6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-07-22 09:29:31 +00:00
Code Issues Projects Releases Wiki Activity

[RewriteStatepointsForGC] Strip deref info after rewriting.

Browse Source 
Summary:
Once a gc.statepoint has been rewritten to relocate live references, the
SSA values represent physical pointers instead of logical references.
Logical dereferencability does not imply physical dereferencability and
after RewriteStatepointsForGC has run any attributes that imply
dereferencability of the logical references need to be stripped.

This current approach is conservative, and can be made more precise
later if needed.  For starters, we need to strip dereferencable
attributes only from pointers that live in the GC address space.

Reviewers: reames, pgavlin

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D10105

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@238883 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sanjoy Das 2015-06-02 22:33:37 +00:00
parent e9609875ee
commit f73780ec1a
2 changed files with 179 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

102
lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
View File

@ -30,6 +30,7 @@
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/IR/Statepoint.h"
#include "llvm/IR/Value.h"
#include "llvm/IR/Verifier.h"
@ -85,6 +86,14 @@ struct RewriteStatepointsForGC : public ModulePass {
bool Changed = false;
for (Function &F : M)
Changed |= runOnFunction(F);
if (Changed) {
// stripDereferenceabilityInfo asserts that shouldRewriteStatepointsIn
// returns true for at least one function in the module. Since at least
// one function changed, we know that the precondition is satisfied.
stripDereferenceabilityInfo(M);
}
return Changed;
}
@ -94,6 +103,20 @@ struct RewriteStatepointsForGC : public ModulePass {
AU.addRequired<DominatorTreeWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
}
/// The IR fed into RewriteStatepointsForGC may have had attributes implying
/// dereferenceability that are no longer valid/correct after
/// RewriteStatepointsForGC has run. This is because semantically, after
/// RewriteStatepointsForGC runs, all calls to gc.statepoint "free" the entire
/// heap. stripDereferenceabilityInfo (conservatively) restores correctness
/// by erasing all attributes in the module that externally imply
/// dereferenceability.
///
void stripDereferenceabilityInfo(Module &M);
// Helpers for stripDereferenceabilityInfo
void stripDereferenceabilityInfoFromBody(Function &F);
void stripDereferenceabilityInfoFromPrototype(Function &F);
};
} // namespace
@ -2200,6 +2223,72 @@ static bool insertParsePoints(Function &F, DominatorTree &DT, Pass *P,
return !records.empty();
}
// Handles both return values and arguments for Functions and CallSites.
template <typename AttrHolder>
static void RemoveDerefAttrAtIndex(LLVMContext &Ctx, AttrHolder &AH,
unsigned Index) {
AttrBuilder R;
if (AH.getDereferenceableBytes(Index))
R.addAttribute(Attribute::get(Ctx, Attribute::Dereferenceable,
AH.getDereferenceableBytes(Index)));
if (AH.getDereferenceableOrNullBytes(Index))
R.addAttribute(Attribute::get(Ctx, Attribute::DereferenceableOrNull,
AH.getDereferenceableOrNullBytes(Index)));
if (!R.empty())
AH.setAttributes(AH.getAttributes().removeAttributes(
Ctx, Index, AttributeSet::get(Ctx, Index, R)));
};
void
RewriteStatepointsForGC::stripDereferenceabilityInfoFromPrototype(Function &F) {
LLVMContext &Ctx = F.getContext();
for (Argument &A : F.args())
if (isa<PointerType>(A.getType()))
RemoveDerefAttrAtIndex(Ctx, F, A.getArgNo() + 1);
if (isa<PointerType>(F.getReturnType()))
RemoveDerefAttrAtIndex(Ctx, F, AttributeSet::ReturnIndex);
}
void RewriteStatepointsForGC::stripDereferenceabilityInfoFromBody(Function &F) {
if (F.empty())
return;
LLVMContext &Ctx = F.getContext();
MDBuilder Builder(Ctx);
for (Instruction &I : inst_range(F)) {
if (const MDNode *MD = I.getMetadata(LLVMContext::MD_tbaa)) {
assert(MD->getNumOperands() < 5 && "unrecognized metadata shape!");
bool IsImmutableTBAA =
MD->getNumOperands() == 4 &&
mdconst::extract<ConstantInt>(MD->getOperand(3))->getValue() == 1;
if (!IsImmutableTBAA)
continue; // no work to do, MD_tbaa is already marked mutable
MDNode *Base = cast<MDNode>(MD->getOperand(0));
MDNode *Access = cast<MDNode>(MD->getOperand(1));
uint64_t Offset =
mdconst::extract<ConstantInt>(MD->getOperand(2))->getZExtValue();
MDNode *MutableTBAA =
Builder.createTBAAStructTagNode(Base, Access, Offset);
I.setMetadata(LLVMContext::MD_tbaa, MutableTBAA);
}
if (CallSite CS = CallSite(&I)) {
for (int i = 0, e = CS.arg_size(); i != e; i++)
if (isa<PointerType>(CS.getArgument(i)->getType()))
RemoveDerefAttrAtIndex(Ctx, CS, i + 1);
if (isa<PointerType>(CS.getType()))
RemoveDerefAttrAtIndex(Ctx, CS, AttributeSet::ReturnIndex);
}
}
}
/// Returns true if this function should be rewritten by this pass. The main
/// point of this function is as an extension point for custom logic.
static bool shouldRewriteStatepointsIn(Function &F) {
@ -2214,6 +2303,19 @@ static bool shouldRewriteStatepointsIn(Function &F) {
return false;
}
void RewriteStatepointsForGC::stripDereferenceabilityInfo(Module &M) {
#ifndef NDEBUG
assert(std::any_of(M.begin(), M.end(), shouldRewriteStatepointsIn) &&
"precondition!");
#endif
for (Function &F : M)
stripDereferenceabilityInfoFromPrototype(F);
for (Function &F : M)
stripDereferenceabilityInfoFromBody(F);
}
bool RewriteStatepointsForGC::runOnFunction(Function &F) {
// Nothing to do for declarations.
if (F.isDeclaration() || F.empty())

77
test/Transforms/RewriteStatepointsForGC/deref-pointers.ll Normal file
View File

@ -0,0 +1,77 @@
; RUN: opt -S -rewrite-statepoints-for-gc < %s | FileCheck %s
declare void @foo()
declare i8 addrspace(1)* @some_function()
declare void @some_function_consumer(i8 addrspace(1)*)
declare dereferenceable(4) i8 addrspace(1)* @some_function_ret_deref()
; CHECK: declare i8 addrspace(1)* @some_function_ret_deref()
define i8 addrspace(1)* @test_deref_arg(i8 addrspace(1)* dereferenceable(4) %a) gc "statepoint-example" {
; CHECK: define i8 addrspace(1)* @test_deref_arg(i8 addrspace(1)* %a)
entry:
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %a
}
define i8 addrspace(1)* @test_deref_or_null_arg(i8 addrspace(1)* dereferenceable_or_null(4) %a) gc "statepoint-example" {
; CHECK: define i8 addrspace(1)* @test_deref_or_null_arg(i8 addrspace(1)* %a)
entry:
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %a
}
define i8 addrspace(1)* @test_deref_retval() gc "statepoint-example" {
; CHECK-LABEL: @test_deref_retval(
entry:
%a = call dereferenceable(4) i8 addrspace(1)* @some_function()
; CHECK: %a = call i8 addrspace(1)* @some_function()
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %a
}
define i8 addrspace(1)* @test_deref_or_null_retval() gc "statepoint-example" {
; CHECK-LABEL: @test_deref_or_null_retval(
entry:
%a = call dereferenceable_or_null(4) i8 addrspace(1)* @some_function()
; CHECK: %a = call i8 addrspace(1)* @some_function()
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %a
}
define i8 @test_md(i8 addrspace(1)* %ptr) gc "statepoint-example" {
; CHECK-LABEL: @test_md(
entry:
; CHECK: %tmp = load i8, i8 addrspace(1)* %ptr, !tbaa !0
%tmp = load i8, i8 addrspace(1)* %ptr, !tbaa !0
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 %tmp
}
define i8 addrspace(1)* @test_decl_only_attribute(i8 addrspace(1)* %ptr) gc "statepoint-example" {
; CHECK-LABEL: @test_decl_only_attribute(
entry:
; No change here, but the prototype of some_function_ret_deref should have changed.
; CHECK: call i8 addrspace(1)* @some_function_ret_deref()
%a = call i8 addrspace(1)* @some_function_ret_deref()
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %a
}
define i8 addrspace(1)* @test_callsite_arg_attribute(i8 addrspace(1)* %ptr) gc "statepoint-example" {
; CHECK-LABEL: @test_callsite_arg_attribute(
entry:
; CHECK: call void @some_function_consumer(i8 addrspace(1)* %ptr)
call void @some_function_consumer(i8 addrspace(1)* dereferenceable(4) %ptr)
call i32 (i64, i32, void ()*, i32, i32, ...) @llvm.experimental.gc.statepoint.p0f_isVoidf(i64 0, i32 0, void ()* @foo, i32 0, i32 0, i32 0, i32 5, i32 0, i32 -1, i32 0, i32 0, i32 0)
ret i8 addrspace(1)* %ptr
}
declare i32 @llvm.experimental.gc.statepoint.p0f_isVoidf(i64, i32, void ()*, i32, i32, ...)
!0 = !{!1, !1, i64 0, i64 1}
!1 = !{!"red", !2}
!2 = !{!"blue"}
; CHECK: !0 = !{!1, !1, i64 0}
; CHECK: !1 = !{!"red", !2}
; CHECK: !2 = !{!"blue"}