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NewGVN: Fix PR 31501.

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Summary: LLVM's non-standard notion of phi nodes means we can't both try to substitute for undef in phi nodes *and* use phi nodes as leaders all the time. This changes NewGVN to use the same semantics as SimplifyPHINode to decide which phi nodes are equivalent.

Reviewers: davide

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D28312

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@291308 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Daniel Berlin 2017-01-07 00:01:42 +00:00
parent 64d3b81d23
commit 45b7d44c62
3 changed files with 223 additions and 38 deletions
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88
lib/Transforms/Scalar/NewGVN.cpp
View File

@ -390,10 +390,10 @@ INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass)
INITIALIZE_PASS_END(NewGVN, "newgvn", "Global Value Numbering", false, false)
PHIExpression *NewGVN::createPHIExpression(Instruction *I) {
BasicBlock *PhiBlock = I->getParent();
BasicBlock *PHIBlock = I->getParent();
auto *PN = cast<PHINode>(I);
auto *E = new (ExpressionAllocator)
PHIExpression(PN->getNumOperands(), I->getParent());
auto *E =
new (ExpressionAllocator) PHIExpression(PN->getNumOperands(), PHIBlock);
E->allocateOperands(ArgRecycler, ExpressionAllocator);
E->setType(I->getType());
@ -408,10 +408,10 @@ PHIExpression *NewGVN::createPHIExpression(Instruction *I) {
std::transform(Filtered.begin(), Filtered.end(), op_inserter(E),
[&](const Use &U) -> Value * {
// Don't try to transform self-defined phis
// Don't try to transform self-defined phis.
if (U == PN)
return PN;
const BasicBlockEdge BBE(PN->getIncomingBlock(U), PhiBlock);
const BasicBlockEdge BBE(PN->getIncomingBlock(U), PHIBlock);
return lookupOperandLeader(U, I, BBE);
});
return E;
@ -810,36 +810,50 @@ bool NewGVN::setMemoryAccessEquivTo(MemoryAccess *From, MemoryAccess *To) {
const Expression *NewGVN::performSymbolicPHIEvaluation(Instruction *I,
const BasicBlock *B) {
auto *E = cast<PHIExpression>(createPHIExpression(I));
if (E->op_empty()) {
// We match the semantics of SimplifyPhiNode from InstructionSimplify here.
// See if all arguaments are the same.
// We track if any were undef because they need special handling.
bool HasUndef = false;
auto Filtered = make_filter_range(E->operands(), [&](const Value *Arg) {
if (Arg == I)
return false;
if (isa<UndefValue>(Arg)) {
HasUndef = true;
return false;
}
return true;
});
// If we are left with no operands, it's undef
if (Filtered.begin() == Filtered.end()) {
DEBUG(dbgs() << "Simplified PHI node " << *I << " to undef"
<< "\n");
E->deallocateOperands(ArgRecycler);
ExpressionAllocator.Deallocate(E);
return createConstantExpression(UndefValue::get(I->getType()));
}
Value *AllSameValue = E->getOperand(0);
// See if all arguments are the same, ignoring undef arguments, because we can
// choose a value that is the same for them.
for (const Value *Arg : E->operands())
if (Arg != AllSameValue && !isa<UndefValue>(Arg)) {
AllSameValue = nullptr;
break;
Value *AllSameValue = *(Filtered.begin());
++Filtered.begin();
// Can't use std::equal here, sadly, because filter.begin moves.
if (llvm::all_of(Filtered, [AllSameValue](const Value *V) {
return V == AllSameValue;
})) {
// In LLVM's non-standard representation of phi nodes, it's possible to have
// phi nodes with cycles (IE dependent on other phis that are .... dependent
// on the original phi node), especially in weird CFG's where some arguments
// are unreachable, or uninitialized along certain paths. This can cause
// infinite loops during evaluation. We work around this by not trying to
// really evaluate them independently, but instead using a variable
// expression to say if one is equivalent to the other.
// We also special case undef, so that if we have an undef, we can't use the
// common value unless it dominates the phi block.
if (HasUndef) {
// Only have to check for instructions
if (Instruction *AllSameInst = dyn_cast<Instruction>(AllSameValue))
if (!DT->dominates(AllSameInst, I))
return E;
}
if (AllSameValue) {
// It's possible to have phi nodes with cycles (IE dependent on
// other phis that are .... dependent on the original phi node),
// especially in weird CFG's where some arguments are unreachable, or
// uninitialized along certain paths.
// This can cause infinite loops during evaluation (even if you disable
// the recursion below, you will simply ping-pong between congruence
// classes). If a phi node symbolically evaluates to another phi node,
// just leave it alone. If they are really the same, we will still
// eliminate them in favor of each other.
if (isa<PHINode>(AllSameValue))
return E;
NumGVNPhisAllSame++;
DEBUG(dbgs() << "Simplified PHI node " << *I << " to " << *AllSameValue
<< "\n");
@ -1867,7 +1881,6 @@ private:
SmallVector<std::pair<int, int>, 8> DFSStack;
};
}
bool NewGVN::eliminateInstructions(Function &F) {
// This is a non-standard eliminator. The normal way to eliminate is
// to walk the dominator tree in order, keeping track of available
@ -1984,9 +1997,13 @@ bool NewGVN::eliminateInstructions(Function &F) {
Value *Member = C.Val;
Use *MemberUse = C.U;
// We ignore void things because we can't get a value from them.
if (Member && Member->getType()->isVoidTy())
continue;
if (Member) {
// We ignore void things because we can't get a value from them.
// FIXME: We could actually use this to kill dead stores that are
// dominated by equivalent earlier stores.
if (Member->getType()->isVoidTy())
continue;
}
if (EliminationStack.empty()) {
DEBUG(dbgs() << "Elimination Stack is empty\n");
@ -1995,8 +2012,6 @@ bool NewGVN::eliminateInstructions(Function &F) {
<< EliminationStack.dfs_back().first << ","
<< EliminationStack.dfs_back().second << ")\n");
}
if (Member && isa<Constant>(Member))
assert(isa<Constant>(CC->RepLeader));
DEBUG(dbgs() << "Current DFS numbers are (" << MemberDFSIn << ","
<< MemberDFSOut << ")\n");
@ -2037,11 +2052,8 @@ bool NewGVN::eliminateInstructions(Function &F) {
continue;
Value *Result = EliminationStack.back();
// Don't replace our existing users with ourselves, and don't replace
// phi node arguments with the result of the same phi node.
// IE tmp = phi(tmp11, undef); tmp11 = foo -> tmp = phi(tmp, undef)
if (MemberUse->get() == Result ||
(isa<PHINode>(Result) && MemberUse->getUser() == Result))
// Don't replace our existing users with ourselves.
if (MemberUse->get() == Result)
continue;
DEBUG(dbgs() << "Found replacement " << *Result << " for "

37
test/Transforms/NewGVN/cyclic-phi-handling.ll Normal file
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@ -0,0 +1,37 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -basicaa -newgvn -S | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
define void @foo(i32 %arg, i32 %arg1, i32 (i32, i32)* %arg2) {
; CHECK-LABEL: @foo(
; CHECK-NEXT: bb:
; CHECK-NEXT: br label %bb3
; CHECK: bb3:
; CHECK-NEXT: [[TMP:%.*]] = phi i32 [ %arg1, %bb ], [ [[TMP:%.*]]4, %bb7 ]
; CHECK-NEXT: [[TMP4:%.*]] = phi i32 [ %arg, %bb ], [ [[TMP]], %bb7 ]
; CHECK-NEXT: [[TMP5:%.*]] = call i32 %arg2(i32 [[TMP4]], i32 [[TMP]])
; CHECK-NEXT: [[TMP6:%.*]] = icmp ne i32 [[TMP5]], 0
; CHECK-NEXT: br i1 [[TMP6]], label %bb7, label %bb8
; CHECK: bb7:
; CHECK-NEXT: br label %bb3
; CHECK: bb8:
; CHECK-NEXT: ret void
;
bb:
br label %bb3
;; While non-standard, llvm allows mutually dependent phi nodes
;; Ensure we do not infinite loop trying to process them
bb3: ; preds = %bb7, %bb
%tmp = phi i32 [ %arg1, %bb ], [ %tmp4, %bb7 ]
%tmp4 = phi i32 [ %arg, %bb ], [ %tmp, %bb7 ]
%tmp5 = call i32 %arg2(i32 %tmp4, i32 %tmp)
%tmp6 = icmp ne i32 %tmp5, 0
br i1 %tmp6, label %bb7, label %bb8
bb7: ; preds = %bb3
br label %bb3
bb8: ; preds = %bb3
ret void
}

136
test/Transforms/NewGVN/pr31501.ll Normal file
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@ -0,0 +1,136 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -basicaa -newgvn -S | FileCheck %s
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
%struct.foo = type { %struct.wombat.28*, %struct.zot, %struct.wombat.28* }
%struct.zot = type { i64 }
%struct.barney = type <{ %struct.wombat.28*, %struct.wibble, %struct.snork, %struct.quux.4, %struct.snork.10, %struct.ham.16*, %struct.wobble.23*, i32, i8, i8, [2 x i8] }>
%struct.wibble = type { %struct.pluto, %struct.bar }
%struct.pluto = type { %struct.quux }
%struct.quux = type { %struct.eggs }
%struct.eggs = type { %struct.zot.0, %struct.widget }
%struct.zot.0 = type { i8*, i8*, i8* }
%struct.widget = type { %struct.barney.1 }
%struct.barney.1 = type { [8 x i8] }
%struct.bar = type { [3 x %struct.widget] }
%struct.snork = type <{ %struct.wobble, %struct.bar.3, [7 x i8] }>
%struct.wobble = type { %struct.wombat }
%struct.wombat = type { %struct.zot.2 }
%struct.zot.2 = type { %struct.zot.0, %struct.ham }
%struct.ham = type { %struct.barney.1 }
%struct.bar.3 = type { i8 }
%struct.quux.4 = type <{ %struct.quux.5, %struct.snork.9, [7 x i8] }>
%struct.quux.5 = type { %struct.widget.6 }
%struct.widget.6 = type { %struct.spam }
%struct.spam = type { %struct.zot.0, %struct.ham.7 }
%struct.ham.7 = type { %struct.barney.8 }
%struct.barney.8 = type { [24 x i8] }
%struct.snork.9 = type { i8 }
%struct.snork.10 = type <{ %struct.foo.11, %struct.spam.15, [7 x i8] }>
%struct.foo.11 = type { %struct.snork.12 }
%struct.snork.12 = type { %struct.wombat.13 }
%struct.wombat.13 = type { %struct.zot.0, %struct.wibble.14 }
%struct.wibble.14 = type { %struct.barney.8 }
%struct.spam.15 = type { i8 }
%struct.ham.16 = type { %struct.pluto.17, %struct.pluto.17 }
%struct.pluto.17 = type { %struct.bar.18 }
%struct.bar.18 = type { %struct.baz*, %struct.zot.20, %struct.barney.22 }
%struct.baz = type { %struct.wibble.19* }
%struct.wibble.19 = type <{ %struct.baz, %struct.wibble.19*, %struct.baz*, i8, [7 x i8] }>
%struct.zot.20 = type { %struct.ham.21 }
%struct.ham.21 = type { %struct.baz }
%struct.barney.22 = type { %struct.blam }
%struct.blam = type { i64 }
%struct.wobble.23 = type { %struct.spam.24, %struct.barney* }
%struct.spam.24 = type { %struct.bar.25, %struct.zot.26* }
%struct.bar.25 = type <{ i32 (...)**, i8, i8 }>
%struct.zot.26 = type { i32 (...)**, i32, %struct.widget.27* }
%struct.widget.27 = type { %struct.zot.26, %struct.zot.26* }
%struct.wombat.28 = type <{ i32 (...)**, i8, i8, [6 x i8] }>
; Function Attrs: norecurse nounwind ssp uwtable
define weak_odr hidden %struct.foo* @quux(%struct.barney* %arg, %struct.wombat.28* %arg1) local_unnamed_addr #0 align 2 {
; CHECK-LABEL: @quux(
; CHECK-NEXT: bb:
; CHECK-NEXT: [[TMP:%.*]] = getelementptr inbounds %struct.barney, %struct.barney* %arg, i64 0, i32 3, i32 0, i32 0, i32 0
; CHECK-NEXT: [[TMP2:%.*]] = bitcast %struct.spam* [[TMP]] to %struct.foo**
; CHECK-NEXT: [[TMP3:%.*]] = load %struct.foo*, %struct.foo** [[TMP2]], align 8, !tbaa !2
; CHECK-NEXT: [[TMP4:%.*]] = getelementptr inbounds %struct.barney, %struct.barney* %arg, i64 0, i32 3, i32 0, i32 0, i32 0, i32 0, i32 1
; CHECK-NEXT: [[TMP5:%.*]] = bitcast i8** [[TMP4]] to %struct.foo**
; CHECK-NEXT: [[TMP6:%.*]] = load %struct.foo*, %struct.foo** [[TMP5]], align 8, !tbaa !7
; CHECK-NEXT: [[TMP7:%.*]] = icmp eq %struct.foo* [[TMP3]], [[TMP6]]
; CHECK-NEXT: br i1 [[TMP7]], label %bb21, label %bb8
; CHECK: bb8:
; CHECK-NEXT: br label %bb11
; CHECK: bb9:
; CHECK-NEXT: [[TMP10:%.*]] = icmp eq %struct.foo* [[TMP18:%.*]], [[TMP6]]
; CHECK-NEXT: br i1 [[TMP10]], label %bb19, label %bb11
; CHECK: bb11:
; CHECK-NEXT: [[TMP12:%.*]] = phi %struct.foo* [ [[TMP17:%.*]], %bb9 ], [ undef, %bb8 ]
; CHECK-NEXT: [[TMP13:%.*]] = phi %struct.foo* [ [[TMP18]], %bb9 ], [ [[TMP3]], %bb8 ]
; CHECK-NEXT: [[TMP14:%.*]] = getelementptr inbounds %struct.foo, %struct.foo* [[TMP13]], i64 0, i32 0
; CHECK-NEXT: [[TMP15:%.*]] = load %struct.wombat.28*, %struct.wombat.28** [[TMP14]], align 8, !tbaa !8
; CHECK-NEXT: [[TMP16:%.*]] = icmp eq %struct.wombat.28* [[TMP15]], %arg1
; CHECK-NEXT: [[TMP17]] = select i1 [[TMP16]], %struct.foo* [[TMP13]], %struct.foo* [[TMP12]]
; CHECK-NEXT: [[TMP18]] = getelementptr inbounds %struct.foo, %struct.foo* [[TMP13]], i64 1
; CHECK-NEXT: br i1 [[TMP16]], label %bb19, label %bb9
; CHECK: bb19:
; CHECK-NEXT: [[TMP20:%.*]] = phi %struct.foo* [ null, %bb9 ], [ [[TMP17]], %bb11 ]
; CHECK-NEXT: br label %bb21
; CHECK: bb21:
; CHECK-NEXT: [[TMP22:%.*]] = phi %struct.foo* [ null, %bb ], [ [[TMP20]], %bb19 ]
; CHECK-NEXT: ret %struct.foo* [[TMP22]]
;
bb:
%tmp = getelementptr inbounds %struct.barney, %struct.barney* %arg, i64 0, i32 3, i32 0, i32 0, i32 0
%tmp2 = bitcast %struct.spam* %tmp to %struct.foo**
%tmp3 = load %struct.foo*, %struct.foo** %tmp2, align 8, !tbaa !2
%tmp4 = getelementptr inbounds %struct.barney, %struct.barney* %arg, i64 0, i32 3, i32 0, i32 0, i32 0, i32 0, i32 1
%tmp5 = bitcast i8** %tmp4 to %struct.foo**
%tmp6 = load %struct.foo*, %struct.foo** %tmp5, align 8, !tbaa !7
%tmp7 = icmp eq %struct.foo* %tmp3, %tmp6
br i1 %tmp7, label %bb21, label %bb8
bb8: ; preds = %bb
br label %bb11
bb9: ; preds = %bb11
%tmp10 = icmp eq %struct.foo* %tmp18, %tmp6
br i1 %tmp10, label %bb19, label %bb11
bb11: ; preds = %bb9, %bb8
%tmp12 = phi %struct.foo* [ %tmp17, %bb9 ], [ undef, %bb8 ]
%tmp13 = phi %struct.foo* [ %tmp18, %bb9 ], [ %tmp3, %bb8 ]
%tmp14 = getelementptr inbounds %struct.foo, %struct.foo* %tmp13, i64 0, i32 0
%tmp15 = load %struct.wombat.28*, %struct.wombat.28** %tmp14, align 8, !tbaa !8
%tmp16 = icmp eq %struct.wombat.28* %tmp15, %arg1
%tmp17 = select i1 %tmp16, %struct.foo* %tmp13, %struct.foo* %tmp12
%tmp18 = getelementptr inbounds %struct.foo, %struct.foo* %tmp13, i64 1
br i1 %tmp16, label %bb19, label %bb9
bb19: ; preds = %bb11, %bb9
%tmp20 = phi %struct.foo* [ null, %bb9 ], [ %tmp17, %bb11 ]
br label %bb21
bb21: ; preds = %bb19, %bb
%tmp22 = phi %struct.foo* [ null, %bb ], [ %tmp20, %bb19 ]
ret %struct.foo* %tmp22
}
attributes #0 = { norecurse nounwind ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 1, !"PIC Level", i32 2}
!1 = !{!"clang version 4.0.0 (http://llvm.org/git/clang.git b63fa9e2bb8aac0a80c3e3467991c6b1a4b01e6a) (llvm/trunk 290779)"}
!2 = !{!3, !4, i64 0}
!3 = !{!"_ZTSN4llvm15SmallVectorBaseE", !4, i64 0, !4, i64 8, !4, i64 16}
!4 = !{!"any pointer", !5, i64 0}
!5 = !{!"omnipotent char", !6, i64 0}
!6 = !{!"Simple C++ TBAA"}
!7 = !{!3, !4, i64 8}
!8 = !{!9, !4, i64 0}
!9 = !{!"_ZTSN4llvm9RecordValE", !4, i64 0, !10, i64 8, !4, i64 16}
!10 = !{!"_ZTSN4llvm14PointerIntPairIPNS_5RecTyELj1EbNS_21PointerLikeTypeTraitsIS2_EENS_18PointerIntPairInfoIS2_Lj1ES4_EEEE", !11, i64 0}
!11 = !{!"long", !5, i64 0}