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Revert commit from upstream llvm trunk (by Hans Wennborg):

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Re-commit r357452 (take 3): "SimplifyCFG
  SinkCommonCodeFromPredecessors: Also sink function calls without used
  results (PR41259)"

  Third time's the charm.

  This was reverted in r363220 due to being suspected of an internal
  benchmark regression and a test failure, none of which turned out to
  be caused by this.

As reported in https://bugs.llvm.org/show_bug.cgi?id=43269, this causes
UNREACHABLE errors when compiling if_malo_pci.c for arm and aarch64.
This commit is contained in:
Dimitry Andric 2019-09-14 10:55:33 +00:00
parent e89f883a18
commit ceb19815c7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/projects/clang900-import/; revision=352318
1 changed files with 14 additions and 15 deletions
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29
contrib/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
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@ -1428,10 +1428,9 @@ static bool HoistThenElseCodeToIf(BranchInst *BI,
static bool canSinkInstructions(
ArrayRef<Instruction *> Insts,
DenseMap<Instruction *, SmallVector<Value *, 4>> &PHIOperands) {
// Prune out obviously bad instructions to move. Each instruction must have
// exactly zero or one use, and we check later that use is by a single, common
// PHI instruction in the successor.
bool HasUse = !Insts.front()->user_empty();
// Prune out obviously bad instructions to move. Any non-store instruction
// must have exactly one use, and we check later that use is by a single,
// common PHI instruction in the successor.
for (auto *I : Insts) {
// These instructions may change or break semantics if moved.
if (isa<PHINode>(I) || I->isEHPad() || isa<AllocaInst>(I) ||
@ -1445,10 +1444,9 @@ static bool canSinkInstructions(
if (C->isInlineAsm())
return false;
// Each instruction must have zero or one use.
if (HasUse && !I->hasOneUse())
return false;
if (!HasUse && !I->user_empty())
// Everything must have only one use too, apart from stores which
// have no uses.
if (!isa<StoreInst>(I) && !I->hasOneUse())
return false;
}
@ -1457,11 +1455,11 @@ static bool canSinkInstructions(
if (!I->isSameOperationAs(I0))
return false;
// All instructions in Insts are known to be the same opcode. If they have a
// use, check that the only user is a PHI or in the same block as the
// instruction, because if a user is in the same block as an instruction we're
// contemplating sinking, it must already be determined to be sinkable.
if (HasUse) {
// All instructions in Insts are known to be the same opcode. If they aren't
// stores, check the only user of each is a PHI or in the same block as the
// instruction, because if a user is in the same block as an instruction
// we're contemplating sinking, it must already be determined to be sinkable.
if (!isa<StoreInst>(I0)) {
auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
auto *Succ = I0->getParent()->getTerminator()->getSuccessor(0);
if (!all_of(Insts, [&PNUse,&Succ](const Instruction *I) -> bool {
@ -1539,7 +1537,7 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
// it is slightly over-aggressive - it gets confused by commutative instructions
// so double-check it here.
Instruction *I0 = Insts.front();
if (!I0->user_empty()) {
if (!isa<StoreInst>(I0)) {
auto *PNUse = dyn_cast<PHINode>(*I0->user_begin());
if (!all_of(Insts, [&PNUse](const Instruction *I) -> bool {
auto *U = cast<Instruction>(*I->user_begin());
@ -1597,10 +1595,11 @@ static bool sinkLastInstruction(ArrayRef<BasicBlock*> Blocks) {
I0->andIRFlags(I);
}
if (!I0->user_empty()) {
if (!isa<StoreInst>(I0)) {
// canSinkLastInstruction checked that all instructions were used by
// one and only one PHI node. Find that now, RAUW it to our common
// instruction and nuke it.
assert(I0->hasOneUse());
auto *PN = cast<PHINode>(*I0->user_begin());
PN->replaceAllUsesWith(I0);
PN->eraseFromParent();