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Fix support of gc_preserve intrinsics in the allocation optimization pass #23783

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Merged
merged 1 commit into from
Sep 22, 2017
Merged

Fix support of gc_preserve intrinsics in the allocation optimization pass #23783

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34 changes: 23 additions & 11 deletions src/llvm-alloc-opt.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,8 @@ static bool isBundleOperand(CallInst *call, unsigned idx)
*
* * load
* * `pointer_from_objref`
* * Any real llvm intrinsics
* * gc preserve intrinsics
* * `ccall` gcroot array (`jl_roots` operand bundle)
* * store (as address)
* * addrspacecast, bitcast, getelementptr
Expand All @@ -88,6 +90,7 @@ struct AllocOpt : public FunctionPass {
Function *ptr_from_objref;
Function *lifetime_start;
Function *lifetime_end;
Function *gc_preserve_begin;

Type *T_int8;
Type *T_int32;
Expand Down Expand Up @@ -150,7 +153,8 @@ struct AllocOpt : public FunctionPass {
bool checkInst(Instruction *I, CheckInstStack &stack, std::set<Instruction*> &uses,
bool &ignore_tag);
void replaceUsesWith(Instruction *orig_i, Instruction *new_i, ReplaceUsesStack &stack);
void replaceIntrinsicUseWith(IntrinsicInst *call, Instruction *orig_i, Instruction *new_i);
void replaceIntrinsicUseWith(IntrinsicInst *call, Intrinsic::ID ID, Instruction *orig_i,
Instruction *new_i);
bool isSafepoint(Instruction *inst);
void getAnalysisUsage(AnalysisUsage &AU) const override
{
Expand Down Expand Up @@ -333,6 +337,7 @@ bool AllocOpt::doInitialization(Module &M)
return false;

ptr_from_objref = M.getFunction("julia.pointer_from_objref");
gc_preserve_begin = M.getFunction("llvm.julia.gc_preserve_begin");

T_prjlvalue = alloc_obj->getReturnType();
T_pjlvalue = PointerType::get(cast<PointerType>(T_prjlvalue)->getElementType(), 0);
Expand Down Expand Up @@ -384,9 +389,16 @@ bool AllocOpt::checkInst(Instruction *I, CheckInstStack &stack, std::set<Instruc
if (auto call = dyn_cast<CallInst>(inst)) {
// TODO handle `memcmp`
// None of the intrinsics should care if the memory is stack or heap allocated.
if (isa<IntrinsicInst>(call))
return true;
if (ptr_from_objref && ptr_from_objref == call->getCalledFunction())
auto callee = call->getCalledFunction();
if (auto II = dyn_cast<IntrinsicInst>(call)) {
if (II->getIntrinsicID()) {
return true;
}
if (gc_preserve_begin && gc_preserve_begin == callee) {
return true;
}
}
if (ptr_from_objref && ptr_from_objref == callee)
return true;
auto opno = use->getOperandNo();
// Uses in `jl_roots` operand bundle are not counted as escaping, everything else is.
Expand Down Expand Up @@ -445,11 +457,9 @@ bool AllocOpt::checkInst(Instruction *I, CheckInstStack &stack, std::set<Instruc
}
}

void AllocOpt::replaceIntrinsicUseWith(IntrinsicInst *call, Instruction *orig_i,
Instruction *new_i)
void AllocOpt::replaceIntrinsicUseWith(IntrinsicInst *call, Intrinsic::ID ID,
Instruction *orig_i, Instruction *new_i)
{
Intrinsic::ID ID = call->getIntrinsicID();
assert(ID);
auto nargs = call->getNumArgOperands();
SmallVector<Value*, 8> args(nargs);
SmallVector<Type*, 8> argTys(nargs);
Expand Down Expand Up @@ -549,10 +559,12 @@ void AllocOpt::replaceUsesWith(Instruction *orig_inst, Instruction *new_inst,
return;
}
if (auto intrinsic = dyn_cast<IntrinsicInst>(call)) {
replaceIntrinsicUseWith(intrinsic, orig_i, new_i);
return;
if (Intrinsic::ID ID = intrinsic->getIntrinsicID()) {
replaceIntrinsicUseWith(intrinsic, ID, orig_i, new_i);
return;
}
}
// remove from operand bundle
// remove from operand bundle or arguments for gc_perserve_begin
Type *new_t = new_i->getType();
user->replaceUsesOfWith(orig_i, ConstantPointerNull::get(cast<PointerType>(new_t)));
}
Expand Down
2 changes: 2 additions & 0 deletions src/llvm-late-gc-lowering.cpp
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Expand Up @@ -764,6 +764,8 @@ State LateLowerGCFrame::LocalScan(Function &F) {
std::vector<int> args;
for (Use &U : CI->arg_operands()) {
Value *V = U;
if (isa<Constant>(V))
continue;
int Num = Number(S, V);
if (Num >= 0)
args.push_back(Num);
Expand Down
13 changes: 13 additions & 0 deletions test/codegen.jl
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Expand Up @@ -188,6 +188,13 @@ function two_breakpoint(a::Float64)
ccall(:jl_breakpoint, Void, (Ref{Float64},), a)
end

function load_dummy_ref(x::Int)
r = Ref{Int}(x)
Base.@gc_preserve r begin
unsafe_load(Ptr{Int}(pointer_from_objref(r)))
end
end

if opt_level > 0
breakpoint_f64_ir = get_llvm((a)->ccall(:jl_breakpoint, Void, (Ref{Float64},), a),
Tuple{Float64})
Expand All @@ -198,6 +205,12 @@ if opt_level > 0
two_breakpoint_ir = get_llvm(two_breakpoint, Tuple{Float64})
@test !contains(two_breakpoint_ir, "jl_gc_pool_alloc")
@test contains(two_breakpoint_ir, "llvm.lifetime.end")

@test load_dummy_ref(1234) === 1234
load_dummy_ref_ir = get_llvm(load_dummy_ref, Tuple{Int})
@test !contains(load_dummy_ref_ir, "jl_gc_pool_alloc")
# Hopefully this is reliable enough. LLVM should be able to optimize this to a direct return.
@test contains(load_dummy_ref_ir, "ret $Iptr %0")
end

# Issue 22770
Expand Down
20 changes: 20 additions & 0 deletions test/llvmpasses/alloc-opt.jl
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Expand Up @@ -205,6 +205,25 @@ top:
""")
# CHECK-LABEL: }

# CHECK-LABEL: @preserve_opt
# CHECK: alloca i128, align 16
# CHECK: call %jl_value_t*** @jl_get_ptls_states()
# CHECK-NOT: @julia.gc_alloc_obj
# CHECK-NOT: @jl_gc_pool_alloc
println("""
define void @preserve_opt(i8* %v22) {
top:
%v6 = call %jl_value_t*** @jl_get_ptls_states()
%v18 = bitcast %jl_value_t*** %v6 to i8*
%v19 = call noalias %jl_value_t addrspace(10)* @julia.gc_alloc_obj(i8* %v18, $isz 16, %jl_value_t addrspace(10)* @tag)
%v20 = bitcast %jl_value_t addrspace(10)* %v19 to i8 addrspace(10)*
%v21 = addrspacecast i8 addrspace(10)* %v20 to i8 addrspace(11)*
%tok = call token (...) @llvm.julia.gc_preserve_begin(%jl_value_t addrspace(10)* %v19)
ret void
}
""")
# CHECK-LABEL: }

# CHECK: declare noalias %jl_value_t addrspace(10)* @jl_gc_pool_alloc(i8*,
# CHECK: declare noalias %jl_value_t addrspace(10)* @jl_gc_big_alloc(i8*,
println("""
Expand All @@ -213,6 +232,7 @@ declare %jl_value_t*** @jl_get_ptls_states()
declare noalias %jl_value_t addrspace(10)* @julia.gc_alloc_obj(i8*, $isz, %jl_value_t addrspace(10)*)
declare i64 @julia.pointer_from_objref(%jl_value_t addrspace(11)*)
declare void @llvm.memcpy.p11i8.p0i8.i64(i8 addrspace(11)* nocapture writeonly, i8* nocapture readonly, i64, i32, i1)
declare token @llvm.julia.gc_preserve_begin(...)

!0 = !{!1, !1, i64 0}
!1 = !{!"jtbaa_tag", !2, i64 0}
Expand Down