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[ObjC] Override TailCallKind when lowering objc intrinsics

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The tail-call-kind-ness is known by the ObjCARC analysis and can be
enforced while lowering the intrinsics to calls.

This allows us to get the requested tail calls at -O0 without trying to
preserve the attributes throughout passes that change code even at -O0
,like the Always Inliner, where the ObjCOpt pass doesn't run.

Differential Revision: https://reviews.llvm.org/D69980
This commit is contained in:
Francis Visoiu Mistrih 2019-11-06 17:09:55 -08:00
parent 2978e175d1
commit 2523ca13cf
2 changed files with 30 additions and 6 deletions
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26
lib/CodeGen/PreISelIntrinsicLowering.cpp
View File

@ -12,6 +12,7 @@
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/PreISelIntrinsicLowering.h"
#include "llvm/Analysis/ObjCARCInstKind.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/Intrinsics.h"
@ -56,6 +57,17 @@ static bool lowerLoadRelative(Function &F) {
return Changed;
}
// ObjCARC has knowledge about whether an obj-c runtime function needs to be
// always tail-called or never tail-called.
static CallInst::TailCallKind getOverridingTailCallKind(const Function &F) {
objcarc::ARCInstKind Kind = objcarc::GetFunctionClass(&F);
if (objcarc::IsAlwaysTail(Kind))
return CallInst::TCK_Tail;
else if (objcarc::IsNeverTail(Kind))
return CallInst::TCK_NoTail;
return CallInst::TCK_None;
}
static bool lowerObjCCall(Function &F, const char *NewFn,
bool setNonLazyBind = false) {
if (F.use_empty())
@ -75,6 +87,8 @@ static bool lowerObjCCall(Function &F, const char *NewFn,
}
}
CallInst::TailCallKind OverridingTCK = getOverridingTailCallKind(F);
for (auto I = F.use_begin(), E = F.use_end(); I != E;) {
auto *CI = cast<CallInst>(I->getUser());
assert(CI->getCalledFunction() && "Cannot lower an indirect call!");
@ -84,7 +98,17 @@ static bool lowerObjCCall(Function &F, const char *NewFn,
SmallVector<Value *, 8> Args(CI->arg_begin(), CI->arg_end());
CallInst *NewCI = Builder.CreateCall(FCache, Args);
NewCI->setName(CI->getName());
NewCI->setTailCallKind(CI->getTailCallKind());
// Try to set the most appropriate TailCallKind based on both the current
// attributes and the ones that we could get from ObjCARC's special
// knowledge of the runtime functions.
//
// std::max respects both requirements of notail and tail here:
// * notail on either the call or from ObjCARC becomes notail
// * tail on either side is stronger than none, but not notail
CallInst::TailCallKind TCK = CI->getTailCallKind();
NewCI->setTailCallKind(std::max(TCK, OverridingTCK));
if (!CI->use_empty())
CI->replaceAllUsesWith(NewCI);
CI->eraseFromParent();

10
test/Transforms/PreISelIntrinsicLowering/objc-arc.ll
View File

@ -7,7 +7,7 @@
define i8* @test_objc_autorelease(i8* %arg0) {
; CHECK-LABEL: test_objc_autorelease
; CHECK-NEXT: entry
; CHECK-NEXT: %0 = call i8* @objc_autorelease(i8* %arg0)
; CHECK-NEXT: %0 = notail call i8* @objc_autorelease(i8* %arg0)
; CHECK-NEXT: ret i8* %0
entry:
%0 = call i8* @llvm.objc.autorelease(i8* %arg0)
@ -37,7 +37,7 @@ entry:
define i8* @test_objc_autoreleaseReturnValue(i8* %arg0) {
; CHECK-LABEL: test_objc_autoreleaseReturnValue
; CHECK-NEXT: entry
; CHECK-NEXT: %0 = call i8* @objc_autoreleaseReturnValue(i8* %arg0)
; CHECK-NEXT: %0 = tail call i8* @objc_autoreleaseReturnValue(i8* %arg0)
; CHECK-NEXT: ret i8* %0
entry:
%0 = call i8* @llvm.objc.autoreleaseReturnValue(i8* %arg0)
@ -117,7 +117,7 @@ entry:
define i8* @test_objc_retain(i8* %arg0) {
; CHECK-LABEL: test_objc_retain
; CHECK-NEXT: entry
; CHECK-NEXT: %0 = call i8* @objc_retain(i8* %arg0)
; CHECK-NEXT: %0 = tail call i8* @objc_retain(i8* %arg0)
; CHECK-NEXT: ret i8* %0
entry:
%0 = call i8* @llvm.objc.retain(i8* %arg0)
@ -147,7 +147,7 @@ entry:
define i8* @test_objc_retainAutoreleasedReturnValue(i8* %arg0) {
; CHECK-LABEL: test_objc_retainAutoreleasedReturnValue
; CHECK-NEXT: entry
; CHECK-NEXT: %0 = call i8* @objc_retainAutoreleasedReturnValue(i8* %arg0)
; CHECK-NEXT: %0 = tail call i8* @objc_retainAutoreleasedReturnValue(i8* %arg0)
; CHECK-NEXT: ret i8* %0
entry:
%0 = call i8* @llvm.objc.retainAutoreleasedReturnValue(i8* %arg0)
@ -187,7 +187,7 @@ entry:
define i8* @test_objc_unsafeClaimAutoreleasedReturnValue(i8* %arg0) {
; CHECK-LABEL: test_objc_unsafeClaimAutoreleasedReturnValue
; CHECK-NEXT: entry
; CHECK-NEXT: %0 = call i8* @objc_unsafeClaimAutoreleasedReturnValue(i8* %arg0)
; CHECK-NEXT: %0 = tail call i8* @objc_unsafeClaimAutoreleasedReturnValue(i8* %arg0)
; CHECK-NEXT: ret i8* %0
entry:
%0 = call i8* @llvm.objc.unsafeClaimAutoreleasedReturnValue(i8* %arg0)