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Set the "tail" flag on pattern-matched objc_storeStrong calls. 

rdar://10531041.

llvm-svn: 148490
This commit is contained in:
Dan Gohman 2012-01-19 19:14:36 +00:00
parent f83dcfd052
commit 8ee108bf98
3 changed files with 34 additions and 2 deletions
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32
llvm/lib/Transforms/Scalar/ObjCARC.cpp
View File

@ -3600,6 +3600,11 @@ namespace {
/// RetainRV calls to make the optimization work on targets which need it.
const MDString *RetainRVMarker;
/// StoreStrongCalls - The set of inserted objc_storeStrong calls. If
/// at the end of walking the function we have found no alloca
/// instructions, these calls can be marked "tail".
DenseSet<CallInst *> StoreStrongCalls;
Constant *getStoreStrongCallee(Module *M);
Constant *getRetainAutoreleaseCallee(Module *M);
Constant *getRetainAutoreleaseRVCallee(Module *M);
@ -3803,6 +3808,11 @@ void ObjCARCContract::ContractRelease(Instruction *Release,
StoreStrong->setDoesNotThrow();
StoreStrong->setDebugLoc(Store->getDebugLoc());
// We can't set the tail flag yet, because we haven't yet determined
// whether there are any escaping allocas. Remember this call, so that
// we can set the tail flag once we know it's safe.
StoreStrongCalls.insert(StoreStrong);
if (&*Iter == Store) ++Iter;
Store->eraseFromParent();
Release->eraseFromParent();
@ -3849,6 +3859,13 @@ bool ObjCARCContract::runOnFunction(Function &F) {
PA.setAA(&getAnalysis<AliasAnalysis>());
// Track whether it's ok to mark objc_storeStrong calls with the "tail"
// keyword. Be conservative if the function has variadic arguments.
// It seems that functions which "return twice" are also unsafe for the
// "tail" argument, because they are setjmp, which could need to
// return to an earlier stack state.
bool TailOkForStoreStrongs = !F.isVarArg() && !F.callsFunctionThatReturnsTwice();
// For ObjC library calls which return their argument, replace uses of the
// argument with uses of the call return value, if it dominates the use. This
// reduces register pressure.
@ -3905,6 +3922,13 @@ bool ObjCARCContract::runOnFunction(Function &F) {
case IC_Release:
ContractRelease(Inst, I);
continue;
case IC_User:
// Be conservative if the function has any alloca instructions.
// Technically we only care about escaping alloca instructions,
// but this is sufficient to handle some interesting cases.
if (isa<AllocaInst>(Inst))
TailOkForStoreStrongs = false;
continue;
default:
continue;
}
@ -3969,5 +3993,13 @@ bool ObjCARCContract::runOnFunction(Function &F) {
}
}
// If this function has no escaping allocas or suspicious vararg usage,
// objc_storeStrong calls can be marked with the "tail" keyword.
if (TailOkForStoreStrongs)
for (DenseSet<CallInst *>::iterator I = StoreStrongCalls.begin(),
E = StoreStrongCalls.end(); I != E; ++I)
(*I)->setTailCall();
StoreStrongCalls.clear();
return Changed;
}

2
llvm/test/Transforms/ObjCARC/contract-storestrong-ivar.ll
View File

@ -1,6 +1,6 @@
; RUN: opt -objc-arc-contract -S < %s | FileCheck %s
; CHECK: call void @objc_storeStrong(i8**
; CHECK: tail call void @objc_storeStrong(i8**
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin11.0.0"

2
llvm/test/Transforms/ObjCARC/contract-storestrong.ll
View File

@ -9,7 +9,7 @@ declare void @objc_release(i8*)
; CHECK: define void @test0(
; CHECK: entry:
; CHECK-NEXT: call void @objc_storeStrong(i8** @x, i8* %p) nounwind
; CHECK-NEXT: tail call void @objc_storeStrong(i8** @x, i8* %p) nounwind
; CHECK-NEXT: ret void
define void @test0(i8* %p) {
entry: