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Code Issues Releases Activity

llvm: Revert "[HardwareLoops] Change order of SCEV expression construction for InitLoopCount."

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Reverts llvm commit 42eaf4fe0adef3344adfd9fbccd49f325cb549ef, pointed
from bisect as source of regression that causes liblzma to compress/
uncompress incorrectly. It's know to affect powerpc64 BE only.

The patch unbreaks FreeBSD powerpc64 installation media, since
bsdinstall can't uncompress the *.txz produced by FreeBSD CI. It's
probably miscompiling other software bas well.

Upstream PR: https://bugs.llvm.org/show_bug.cgi?id=51714

Reviewed by:	dim
MFC after:	2 days
Sponsored by:	Instituto de Pesquisas Eldorado (eldorado.org.br)
Differential Revision:	https://reviews.freebsd.org/D31804
This commit is contained in:
Alfredo Dal'Ava Junior 2021-09-02 14:54:31 -03:00
parent bd452dcbed
commit f21fcae487
3 changed files with 18 additions and 14 deletions
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1
contrib/llvm-project/llvm/include/llvm/Analysis/TargetTransformInfo.h
View File

@ -94,6 +94,7 @@ struct HardwareLoopInfo {
Loop *L = nullptr;
BasicBlock *ExitBlock = nullptr;
BranchInst *ExitBranch = nullptr;
const SCEV *ExitCount = nullptr;
const SCEV *TripCount = nullptr;
IntegerType *CountType = nullptr;
Value *LoopDecrement = nullptr; // Decrement the loop counter by this

5
contrib/llvm-project/llvm/lib/Analysis/TargetTransformInfo.cpp
View File

@ -217,10 +217,7 @@ bool HardwareLoopInfo::isHardwareLoopCandidate(ScalarEvolution &SE,
// Note that this block may not be the loop latch block, even if the loop
// has a latch block.
ExitBlock = BB;
TripCount = SE.getAddExpr(EC, SE.getOne(EC->getType()));
if (!EC->getType()->isPointerTy() && EC->getType() != CountType)
TripCount = SE.getZeroExtendExpr(TripCount, CountType);
ExitCount = EC;
break;
}

26
contrib/llvm-project/llvm/lib/CodeGen/HardwareLoops.cpp
View File

@ -187,7 +187,7 @@ namespace {
const DataLayout &DL,
OptimizationRemarkEmitter *ORE) :
SE(SE), DL(DL), ORE(ORE), L(Info.L), M(L->getHeader()->getModule()),
TripCount(Info.TripCount),
ExitCount(Info.ExitCount),
CountType(Info.CountType),
ExitBranch(Info.ExitBranch),
LoopDecrement(Info.LoopDecrement),
@ -202,7 +202,7 @@ namespace {
OptimizationRemarkEmitter *ORE = nullptr;
Loop *L = nullptr;
Module *M = nullptr;
const SCEV *TripCount = nullptr;
const SCEV *ExitCount = nullptr;
Type *CountType = nullptr;
BranchInst *ExitBranch = nullptr;
Value *LoopDecrement = nullptr;
@ -298,7 +298,7 @@ bool HardwareLoops::TryConvertLoop(HardwareLoopInfo &HWLoopInfo) {
}
assert(
(HWLoopInfo.ExitBlock && HWLoopInfo.ExitBranch && HWLoopInfo.TripCount) &&
(HWLoopInfo.ExitBlock && HWLoopInfo.ExitBranch && HWLoopInfo.ExitCount) &&
"Hardware Loop must have set exit info.");
BasicBlock *Preheader = L->getLoopPreheader();
@ -384,12 +384,18 @@ Value *HardwareLoop::InitLoopCount() {
SCEVExpander SCEVE(SE, DL, "loopcnt");
if (!ExitCount->getType()->isPointerTy() &&
ExitCount->getType() != CountType)
ExitCount = SE.getZeroExtendExpr(ExitCount, CountType);
ExitCount = SE.getAddExpr(ExitCount, SE.getOne(CountType));
// If we're trying to use the 'test and set' form of the intrinsic, we need
// to replace a conditional branch that is controlling entry to the loop. It
// is likely (guaranteed?) that the preheader has an unconditional branch to
// the loop header, so also check if it has a single predecessor.
if (SE.isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, TripCount,
SE.getZero(TripCount->getType()))) {
if (SE.isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, ExitCount,
SE.getZero(ExitCount->getType()))) {
LLVM_DEBUG(dbgs() << " - Attempting to use test.set counter.\n");
UseLoopGuard |= ForceGuardLoopEntry;
} else
@ -401,19 +407,19 @@ Value *HardwareLoop::InitLoopCount() {
BasicBlock *Predecessor = BB->getSinglePredecessor();
// If it's not safe to create a while loop then don't force it and create a
// do-while loop instead
if (!isSafeToExpandAt(TripCount, Predecessor->getTerminator(), SE))
if (!isSafeToExpandAt(ExitCount, Predecessor->getTerminator(), SE))
UseLoopGuard = false;
else
BB = Predecessor;
}
if (!isSafeToExpandAt(TripCount, BB->getTerminator(), SE)) {
LLVM_DEBUG(dbgs() << "- Bailing, unsafe to expand TripCount "
<< *TripCount << "\n");
if (!isSafeToExpandAt(ExitCount, BB->getTerminator(), SE)) {
LLVM_DEBUG(dbgs() << "- Bailing, unsafe to expand ExitCount "
<< *ExitCount << "\n");
return nullptr;
}
Value *Count = SCEVE.expandCodeFor(TripCount, CountType,
Value *Count = SCEVE.expandCodeFor(ExitCount, CountType,
BB->getTerminator());
// FIXME: We've expanded Count where we hope to insert the counter setting