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, 40 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/ARM/disable-tail-calls.ll b/llvm/test/CodeGen/ARM/disable-tail-calls.ll
new file mode 100644
index 00000000000..18aa4723fd3
--- /dev/null
+++ b/llvm/test/CodeGen/ARM/disable-tail-calls.ll
@@ -0,0 +1,40 @@
+; RUN: llc < %s -march arm | FileCheck %s --check-prefix=NO-OPTION
+; RUN: llc < %s -march arm -disable-tail-calls | FileCheck %s --check-prefix=DISABLE-TRUE
+; RUN: llc < %s -march arm -disable-tail-calls=false | FileCheck %s --check-prefix=DISABLE-FALSE
+
+; Check that command line option "-disable-tail-calls" overrides function
+; attribute "disable-tail-calls".
+
+; NO-OPTION-LABEL: {{\_?}}func_attr
+; NO-OPTION: bl {{\_?}}callee
+
+; DISABLE-FALSE-LABEL: {{\_?}}func_attr
+; DISABLE-FALSE: b {{\_?}}callee
+
+; DISABLE-TRUE-LABEL: {{\_?}}func_attr
+; DISABLE-TRUE: bl {{\_?}}callee
+
+define i32 @func_attr(i32 %a) #0 {
+entry:
+  %call = tail call i32 @callee(i32 %a)
+  ret i32 %call
+}
+
+; NO-OPTION-LABEL: {{\_?}}func_noattr
+; NO-OPTION: b {{\_?}}callee
+
+; DISABLE-FALSE-LABEL: {{\_?}}func_noattr
+; DISABLE-FALSE: b {{\_?}}callee
+
+; DISABLE-TRUE-LABEL: {{\_?}}func_noattr
+; DISABLE-TRUE: bl {{\_?}}callee
+
+define i32 @func_noattr(i32 %a) {
+entry:
+  %call = tail call i32 @callee(i32 %a)
+  ret i32 %call
+}
+
+declare i32 @callee(i32)
+
+attributes #0 = { "disable-tail-calls"="true" }