Implement bottom-up fast-isel. This has the advantage of not requiring
a separate DCE pass over MachineInstrs.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@107804 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index bea65b2..8918516 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -680,60 +680,55 @@
BasicBlock::const_iterator const Begin = LLVMBB->getFirstNonPHI();
BasicBlock::const_iterator const End = LLVMBB->end();
- BasicBlock::const_iterator BI = Begin;
+ BasicBlock::const_iterator BI = End;
- // Lower any arguments needed in this block if this is the entry block.
- if (LLVMBB == &Fn.getEntryBlock())
- LowerArguments(LLVMBB);
-
- // Setup an EH landing-pad block.
- if (FuncInfo->MBB->isLandingPad())
- PrepareEHLandingPad();
-
// Before doing SelectionDAG ISel, see if FastISel has been requested.
if (FastIS) {
- // Emit code for any incoming arguments. This must happen before
- // beginning FastISel on the entry block.
- if (LLVMBB == &Fn.getEntryBlock()) {
- CurDAG->setRoot(SDB->getControlRoot());
- SDB->clear();
- CodeGenAndEmitDAG();
- }
FastIS->startNewBlock();
+
// Do FastISel on as many instructions as possible.
- for (; BI != End; ++BI) {
-#if 0
- // Defer instructions with no side effects; they'll be emitted
- // on-demand later.
- if (BI->isSafeToSpeculativelyExecute() &&
- !FuncInfo->isExportedInst(BI))
+ for (; BI != Begin; --BI) {
+ const Instruction *Inst = llvm::prior(BI);
+
+ // If we no longer require this instruction, skip it.
+ if (!Inst->mayWriteToMemory() &&
+ !isa<TerminatorInst>(Inst) &&
+ !isa<DbgInfoIntrinsic>(Inst) &&
+ !FuncInfo->isExportedInst(Inst))
continue;
-#endif
+
+ // Bottom-up: reset the insert pos at the top, after any local-value
+ // instructions.
+ MachineBasicBlock::iterator LVIP = FastIS->getLastLocalValue();
+ if (LVIP != FuncInfo->MBB->end())
+ FuncInfo->InsertPt = next(LVIP);
+ else
+ FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();
// Try to select the instruction with FastISel.
- if (FastIS->SelectInstruction(BI))
+ if (FastIS->SelectInstruction(Inst))
continue;
// Then handle certain instructions as single-LLVM-Instruction blocks.
- if (isa<CallInst>(BI)) {
+ if (isa<CallInst>(Inst)) {
++NumFastIselFailures;
if (EnableFastISelVerbose || EnableFastISelAbort) {
dbgs() << "FastISel missed call: ";
- BI->dump();
+ Inst->dump();
}
- if (!BI->getType()->isVoidTy() && !BI->use_empty()) {
- unsigned &R = FuncInfo->ValueMap[BI];
+ if (!Inst->getType()->isVoidTy() && !Inst->use_empty()) {
+ unsigned &R = FuncInfo->ValueMap[Inst];
if (!R)
- R = FuncInfo->CreateRegs(BI->getType());
+ R = FuncInfo->CreateRegs(Inst->getType());
}
bool HadTailCall = false;
- SelectBasicBlock(BI, llvm::next(BI), HadTailCall);
+ SelectBasicBlock(Inst, BI, HadTailCall);
// If the call was emitted as a tail call, we're done with the block.
if (HadTailCall) {
- BI = End;
+ --BI;
break;
}
@@ -746,7 +741,7 @@
++NumFastIselFailures;
if (EnableFastISelVerbose || EnableFastISelAbort) {
dbgs() << "FastISel miss: ";
- BI->dump();
+ Inst->dump();
}
if (EnableFastISelAbort)
// The "fast" selector couldn't handle something and bailed.
@@ -757,13 +752,21 @@
}
}
+ FuncInfo->InsertPt = FuncInfo->MBB->getFirstNonPHI();
+
+ // Setup an EH landing-pad block.
+ if (FuncInfo->MBB->isLandingPad())
+ PrepareEHLandingPad();
+
+ // Lower any arguments needed in this block if this is the entry block.
+ if (LLVMBB == &Fn.getEntryBlock())
+ LowerArguments(LLVMBB);
+
// Run SelectionDAG instruction selection on the remainder of the block
// not handled by FastISel. If FastISel is not run, this is the entire
// block.
- if (BI != End) {
- bool HadTailCall;
- SelectBasicBlock(BI, End, HadTailCall);
- }
+ bool HadTailCall;
+ SelectBasicBlock(Begin, BI, HadTailCall);
FinishBasicBlock();
FuncInfo->PHINodesToUpdate.clear();
@@ -963,7 +966,8 @@
for (unsigned i = 0, e = Succs.size(); i != e; ++i) {
FuncInfo->MBB = Succs[i];
FuncInfo->InsertPt = FuncInfo->MBB->end();
- // BB may have been removed from the CFG if a branch was constant folded.
+ // FuncInfo->MBB may have been removed from the CFG if a branch was
+ // constant folded.
if (ThisBB->isSuccessor(FuncInfo->MBB)) {
for (MachineBasicBlock::iterator Phi = FuncInfo->MBB->begin();
Phi != FuncInfo->MBB->end() && Phi->isPHI();