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Fixes PR8823: add-with-overflow-128.ll

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In the bottom-up selection DAG scheduling, handle two-address
instructions that read/write unspillable registers. Treat
the entire chain of two-address nodes as a single live range.

llvm-svn: 122472
This commit is contained in:
Andrew Trick 2010-12-23 03:15:51 +00:00
parent eb2ae28352
commit cc701bcfdc
2 changed files with 34 additions and 15 deletions
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45
lib/CodeGen/SelectionDAG/ScheduleDAGRRList.cpp
View File

@ -247,6 +247,23 @@ void ScheduleDAGRRList::ReleasePred(SUnit *SU, const SDep *PredEdge) {
}
}
/// Call ReleasePred for each predecessor, then update register live def/gen.
/// Always update LiveRegDefs for a register dependence even if the current SU
/// also defines the register. This effectively create one large live range
/// across a sequence of two-address node. This is important because the
/// entire chain must be scheduled together. Example:
///
/// flags = (3) add
/// flags = (2) addc flags
/// flags = (1) addc flags
///
/// results in
///
/// LiveRegDefs[flags] = 3
/// LiveRegCycles[flags] = 1
///
/// If (2) addc is unscheduled, then (1) addc must also be unscheduled to avoid
/// interference on flags.
void ScheduleDAGRRList::ReleasePredecessors(SUnit *SU, unsigned CurCycle) {
// Bottom up: release predecessors
for (SUnit::pred_iterator I = SU->Preds.begin(), E = SU->Preds.end();
@ -257,9 +274,12 @@ void ScheduleDAGRRList::ReleasePredecessors(SUnit *SU, unsigned CurCycle) {
// expensive to copy the register. Make sure nothing that can
// clobber the register is scheduled between the predecessor and
// this node.
if (!LiveRegDefs[I->getReg()]) {
SUnit *&RegDef = LiveRegDefs[I->getReg()];
assert((!RegDef || RegDef == SU || RegDef == I->getSUnit()) &&
"interference on register dependence");
RegDef = I->getSUnit();
if (!LiveRegCycles[I->getReg()]) {
++NumLiveRegs;
LiveRegDefs[I->getReg()] = I->getSUnit();
LiveRegCycles[I->getReg()] = CurCycle;
}
}
@ -284,20 +304,19 @@ void ScheduleDAGRRList::ScheduleNodeBottomUp(SUnit *SU, unsigned CurCycle) {
AvailableQueue->ScheduledNode(SU);
// Update liveness of predecessors before successors to avoid treating a
// two-address node as a live range def.
ReleasePredecessors(SU, CurCycle);
// Release all the implicit physical register defs that are live.
for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
if (I->isAssignedRegDep()) {
if (LiveRegCycles[I->getReg()] == I->getSUnit()->getHeight()) {
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
assert(LiveRegDefs[I->getReg()] == SU &&
"Physical register dependency violated?");
--NumLiveRegs;
LiveRegDefs[I->getReg()] = NULL;
LiveRegCycles[I->getReg()] = 0;
}
// LiveRegDegs[I->getReg()] != SU when SU is a two-address node.
if (I->isAssignedRegDep() && LiveRegDefs[I->getReg()] == SU) {
assert(NumLiveRegs > 0 && "NumLiveRegs is already zero!");
--NumLiveRegs;
LiveRegDefs[I->getReg()] = NULL;
LiveRegCycles[I->getReg()] = 0;
}
}
@ -341,8 +360,10 @@ void ScheduleDAGRRList::UnscheduleNodeBottomUp(SUnit *SU) {
for (SUnit::succ_iterator I = SU->Succs.begin(), E = SU->Succs.end();
I != E; ++I) {
if (I->isAssignedRegDep()) {
// This becomes the nearest def. Note that an earlier def may still be
// pending if this is a two-address node.
LiveRegDefs[I->getReg()] = SU;
if (!LiveRegDefs[I->getReg()]) {
LiveRegDefs[I->getReg()] = SU;
++NumLiveRegs;
}
if (I->getSUnit()->getHeight() < LiveRegCycles[I->getReg()])

4
test/CodeGen/Generic/add-with-overflow-128.ll
View File

@ -1,6 +1,4 @@
; RUN: true
; FIXME: TEmporarily disabled: PR8823
; llc < %s
; RUN: llc < %s
@ok = internal constant [4 x i8] c"%d\0A\00"
@no = internal constant [4 x i8] c"no\0A\00"