maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity
llvm-project/llvm/test/Transforms/NewGVN/invariant.group.ll

455 lines
14 KiB
LLVM
Raw Normal View History

[GVN] Initial check-in of a new global value numbering algorithm. The code have been developed by Daniel Berlin over the years, and the new implementation goal is that of addressing shortcomings of the current GVN infrastructure, i.e. long compile time for large testcases, lack of phi predication, no load/store value numbering etc... The current code just implements the "core" GVN algorithm, although other pieces (load coercion, phi handling, predicate system) are already implemented in a branch out of tree. Once the core is stable, we'll start adding pieces on top of the base framework. The test currently living in test/Transform/NewGVN are a copy of the ones in GVN, with proper `XFAIL` (missing features in NewGVN). A flag will be added in a future commit to enable NewGVN, so that interested parties can exercise this code easily. Differential Revision: https://reviews.llvm.org/D26224 llvm-svn: 290346
2016-12-23 00:03:48 +08:00
; XFAIL: *
; RUN: opt < %s -newgvn -S | FileCheck %s
%struct.A = type { i32 (...)** }
@_ZTV1A = available_externally unnamed_addr constant [3 x i8*] [i8* null, i8* bitcast (i8** @_ZTI1A to i8*), i8* bitcast (void (%struct.A*)* @_ZN1A3fooEv to i8*)], align 8
@_ZTI1A = external constant i8*
@unknownPtr = external global i8
; CHECK-LABEL: define i8 @simple() {
define i8 @simple() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0
%b = load i8, i8* %ptr, !invariant.group !0
%c = load i8, i8* %ptr, !invariant.group !0
; CHECK: ret i8 42
ret i8 %a
}
; CHECK-LABEL: define i8 @optimizable1() {
define i8 @optimizable1() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
%ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr2); call to use %ptr2
; CHECK: ret i8 42
ret i8 %a
}
; CHECK-LABEL: define i8 @optimizable2() {
define i8 @optimizable2() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr)
store i8 13, i8* %ptr ; can't use this store with invariant.group
%a = load i8, i8* %ptr
call void @bar(i8 %a) ; call to use %a
call void @foo(i8* %ptr)
%b = load i8, i8* %ptr, !invariant.group !0
; CHECK: ret i8 42
ret i8 %b
}
; CHECK-LABEL: define i8 @unoptimizable1() {
define i8 @unoptimizable1() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0
; CHECK: ret i8 %a
ret i8 %a
}
; CHECK-LABEL: define void @indirectLoads() {
define void @indirectLoads() {
entry:
%a = alloca %struct.A*, align 8
%0 = bitcast %struct.A** %a to i8*
%call = call i8* @getPointer(i8* null)
%1 = bitcast i8* %call to %struct.A*
call void @_ZN1AC1Ev(%struct.A* %1)
%2 = bitcast %struct.A* %1 to i8***
; CHECK: %vtable = load {{.*}} !invariant.group
%vtable = load i8**, i8*** %2, align 8, !invariant.group !2
%cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
call void @llvm.assume(i1 %cmp.vtables)
store %struct.A* %1, %struct.A** %a, align 8
%3 = load %struct.A*, %struct.A** %a, align 8
%4 = bitcast %struct.A* %3 to void (%struct.A*)***
; CHECK: call void @_ZN1A3fooEv(
%vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
%vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
%5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
call void %5(%struct.A* %3)
%6 = load %struct.A*, %struct.A** %a, align 8
%7 = bitcast %struct.A* %6 to void (%struct.A*)***
; CHECK: call void @_ZN1A3fooEv(
%vtable2 = load void (%struct.A*)**, void (%struct.A*)*** %7, align 8, !invariant.group !2
%vfn3 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable2, i64 0
%8 = load void (%struct.A*)*, void (%struct.A*)** %vfn3, align 8
call void %8(%struct.A* %6)
%9 = load %struct.A*, %struct.A** %a, align 8
%10 = bitcast %struct.A* %9 to void (%struct.A*)***
%vtable4 = load void (%struct.A*)**, void (%struct.A*)*** %10, align 8, !invariant.group !2
%vfn5 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable4, i64 0
%11 = load void (%struct.A*)*, void (%struct.A*)** %vfn5, align 8
; CHECK: call void @_ZN1A3fooEv(
call void %11(%struct.A* %9)
%vtable5 = load i8**, i8*** %2, align 8, !invariant.group !2
%vfn6 = getelementptr inbounds i8*, i8** %vtable5, i64 0
%12 = bitcast i8** %vfn6 to void (%struct.A*)**
%13 = load void (%struct.A*)*, void (%struct.A*)** %12, align 8
; CHECK: call void @_ZN1A3fooEv(
call void %13(%struct.A* %9)
ret void
}
; CHECK-LABEL: define void @combiningBitCastWithLoad() {
define void @combiningBitCastWithLoad() {
entry:
%a = alloca %struct.A*, align 8
%0 = bitcast %struct.A** %a to i8*
%call = call i8* @getPointer(i8* null)
%1 = bitcast i8* %call to %struct.A*
call void @_ZN1AC1Ev(%struct.A* %1)
%2 = bitcast %struct.A* %1 to i8***
; CHECK: %vtable = load {{.*}} !invariant.group
%vtable = load i8**, i8*** %2, align 8, !invariant.group !2
%cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
store %struct.A* %1, %struct.A** %a, align 8
; CHECK-NOT: !invariant.group
%3 = load %struct.A*, %struct.A** %a, align 8
%4 = bitcast %struct.A* %3 to void (%struct.A*)***
%vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
%vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
%5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
call void %5(%struct.A* %3)
ret void
}
; CHECK-LABEL:define void @loadCombine() {
define void @loadCombine() {
enter:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
; CHECK: %[[A:.*]] = load i8, i8* %ptr, !invariant.group
%a = load i8, i8* %ptr, !invariant.group !0
; CHECK-NOT: load
%b = load i8, i8* %ptr, !invariant.group !1
; CHECK: call void @bar(i8 %[[A]])
call void @bar(i8 %a)
; CHECK: call void @bar(i8 %[[A]])
call void @bar(i8 %b)
ret void
}
; CHECK-LABEL: define void @loadCombine1() {
define void @loadCombine1() {
enter:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
; CHECK: %[[D:.*]] = load i8, i8* %ptr, !invariant.group
%c = load i8, i8* %ptr
; CHECK-NOT: load
%d = load i8, i8* %ptr, !invariant.group !1
; CHECK: call void @bar(i8 %[[D]])
call void @bar(i8 %c)
; CHECK: call void @bar(i8 %[[D]])
call void @bar(i8 %d)
ret void
}
; CHECK-LABEL: define void @loadCombine2() {
define void @loadCombine2() {
enter:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group
%e = load i8, i8* %ptr, !invariant.group !1
; CHECK-NOT: load
%f = load i8, i8* %ptr
; CHECK: call void @bar(i8 %[[E]])
call void @bar(i8 %e)
; CHECK: call void @bar(i8 %[[E]])
call void @bar(i8 %f)
ret void
}
; CHECK-LABEL: define void @loadCombine3() {
define void @loadCombine3() {
enter:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group ![[OneMD:[0-9]]]
%e = load i8, i8* %ptr, !invariant.group !1
; CHECK-NOT: load
%f = load i8, i8* %ptr, !invariant.group !1
; CHECK: call void @bar(i8 %[[E]])
call void @bar(i8 %e)
; CHECK: call void @bar(i8 %[[E]])
call void @bar(i8 %f)
ret void
}
; CHECK-LABEL: define i8 @unoptimizable2() {
define i8 @unoptimizable2() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr
call void @foo(i8* %ptr)
%b = load i8, i8* %ptr, !invariant.group !0
; CHECK: ret i8 %a
ret i8 %a
}
; CHECK-LABEL: define i8 @unoptimizable3() {
define i8 @unoptimizable3() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
%ptr2 = call i8* @getPointer(i8* %ptr)
%a = load i8, i8* %ptr2, !invariant.group !0
; CHECK: ret i8 %a
ret i8 %a
}
; CHECK-LABEL: define i8 @unoptimizable4() {
define i8 @unoptimizable4() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
%ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
%a = load i8, i8* %ptr2, !invariant.group !0
; CHECK: ret i8 %a
ret i8 %a
}
; CHECK-LABEL: define i8 @volatile1() {
define i8 @volatile1() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0
%b = load volatile i8, i8* %ptr
; CHECK: call void @bar(i8 %b)
call void @bar(i8 %b)
%c = load volatile i8, i8* %ptr, !invariant.group !0
; FIXME: we could change %c to 42, preserving volatile load
; CHECK: call void @bar(i8 %c)
call void @bar(i8 %c)
; CHECK: ret i8 42
ret i8 %a
}
; CHECK-LABEL: define i8 @volatile2() {
define i8 @volatile2() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0
%b = load volatile i8, i8* %ptr
; CHECK: call void @bar(i8 %b)
call void @bar(i8 %b)
%c = load volatile i8, i8* %ptr, !invariant.group !0
; FIXME: we could change %c to 42, preserving volatile load
; CHECK: call void @bar(i8 %c)
call void @bar(i8 %c)
; CHECK: ret i8 42
ret i8 %a
}
; CHECK-LABEL: define i8 @fun() {
define i8 @fun() {
entry:
%ptr = alloca i8
store i8 42, i8* %ptr, !invariant.group !0
call void @foo(i8* %ptr)
%a = load i8, i8* %ptr, !invariant.group !0 ; Can assume that value under %ptr didn't change
; CHECK: call void @bar(i8 42)
call void @bar(i8 %a)
call void @foo(i8* %ptr)
%b = load i8, i8* %ptr, !invariant.group !1 ; Can't assume anything, because group changed
; CHECK: call void @bar(i8 %b)
call void @bar(i8 %b)
%newPtr = call i8* @getPointer(i8* %ptr)
%c = load i8, i8* %newPtr, !invariant.group !0 ; Can't assume anything, because we only have information about %ptr
; CHECK: call void @bar(i8 %c)
call void @bar(i8 %c)
%unknownValue = load i8, i8* @unknownPtr
; FIXME: Can assume that %unknownValue == 42
; CHECK: store i8 %unknownValue, i8* %ptr, !invariant.group !0
store i8 %unknownValue, i8* %ptr, !invariant.group !0
%newPtr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
%d = load i8, i8* %newPtr2, !invariant.group !0 ; Can't step through invariant.group.barrier to get value of %ptr
; CHECK: ret i8 %d
ret i8 %d
}
[MemDep] Handle gep with zeros for invariant.group Summary: gep 0, 0 is equivalent to bitcast. LLVM canonicalizes it to getelementptr because it make SROA can then handle it. Simple case like void g(A &a) { z(a); if (glob) a.foo(); } void testG() { A a; g(a); } was not devirtualized with -fstrict-vtable-pointers because luck of handling for gep 0 in Memory Dependence Analysis Reviewers: dberlin, nlewycky, chandlerc Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D28126 llvm-svn: 290763
2016-12-31 02:45:07 +08:00
; This test checks if invariant.group understands gep with zeros
; CHECK-LABEL: define void @testGEP0() {
define void @testGEP0() {
%a = alloca %struct.A, align 8
%1 = bitcast %struct.A* %a to i8*
%2 = getelementptr inbounds %struct.A, %struct.A* %a, i64 0, i32 0
store i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2) to i32 (...)**), i32 (...)*** %2, align 8, !invariant.group !0
; CHECK: call void @_ZN1A3fooEv(%struct.A* nonnull dereferenceable(8) %a)
call void @_ZN1A3fooEv(%struct.A* nonnull dereferenceable(8) %a) ; This call may change vptr
%3 = load i8, i8* @unknownPtr, align 4
%4 = icmp eq i8 %3, 0
br i1 %4, label %_Z1gR1A.exit, label %5
; This should be devirtualized by invariant.group
%6 = bitcast %struct.A* %a to void (%struct.A*)***
%7 = load void (%struct.A*)**, void (%struct.A*)*** %6, align 8, !invariant.group !0
%8 = load void (%struct.A*)*, void (%struct.A*)** %7, align 8
; CHECK: call void @_ZN1A3fooEv(%struct.A* nonnull %a)
call void %8(%struct.A* nonnull %a)
br label %_Z1gR1A.exit
_Z1gR1A.exit: ; preds = %0, %5
ret void
}
[MemDep] NFC walk invariant.group graph only down Summary: By using stripPointerCasts we can get to the root value and then walk down the bitcast graph Reviewers: reames Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D28181 llvm-svn: 291405
2017-01-09 06:26:06 +08:00
; Check if no optimizations are performed with global pointers.
; FIXME: we could do the optimizations if we would check if dependency comes
; from the same function.
; CHECK-LABEL: define void @testGlobal() {
define void @testGlobal() {
; CHECK: %a = load i8, i8* @unknownPtr, !invariant.group !0
%a = load i8, i8* @unknownPtr, !invariant.group !0
call void @foo2(i8* @unknownPtr, i8 %a)
; CHECK: %1 = load i8, i8* @unknownPtr, !invariant.group !0
%1 = load i8, i8* @unknownPtr, !invariant.group !0
call void @bar(i8 %1)
%b0 = bitcast i8* @unknownPtr to i1*
call void @fooBit(i1* %b0, i1 1)
; Adding regex because of canonicalization of bitcasts
; CHECK: %2 = load i1, i1* {{.*}}, !invariant.group !0
%2 = load i1, i1* %b0, !invariant.group !0
call void @fooBit(i1* %b0, i1 %2)
; CHECK: %3 = load i1, i1* {{.*}}, !invariant.group !0
%3 = load i1, i1* %b0, !invariant.group !0
call void @fooBit(i1* %b0, i1 %3)
ret void
}
; And in the case it is not global
; CHECK-LABEL: define void @testNotGlobal() {
define void @testNotGlobal() {
%a = alloca i8
call void @foo(i8* %a)
; CHECK: %b = load i8, i8* %a, !invariant.group !0
%b = load i8, i8* %a, !invariant.group !0
call void @foo2(i8* %a, i8 %b)
%1 = load i8, i8* %a, !invariant.group !0
; CHECK: call void @bar(i8 %b)
call void @bar(i8 %1)
%b0 = bitcast i8* %a to i1*
call void @fooBit(i1* %b0, i1 1)
; CHECK: %trunc = trunc i8 %b to i1
%2 = load i1, i1* %b0, !invariant.group !0
; CHECK-NEXT: call void @fooBit(i1* %b0, i1 %trunc)
call void @fooBit(i1* %b0, i1 %2)
%3 = load i1, i1* %b0, !invariant.group !0
; CHECK-NEXT: call void @fooBit(i1* %b0, i1 %trunc)
call void @fooBit(i1* %b0, i1 %3)
ret void
}
[Devirtualization] MemDep returns non-local !invariant.group dependencies Summary: Memory Dependence Analysis was limited to return only local dependencies for invariant.group handling. Now it returns NonLocal when it finds it and then by asking getNonLocalPointerDependency we get found dep. Thanks to this we are able to devirtualize loops! void indirect(A &a, int n) { for (int i = 0 ; i < n; i++) a.foo(); } void test(int n) { A a; indirect(a); } After inlining a.foo() will be changed to direct call, even if foo and A::A() is external (but only if vtable definition is be available). Reviewers: nlewycky, dberlin, chandlerc, rsmith Subscribers: mehdi_amini, davide, llvm-commits Differential Revision: https://reviews.llvm.org/D28137 llvm-svn: 291762
2017-01-12 19:33:58 +08:00
; CHECK-LABEL: define void @handling_loops()
define void @handling_loops() {
%a = alloca %struct.A, align 8
%1 = bitcast %struct.A* %a to i8*
%2 = getelementptr inbounds %struct.A, %struct.A* %a, i64 0, i32 0
store i32 (...)** bitcast (i8** getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2) to i32 (...)**), i32 (...)*** %2, align 8, !invariant.group !0
%3 = load i8, i8* @unknownPtr, align 4
%4 = icmp sgt i8 %3, 0
br i1 %4, label %.lr.ph.i, label %_Z2g2R1A.exit
.lr.ph.i: ; preds = %0
%5 = bitcast %struct.A* %a to void (%struct.A*)***
%6 = load i8, i8* @unknownPtr, align 4
%7 = icmp sgt i8 %6, 1
br i1 %7, label %._crit_edge.preheader, label %_Z2g2R1A.exit
._crit_edge.preheader: ; preds = %.lr.ph.i
br label %._crit_edge
._crit_edge: ; preds = %._crit_edge.preheader, %._crit_edge
%8 = phi i8 [ %10, %._crit_edge ], [ 1, %._crit_edge.preheader ]
%.pre = load void (%struct.A*)**, void (%struct.A*)*** %5, align 8, !invariant.group !0
%9 = load void (%struct.A*)*, void (%struct.A*)** %.pre, align 8
; CHECK: call void @_ZN1A3fooEv(%struct.A* nonnull %a)
call void %9(%struct.A* nonnull %a) #3
; CHECK-NOT: call void %
%10 = add nuw nsw i8 %8, 1
%11 = load i8, i8* @unknownPtr, align 4
%12 = icmp slt i8 %10, %11
br i1 %12, label %._crit_edge, label %_Z2g2R1A.exit.loopexit
_Z2g2R1A.exit.loopexit: ; preds = %._crit_edge
br label %_Z2g2R1A.exit
_Z2g2R1A.exit: ; preds = %_Z2g2R1A.exit.loopexit, %.lr.ph.i, %0
ret void
}
[MemDep] NFC walk invariant.group graph only down Summary: By using stripPointerCasts we can get to the root value and then walk down the bitcast graph Reviewers: reames Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D28181 llvm-svn: 291405
2017-01-09 06:26:06 +08:00
[GVN] Initial check-in of a new global value numbering algorithm. The code have been developed by Daniel Berlin over the years, and the new implementation goal is that of addressing shortcomings of the current GVN infrastructure, i.e. long compile time for large testcases, lack of phi predication, no load/store value numbering etc... The current code just implements the "core" GVN algorithm, although other pieces (load coercion, phi handling, predicate system) are already implemented in a branch out of tree. Once the core is stable, we'll start adding pieces on top of the base framework. The test currently living in test/Transform/NewGVN are a copy of the ones in GVN, with proper `XFAIL` (missing features in NewGVN). A flag will be added in a future commit to enable NewGVN, so that interested parties can exercise this code easily. Differential Revision: https://reviews.llvm.org/D26224 llvm-svn: 290346
2016-12-23 00:03:48 +08:00
declare void @foo(i8*)
[MemDep] NFC walk invariant.group graph only down Summary: By using stripPointerCasts we can get to the root value and then walk down the bitcast graph Reviewers: reames Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D28181 llvm-svn: 291405
2017-01-09 06:26:06 +08:00
declare void @foo2(i8*, i8)
[GVN] Initial check-in of a new global value numbering algorithm. The code have been developed by Daniel Berlin over the years, and the new implementation goal is that of addressing shortcomings of the current GVN infrastructure, i.e. long compile time for large testcases, lack of phi predication, no load/store value numbering etc... The current code just implements the "core" GVN algorithm, although other pieces (load coercion, phi handling, predicate system) are already implemented in a branch out of tree. Once the core is stable, we'll start adding pieces on top of the base framework. The test currently living in test/Transform/NewGVN are a copy of the ones in GVN, with proper `XFAIL` (missing features in NewGVN). A flag will be added in a future commit to enable NewGVN, so that interested parties can exercise this code easily. Differential Revision: https://reviews.llvm.org/D26224 llvm-svn: 290346
2016-12-23 00:03:48 +08:00
declare void @bar(i8)
declare i8* @getPointer(i8*)
declare void @_ZN1A3fooEv(%struct.A*)
declare void @_ZN1AC1Ev(%struct.A*)
[MemDep] NFC walk invariant.group graph only down Summary: By using stripPointerCasts we can get to the root value and then walk down the bitcast graph Reviewers: reames Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D28181 llvm-svn: 291405
2017-01-09 06:26:06 +08:00
declare void @fooBit(i1*, i1)
[GVN] Initial check-in of a new global value numbering algorithm. The code have been developed by Daniel Berlin over the years, and the new implementation goal is that of addressing shortcomings of the current GVN infrastructure, i.e. long compile time for large testcases, lack of phi predication, no load/store value numbering etc... The current code just implements the "core" GVN algorithm, although other pieces (load coercion, phi handling, predicate system) are already implemented in a branch out of tree. Once the core is stable, we'll start adding pieces on top of the base framework. The test currently living in test/Transform/NewGVN are a copy of the ones in GVN, with proper `XFAIL` (missing features in NewGVN). A flag will be added in a future commit to enable NewGVN, so that interested parties can exercise this code easily. Differential Revision: https://reviews.llvm.org/D26224 llvm-svn: 290346
2016-12-23 00:03:48 +08:00
declare i8* @llvm.invariant.group.barrier(i8*)
; Function Attrs: nounwind
declare void @llvm.assume(i1 %cmp.vtables) #0
attributes #0 = { nounwind }
; CHECK: ![[OneMD]] = !{!"other ptr"}
!0 = !{!"magic ptr"}
!1 = !{!"other ptr"}
!2 = !{!"vtable_of_a"}