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[Attributor] Use nofree argument attribute for heap-to-stack conversion 

Reviewers: jdoerfert, uenoku

Subscribers:

Differential Revision: https://reviews.llvm.org/D70140
This commit is contained in:
Stefan Stipanovic 2019-11-17 21:35:04 +01:00
parent ebf9bf2cbc
commit a516fbac52
2 changed files with 25 additions and 11 deletions
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16
llvm/lib/Transforms/IPO/Attributor.cpp
View File

@ -4155,11 +4155,6 @@ ChangeStatus AAHeapToStackImpl::updateImpl(Attributor &A) {
continue;
}
// NOTE: Right now, if a function that has malloc pointer as an argument
// frees memory, we assume that the malloc pointer is freed.
// TODO: Add nofree callsite argument attribute to indicate that pointer
// argument is not freed.
if (auto *CB = dyn_cast<CallBase>(UserI)) {
if (!CB->isArgOperand(U))
continue;
@ -4180,15 +4175,16 @@ ChangeStatus AAHeapToStackImpl::updateImpl(Attributor &A) {
continue;
}
// If a function does not free memory we are fine
const auto &NoFreeAA =
A.getAAFor<AANoFree>(*this, IRPosition::callsite_function(*CB));
unsigned ArgNo = CB->getArgOperandNo(U);
const auto &NoCaptureAA = A.getAAFor<AANoCapture>(
*this, IRPosition::callsite_argument(*CB, ArgNo));
if (!NoCaptureAA.isAssumedNoCapture() || !NoFreeAA.isAssumedNoFree()) {
// If a callsite argument use is nofree, we are fine.
const auto &ArgNoFreeAA = A.getAAFor<AANoFree>(
*this, IRPosition::callsite_argument(*CB, ArgNo));
if (!NoCaptureAA.isAssumedNoCapture() || !ArgNoFreeAA.isAssumedNoFree()) {
LLVM_DEBUG(dbgs() << "[H2S] Bad user: " << *UserI << "\n");
ValidUsesOnly = false;
}

20
llvm/test/Transforms/FunctionAttrs/heap_to_stack.ll
View File

@ -24,6 +24,13 @@ declare void @free(i8* nocapture)
declare void @llvm.lifetime.start.p0i8(i64, i8* nocapture) nounwind
; CHECK: @nofree_arg_only(i8* nocapture nofree %p1, i8* nocapture %p2)
define void @nofree_arg_only(i8* %p1, i8* %p2) {
tail call void @free(i8* %p2)
tail call void @nofree_func(i8* %p1)
ret void
}
; TEST 1 - negative, pointer freed in another function.
define void @test1() {
@ -59,6 +66,16 @@ define void @test3() {
ret void
}
define void @test3a(i8* %p) {
%1 = tail call noalias i8* @malloc(i64 4)
; CHECK: %1 = alloca i8, i64 4
; CHECK-NEXT: tail call void @nofree_arg_only
tail call void @nofree_arg_only(i8* %1, i8* %p)
; CHECK-NOT: @free(i8* %1)
tail call void @free(i8* %1)
ret void
}
declare noalias i8* @calloc(i64, i64)
define void @test0() {
@ -85,7 +102,7 @@ define void @test4() {
; TEST 5 - not all exit paths have a call to free, but all uses of malloc
; are in nofree functions and are not captured
define void @test5(i32) {
define void @test5(i32, i8* %p) {
%2 = tail call noalias i8* @malloc(i64 4)
; CHECK: %2 = alloca i8, i64 4
; CHECK-NEXT: icmp eq i32 %0, 0
@ -97,6 +114,7 @@ define void @test5(i32) {
br label %6
5: ; preds = %1
tail call void @nofree_arg_only(i8* %2, i8* %p)
tail call void @free(i8* %2)
; CHECK-NOT: @free(i8* %2)
br label %6