++++++++++++++++++
 2 files changed, 25 insertions(+), 2 deletions(-)
 create mode 100644 test/CodeGen/ARM/tail-call.ll

diff --git a/lib/Target/ARM/ARMISelLowering.cpp b/lib/Target/ARM/ARMISelLowering.cpp
index 8f646deb26..3d026be513 100644
--- a/lib/Target/ARM/ARMISelLowering.cpp
+++ b/lib/Target/ARM/ARMISelLowering.cpp
@@ -1439,9 +1439,11 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   bool isStructRet    = (Outs.empty()) ? false : Outs[0].Flags.isSRet();
   bool isThisReturn   = false;
   bool isSibCall      = false;
+
   // Disable tail calls if they're not supported.
-  if (!Subtarget->supportsTailCall())
+  if (!Subtarget->supportsTailCall() || MF.getTarget().Options.DisableTailCalls)
     isTailCall = false;
+
   if (isTailCall) {
     // Check if it's really possible to do a tail call.
     isTailCall = IsEligibleForTailCallOptimization(Callee, CallConv,
@@ -2273,7 +2275,7 @@ bool ARMTargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
   if (!Subtarget->supportsTailCall())
     return false;
 
-  if (!CI->isTailCall())
+  if (!CI->isTailCall() || getTargetMachine().Options.DisableTailCalls)
     return false;
 
   return !Subtarget->isThumb1Only();
diff --git a/test/CodeGen/ARM/tail-call.ll b/test/CodeGen/ARM/tail-call.ll
new file mode 100644
index 0000000000..270b41d956
--- /dev/null
+++ b/test/CodeGen/ARM/tail-call.ll
@@ -0,0 +1,21 @@
+; RUN: llc -mtriple armv7 -O0 -o - < %s | FileCheck %s -check-prefix CHECK-TAIL
+; RUN: llc -mtriple armv7 -O0 -disable-tail-calls -o - < %s \
+; RUN:   | FileCheck %s -check-prefix CHECK-NO-TAIL
+
+declare i32 @callee(i32 %i)
+
+define i32 @caller(i32 %i) {
+entry:
+  %r = tail call i32 @callee(i32 %i)
+  ret i32 %r
+}
+
+; CHECK-LABEL: caller
+; CHECK-TAIL: b callee
+
+; CHECK-LABEL: caller
+; CHECK-NO-TAIL: push {lr}
+; CHECK-NO-TAIL: bl callee
+; CHECK-NO-TAIL: pop {lr}
+; CHECK-NO-TAIL: bx lr
+
-- 
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