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[ScheduleDAG] Fix unfolding of SUnits to already existent nodes. 

Summary:
If unfolding an SUnit results in both load or the operation using it which
already exist in the DAG, abort the unfold if they are already scheduled.
If not, make sure we don't add duplicate dependencies.

This fixes PR37916.

Reviewers: davide, eli.friedman, fhahn, bogner

Subscribers: MatzeB, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D48666

llvm-svn: 337409
This commit is contained in:
Nirav Dave 2018-07-18 18:01:03 +00:00
parent 6e13790801
commit a747d3ca60
2 changed files with 74 additions and 18 deletions
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32
llvm/lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
View File

@ -1010,16 +1010,18 @@ SUnit *ScheduleDAGRRList::TryUnfoldSU(SUnit *SU) {
computeLatency(LoadSU);
}
LLVM_DEBUG(dbgs() << "Unfolding SU #" << SU->NodeNum << "\n");
// Now that we are committed to unfolding replace DAG Uses.
for (unsigned i = 0; i != NumVals; ++i)
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), i), SDValue(N, i));
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), OldNumVals - 1),
SDValue(LoadNode, 1));
SUnit *NewSU = CreateNewSUnit(N);
assert(N->getNodeId() == -1 && "Node already inserted!");
bool isNewN = true;
SUnit *NewSU;
// This can only happen when isNewLoad is false.
if (N->getNodeId() != -1) {
NewSU = &SUnits[N->getNodeId()];
// If NewSU has already been scheduled, we need to clone it, but this
// negates the benefit to unfolding so just return SU.
if (NewSU->isScheduled)
return SU;
isNewN = false;
} else {
NewSU = CreateNewSUnit(N);
N->setNodeId(NewSU->NodeNum);
const MCInstrDesc &MCID = TII->get(N->getMachineOpcode());
@ -1034,6 +1036,15 @@ SUnit *ScheduleDAGRRList::TryUnfoldSU(SUnit *SU) {
InitNumRegDefsLeft(NewSU);
computeLatency(NewSU);
}
LLVM_DEBUG(dbgs() << "Unfolding SU #" << SU->NodeNum << "\n");
// Now that we are committed to unfolding replace DAG Uses.
for (unsigned i = 0; i != NumVals; ++i)
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), i), SDValue(N, i));
DAG->ReplaceAllUsesOfValueWith(SDValue(SU->getNode(), OldNumVals - 1),
SDValue(LoadNode, 1));
// Record all the edges to and from the old SU, by category.
SmallVector<SDep, 4> ChainPreds;
@ -1100,6 +1111,7 @@ SUnit *ScheduleDAGRRList::TryUnfoldSU(SUnit *SU) {
if (isNewLoad)
AvailableQueue->addNode(LoadSU);
if (isNewN)
AvailableQueue->addNode(NewSU);
++NumUnfolds;

44
llvm/test/CodeGen/X86/pr37916.ll Normal file
View File

@ -0,0 +1,44 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc -mtriple=i386-unknown-linux-gnu %s -o - | FileCheck %s
@f = external local_unnamed_addr global i64*, align 4
@a = external global i64, align 8
define void @fn1() local_unnamed_addr {
; CHECK-LABEL: fn1:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: .p2align 4, 0x90
; CHECK-NEXT: .LBB0_1: # %if.end
; CHECK-NEXT: # =>This Inner Loop Header: Depth=1
; CHECK-NEXT: movl a+4, %eax
; CHECK-NEXT: orl a, %eax
; CHECK-NEXT: movl $a, f
; CHECK-NEXT: je .LBB0_3
; CHECK-NEXT: # %bb.2: # %if.end
; CHECK-NEXT: # in Loop: Header=BB0_1 Depth=1
; CHECK-NEXT: jne .LBB0_1
; CHECK-NEXT: .LBB0_3: # %cond.false
entry:
br label %if.end
if.end: ; preds = %cond.end, %entry
br label %if.then7
if.then7: ; preds = %if.end
store i64* @a, i64** @f, align 4
%0 = load i64*, i64** @f, align 4
%1 = load i64, i64* %0, align 4
%tobool12 = icmp ne i64 %1, 0
%2 = load i64, i64* @a, align 8
%tobool13 = icmp ne i64 %2, 0
%3 = and i1 %tobool12, %tobool13
%tobool14.demorgan = and i1 %tobool12, %tobool13
br i1 %tobool14.demorgan, label %cond.end, label %cond.false
cond.false: ; preds = %if.then7
unreachable
cond.end: ; preds = %if.then7
%conv17 = sext i1 %3 to i8
br label %if.end
}