[llvm] r369470 - [Attributor] Liveness for internal functions.
Stefan Stipanovic via llvm-commits
llvm-commits at lists.llvm.org
Tue Aug 20 16:16:57 PDT 2019
Author: sstefan
Date: Tue Aug 20 16:16:57 2019
New Revision: 369470
URL: http://llvm.org/viewvc/llvm-project?rev=369470&view=rev
Log:
[Attributor] Liveness for internal functions.
For an internal function, if all its call sites are dead, the body of the function is considered dead.
Reviewers: jdoerfert, uenoku
Subscribers: hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D66155
Modified:
llvm/trunk/include/llvm/Transforms/IPO/Attributor.h
llvm/trunk/lib/Transforms/IPO/Attributor.cpp
llvm/trunk/test/Transforms/FunctionAttrs/align.ll
llvm/trunk/test/Transforms/FunctionAttrs/liveness.ll
llvm/trunk/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
Modified: llvm/trunk/include/llvm/Transforms/IPO/Attributor.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/IPO/Attributor.h?rev=369470&r1=369469&r2=369470&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/IPO/Attributor.h (original)
+++ llvm/trunk/include/llvm/Transforms/IPO/Attributor.h Tue Aug 20 16:16:57 2019
@@ -297,6 +297,9 @@ struct IRPosition {
if (auto *Arg = dyn_cast<Argument>(&V))
if (!Arg->getParent()->isDeclaration())
return &Arg->getParent()->getEntryBlock().front();
+ if (auto *F = dyn_cast<Function>(&V))
+ if (!F->isDeclaration())
+ return &(F->getEntryBlock().front());
return nullptr;
}
const Instruction *getCtxI() const {
Modified: llvm/trunk/lib/Transforms/IPO/Attributor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/Attributor.cpp?rev=369470&r1=369469&r2=369470&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/Attributor.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/Attributor.cpp Tue Aug 20 16:16:57 2019
@@ -1570,13 +1570,22 @@ struct AAIsDeadImpl : public AAIsDead {
void initialize(Attributor &A) override {
const Function *F = getAssociatedFunction();
+
+ if (F->hasInternalLinkage())
+ return;
+
if (!F || !F->hasExactDefinition()) {
indicatePessimisticFixpoint();
return;
}
+ exploreFromEntry(A, F);
+ }
+
+ void exploreFromEntry(Attributor &A, const Function *F) {
ToBeExploredPaths.insert(&(F->getEntryBlock().front()));
AssumedLiveBlocks.insert(&(F->getEntryBlock()));
+
for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
if (const Instruction *NextNoReturnI =
findNextNoReturn(A, ToBeExploredPaths[i]))
@@ -1606,7 +1615,12 @@ struct AAIsDeadImpl : public AAIsDead {
"Attempted to manifest an invalid state!");
ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
- const Function &F = *getAssociatedFunction();
+ Function &F = *getAssociatedFunction();
+
+ if (AssumedLiveBlocks.empty()) {
+ F.replaceAllUsesWith(UndefValue::get(F.getType()));
+ return ChangeStatus::CHANGED;
+ }
// Flag to determine if we can change an invoke to a call assuming the
// callee is nounwind. This is not possible if the personality of the
@@ -1725,6 +1739,13 @@ struct AAIsDeadFunction final : public A
/// See AbstractAttribute::trackStatistics()
void trackStatistics() const override {
+ STATS_DECL(DeadInternalFunction, Function,
+ "Number of internal functions classified as dead (no live callsite)");
+ BUILD_STAT_NAME(DeadInternalFunction, Function) +=
+ (getAssociatedFunction()->hasInternalLinkage() &&
+ AssumedLiveBlocks.empty())
+ ? 1
+ : 0;
STATS_DECL(DeadBlocks, Function,
"Number of basic blocks classified as dead");
BUILD_STAT_NAME(DeadBlocks, Function) +=
@@ -1796,10 +1817,25 @@ const Instruction *AAIsDeadImpl::findNex
}
ChangeStatus AAIsDeadImpl::updateImpl(Attributor &A) {
+ const Function *F = getAssociatedFunction();
+ ChangeStatus Status = ChangeStatus::UNCHANGED;
+
+ if (F->hasInternalLinkage() && AssumedLiveBlocks.empty()) {
+ auto CallSiteCheck = [&](CallSite) { return false; };
+
+ // All callsites of F are dead.
+ if (A.checkForAllCallSites(CallSiteCheck, *this, true))
+ return ChangeStatus::UNCHANGED;
+
+ // There exists at least one live call site, so we explore the function.
+ Status = ChangeStatus::CHANGED;
+
+ exploreFromEntry(A, F);
+ }
+
// Temporary collection to iterate over existing noreturn instructions. This
// will alow easier modification of NoReturnCalls collection
SmallVector<const Instruction *, 8> NoReturnChanged;
- ChangeStatus Status = ChangeStatus::UNCHANGED;
for (const Instruction *I : NoReturnCalls)
NoReturnChanged.push_back(I);
@@ -2249,6 +2285,11 @@ bool Attributor::isAssumedDead(const Abs
if (!LivenessAA)
LivenessAA =
&getAAFor<AAIsDead>(AA, IRPosition::function(*CtxI->getFunction()));
+
+ // Don't check liveness for AAIsDead.
+ if (&AA == LivenessAA)
+ return false;
+
if (!LivenessAA->isAssumedDead(CtxI))
return false;
Modified: llvm/trunk/test/Transforms/FunctionAttrs/align.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/align.ll?rev=369470&r1=369469&r2=369470&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/align.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/align.ll Tue Aug 20 16:16:57 2019
@@ -139,6 +139,7 @@ define internal i8* @f3(i8* readnone %0)
; Better than IR information
; ATTRIBUTOR: define align 32 i32* @test7(i32* returned align 32 %p)
define align 4 i32* @test7(i32* align 32 %p) #0 {
+ tail call i8* @f1(i8* align 8 dereferenceable(1) @a1)
ret i32* %p
}
Modified: llvm/trunk/test/Transforms/FunctionAttrs/liveness.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/liveness.ll?rev=369470&r1=369469&r2=369470&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/liveness.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/liveness.ll Tue Aug 20 16:16:57 2019
@@ -12,6 +12,27 @@ declare i32 @foo_noreturn() noreturn
declare i32 @bar() nosync readnone
+; This internal function has no live call sites, so all its BBs are considered dead,
+; and nothing should be deduced for it.
+
+; CHECK: define internal i32 @dead_internal_func(i32 %0)
+define internal i32 @dead_internal_func(i32 %0) {
+ %2 = icmp slt i32 %0, 1
+ br i1 %2, label %3, label %5
+
+; <label>:3: ; preds = %5, %1
+ %4 = phi i32 [ 1, %1 ], [ %8, %5 ]
+ ret i32 %4
+
+; <label>:5: ; preds = %1, %5
+ %6 = phi i32 [ %9, %5 ], [ 1, %1 ]
+ %7 = phi i32 [ %8, %5 ], [ 1, %1 ]
+ %8 = mul nsw i32 %6, %7
+ %9 = add nuw nsw i32 %6, 1
+ %10 = icmp eq i32 %6, %0
+ br i1 %10, label %3, label %5
+}
+
; CHECK: Function Attrs: nofree norecurse nounwind uwtable willreturn
define i32 @volatile_load(i32*) norecurse nounwind uwtable {
%2 = load volatile i32, i32* %0, align 4
@@ -35,6 +56,8 @@ entry:
call void @no_return_call()
; CHECK: call void @no_return_call()
; CHECK-NEXT: unreachable
+ call i32 @dead_internal_func(i32 10)
+ ; CHECK call i32 undef(i32 10)
%cmp = icmp eq i32 %a, 0
br i1 %cmp, label %cond.true, label %cond.false
@@ -96,6 +119,8 @@ cond.true:
call void @no_return_call()
; CHECK: call void @no_return_call()
; CHECK-NEXT: unreachable
+ call i32 @dead_internal_func(i32 10)
+ ; CHECK call i32 undef(i32 10)
%call = call i32 @foo()
br label %cond.end
@@ -103,6 +128,8 @@ cond.false:
call void @no_return_call()
; CHECK: call void @no_return_call()
; CHECK-NEXT: unreachable
+ call i32 @dead_internal_func(i32 10)
+ ; CHECK call i32 undef(i32 10)
%call1 = call i32 @bar()
br label %cond.end
@@ -311,3 +338,73 @@ cond.end:
%8 = phi i32 [ %1, %cond.elseif ], [ 0, %cond.else ], [ 0, %cond.if ]
ret i32 %8
}
+
+; SCC test
+;
+; char a1 __attribute__((aligned(8)));
+; char a2 __attribute__((aligned(16)));
+;
+; char* f1(char* a ){
+; return a?a:f2(&a1);
+; }
+; char* f2(char* a){
+; return a?f1(a):f3(&a2);
+; }
+;
+; char* f3(char* a){
+; return a?&a1: f1(&a2);
+; }
+
+ at a1 = common global i8 0, align 8
+ at a2 = common global i8 0, align 16
+
+define internal i8* @f1(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f1(i8* readnone %0)
+ %2 = icmp eq i8* %0, null
+ br i1 %2, label %3, label %5
+
+; <label>:3: ; preds = %1
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 8 @a1)
+ %4 = tail call i8* @f2(i8* nonnull @a1)
+ br label %5
+
+; <label>:5: ; preds = %1, %3
+ %6 = phi i8* [ %4, %3 ], [ %0, %1 ]
+ ret i8* %6
+}
+
+define internal i8* @f2(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f2(i8* readnone %0)
+ %2 = icmp eq i8* %0, null
+ br i1 %2, label %5, label %3
+
+; <label>:3: ; preds = %1
+
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 8 %0)
+ %4 = tail call i8* @f1(i8* nonnull %0)
+ br label %7
+
+; <label>:5: ; preds = %1
+; ATTRIBUTOR: %6 = tail call i8* undef(i8* nonnull align 16 @a2)
+ %6 = tail call i8* @f3(i8* nonnull @a2)
+ br label %7
+
+; <label>:7: ; preds = %5, %3
+ %8 = phi i8* [ %4, %3 ], [ %6, %5 ]
+ ret i8* %8
+}
+
+define internal i8* @f3(i8* readnone %0) local_unnamed_addr #0 {
+; ATTRIBUTOR: define internal i8* @f3(i8* readnone %0)
+ %2 = icmp eq i8* %0, null
+ br i1 %2, label %3, label %5
+
+; <label>:3: ; preds = %1
+; ATTRIBUTOR: %4 = tail call i8* undef(i8* nonnull align 16 @a2)
+ %4 = tail call i8* @f1(i8* nonnull @a2)
+ br label %5
+
+; <label>:5: ; preds = %1, %3
+ %6 = phi i8* [ %4, %3 ], [ @a1, %1 ]
+ ret i8* %6
+}
Modified: llvm/trunk/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll?rev=369470&r1=369469&r2=369470&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll (original)
+++ llvm/trunk/test/Transforms/FunctionAttrs/read_write_returned_arguments_scc.ll Tue Aug 20 16:16:57 2019
@@ -1,4 +1,4 @@
-; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-disable=false -S < %s | FileCheck %s
+; RUN: opt -functionattrs -enable-nonnull-arg-prop -attributor -attributor-disable=false -attributor-max-iterations=33 -S < %s | FileCheck %s
;
; This is an evolved example to stress test SCC parameter attribute propagation.
; The SCC in this test is made up of the following six function, three of which
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