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Remove readnone from invariant.group.barrier
Summary:
Readnone attribute would cause CSE of two barriers with
the same argument, which is invalid by example:
struct Base {
virtual int foo() { return 42; }
};
struct Derived1 : Base {
int foo() override { return 50; }
};
struct Derived2 : Base {
int foo() override { return 100; }
};
void foo() {
Base *x = new Base{};
new (x) Derived1{};
int a = std::launder(x)->foo();
new (x) Derived2{};
int b = std::launder(x)->foo();
}
Here 2 calls of std::launder will produce @llvm.invariant.group.barrier,
which would be merged into one call, causing devirtualization
to devirtualize second call into Derived1::foo() instead of
Derived2::foo()
Reviewers: chandlerc, dberlin, hfinkel
Subscribers: llvm-commits, rsmith, amharc
Differential Revision: https://reviews.llvm.org/D31531
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@300101 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Piotr Padlewski
parent
4f344492bb
commit
6f93f61542
@ -615,9 +615,16 @@ def int_invariant_end : Intrinsic<[],
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llvm_anyptr_ty],
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[IntrArgMemOnly, NoCapture<2>]>;
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// invariant.group.barrier can't be marked with 'readnone' (IntrNoMem),
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// because it would cause CSE of two barriers with the same argument.
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// Readonly and argmemonly says that barrier only reads its argument and
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// it can be CSE only if memory didn't change between 2 barriers call,
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// which is valid.
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// The argument also can't be marked with 'returned' attribute, because
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// it would remove barrier.
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def int_invariant_group_barrier : Intrinsic<[llvm_ptr_ty],
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[llvm_ptr_ty],
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[IntrNoMem]>;
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[IntrReadMem, IntrArgMemOnly]>;
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//===------------------------ Stackmap Intrinsics -------------------------===//
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//
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@ -16,6 +16,8 @@ define i32 @foo(i32* %a) {
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store i32 1, i32* @g, align 4
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%1 = bitcast i32* %a to i8*
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a32 = bitcast i8* %a8 to i32*
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@ -33,6 +35,8 @@ define i32 @skipBarrier(i32* %a) {
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store i32 0, i32* %a, align 4, !invariant.group !0
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%1 = bitcast i32* %a to i8*
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; CHECK: MemoryUse(1)
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; CHECK-NEXT: %a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a32 = bitcast i8* %a8 to i32*
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@ -50,6 +54,8 @@ define i32 @skipBarrier2(i32* %a) {
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%v = load i32, i32* %a, align 4, !invariant.group !0
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%1 = bitcast i32* %a to i8*
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; CHECK: MemoryUse(liveOnEntry)
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; CHECK-NEXT: %a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a32 = bitcast i8* %a8 to i32*
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@ -79,6 +85,8 @@ define i32 @handleInvariantGroups(i32* %a) {
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; CHECK-NEXT: store i32 1
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store i32 1, i32* @g, align 4
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%1 = bitcast i32* %a to i8*
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a8 = call i8* @llvm.invariant.group.barrier(i8* %1)
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%a32 = bitcast i8* %a8 to i32*
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@ -135,6 +143,9 @@ entry:
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; CHECK: 2 = MemoryDef(1)
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; CHECK-NEXT: call void @clobber
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call void @clobber8(i8* %p)
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %after = call i8* @llvm.invariant.group.barrier(i8* %p)
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%after = call i8* @llvm.invariant.group.barrier(i8* %p)
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br i1 undef, label %Loop.Body, label %Loop.End
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@ -179,6 +190,9 @@ entry:
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; CHECK: 2 = MemoryDef(1)
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; CHECK-NEXT: call void @clobber
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call void @clobber8(i8* %p)
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %after = call i8* @llvm.invariant.group.barrier(i8* %p)
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%after = call i8* @llvm.invariant.group.barrier(i8* %p)
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br i1 undef, label %Loop.Body, label %Loop.End
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@ -238,6 +252,8 @@ entry:
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; CHECK: 2 = MemoryDef(1)
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; CHECK-NEXT: call void @clobber
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call void @clobber8(i8* %p)
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; CHECK: MemoryUse(2)
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; CHECK-NEXT: %after = call i8* @llvm.invariant.group.barrier(i8* %p)
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%after = call i8* @llvm.invariant.group.barrier(i8* %p)
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br i1 undef, label %Loop.Pre, label %Loop.End
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62
test/Other/invariant.group.barrier.ll
Normal file
62
test/Other/invariant.group.barrier.ll
Normal file
@ -0,0 +1,62 @@
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; RUN: opt -S -early-cse < %s | FileCheck %s
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; RUN: opt -S -gvn < %s | FileCheck %s
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; RUN: opt -S -newgvn < %s | FileCheck %s
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; RUN: opt -S -O3 < %s | FileCheck %s
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; These tests checks if passes with CSE functionality can do CSE on
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; invariant.group.barrier, that is prohibited if there is a memory clobber
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; between barriers call.
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; CHECK-LABEL: define i8 @optimizable()
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define i8 @optimizable() {
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entry:
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%ptr = alloca i8
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store i8 42, i8* %ptr, !invariant.group !0
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; CHECK: call i8* @llvm.invariant.group.barrier
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%ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
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; CHECK-NOT: call i8* @llvm.invariant.group.barrier
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%ptr3 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
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; CHECK: call void @clobber(i8* {{.*}}%ptr)
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call void @clobber(i8* %ptr)
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; CHECK: call void @use(i8* {{.*}}%ptr2)
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call void @use(i8* %ptr2)
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; CHECK: call void @use(i8* {{.*}}%ptr2)
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call void @use(i8* %ptr3)
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; CHECK: load i8, i8* %ptr2, {{.*}}!invariant.group
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%v = load i8, i8* %ptr3, !invariant.group !0
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ret i8 %v
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}
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; CHECK-LABEL: define i8 @unoptimizable()
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define i8 @unoptimizable() {
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entry:
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%ptr = alloca i8
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store i8 42, i8* %ptr, !invariant.group !0
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; CHECK: call i8* @llvm.invariant.group.barrier
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%ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
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call void @clobber(i8* %ptr)
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; CHECK: call i8* @llvm.invariant.group.barrier
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%ptr3 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
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; CHECK: call void @clobber(i8* {{.*}}%ptr)
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call void @clobber(i8* %ptr)
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; CHECK: call void @use(i8* {{.*}}%ptr2)
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call void @use(i8* %ptr2)
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; CHECK: call void @use(i8* {{.*}}%ptr3)
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call void @use(i8* %ptr3)
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; CHECK: load i8, i8* %ptr3, {{.*}}!invariant.group
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%v = load i8, i8* %ptr3, !invariant.group !0
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ret i8 %v
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}
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declare void @use(i8* readonly)
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declare void @clobber(i8*)
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; CHECK: Function Attrs: argmemonly nounwind readonly
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; CHECK-NEXT: declare i8* @llvm.invariant.group.barrier(i8*)
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declare i8* @llvm.invariant.group.barrier(i8*)
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!0 = !{}
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