Remove DisableTailCalls from TargetOptions and the code in resetTargetOptions

that was resetting it.

Remove the uses of DisableTailCalls in subclasses of TargetLowering and use
the value of function attribute "disable-tail-calls" instead. Also,
unconditionally add pass TailCallElim to the pipeline and check the function
attribute at the start of runOnFunction to disable the pass on a per-function
basis. 
 
This is part of the work to remove TargetMachine::resetTargetOptions, and since
DisableTailCalls was the last non-fast-math option that was being reset in that
function, we should be able to remove the function entirely after the work to
propagate IR-level fast-math flags to DAG nodes is completed.

Out-of-tree users should remove the uses of DisableTailCalls and make changes
to attach attribute "disable-tail-calls"="true" or "false" to the functions in
the IR.

rdar://problem/13752163

Differential Revision: http://reviews.llvm.org/D10099

llvm-svn: 239427

1 files changed, 5 insertions, 2 deletions

diff --git a/llvm/lib/Target/ARM/ARMISelLowering.cpp b/llvm/lib/Target/ARM/ARMISelLowering.cpp
index 47c8400a668..2cfbc39a05b 100644
--- a/llvm/lib/Target/ARM/ARMISelLowering.cpp
+++ b/llvm/lib/Target/ARM/ARMISelLowering.cpp
@@ -1483,9 +1483,10 @@ ARMTargetLowering::LowerCall(TargetLowering::CallLoweringInfo &CLI,
   bool isStructRet    = (Outs.empty()) ? false : Outs[0].Flags.isSRet();
   bool isThisReturn   = false;
   bool isSibCall      = false;
+  auto Attr = MF.getFunction()->getFnAttribute("disable-tail-calls");
 
   // Disable tail calls if they're not supported.
-  if (!Subtarget->supportsTailCall() || MF.getTarget().Options.DisableTailCalls)
+  if (!Subtarget->supportsTailCall() || Attr.getValueAsString() == "true")
     isTailCall = false;
 
   if (isTailCall) {
@@ -2375,7 +2376,9 @@ bool ARMTargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
   if (!Subtarget->supportsTailCall())
     return false;
 
-  if (!CI->isTailCall() || getTargetMachine().Options.DisableTailCalls)
+  auto Attr =
+      CI->getParent()->getParent()->getFnAttribute("disable-tail-calls");
+  if (!CI->isTailCall() || Attr.getValueAsString() == "true")
     return false;
 
   return !Subtarget->isThumb1Only();