[GlobalISel] Preserve IR block layout.
It makes the output function layout more predictable; the layout has
an effect on performance, we don't want it to be at the mercy of the
translator's visitation order and such.
The predictable output is also easier to digest.
getOrCreateBB isn't appropriately named anymore, as it never needs to
create anything. Rename it and extract the MBB creation logic out of it.
A couple tests were sensitive to the order. Update them.
llvm-svn: 297868
diff --git a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
index cf0c660..2bcb555 100644
--- a/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp
@@ -140,15 +140,9 @@
return Alignment ? Alignment : DL->getABITypeAlignment(ValTy);
}
-MachineBasicBlock &IRTranslator::getOrCreateBB(const BasicBlock &BB) {
+MachineBasicBlock &IRTranslator::getMBB(const BasicBlock &BB) {
MachineBasicBlock *&MBB = BBToMBB[&BB];
- if (!MBB) {
- MBB = MF->CreateMachineBasicBlock(&BB);
- MF->push_back(MBB);
-
- if (BB.hasAddressTaken())
- MBB->setHasAddressTaken();
- }
+ assert(MBB && "BasicBlock was not encountered before");
return *MBB;
}
@@ -221,18 +215,18 @@
// We want a G_BRCOND to the true BB followed by an unconditional branch.
unsigned Tst = getOrCreateVReg(*BrInst.getCondition());
const BasicBlock &TrueTgt = *cast<BasicBlock>(BrInst.getSuccessor(Succ++));
- MachineBasicBlock &TrueBB = getOrCreateBB(TrueTgt);
+ MachineBasicBlock &TrueBB = getMBB(TrueTgt);
MIRBuilder.buildBrCond(Tst, TrueBB);
}
const BasicBlock &BrTgt = *cast<BasicBlock>(BrInst.getSuccessor(Succ));
- MachineBasicBlock &TgtBB = getOrCreateBB(BrTgt);
+ MachineBasicBlock &TgtBB = getMBB(BrTgt);
MIRBuilder.buildBr(TgtBB);
// Link successors.
MachineBasicBlock &CurBB = MIRBuilder.getMBB();
for (const BasicBlock *Succ : BrInst.successors())
- CurBB.addSuccessor(&getOrCreateBB(*Succ));
+ CurBB.addSuccessor(&getMBB(*Succ));
return true;
}
@@ -256,7 +250,7 @@
MIRBuilder.buildICmp(CmpInst::ICMP_EQ, Tst, CaseValueReg, SwCondValue);
MachineBasicBlock &CurMBB = MIRBuilder.getMBB();
const BasicBlock *TrueBB = CaseIt.getCaseSuccessor();
- MachineBasicBlock &TrueMBB = getOrCreateBB(*TrueBB);
+ MachineBasicBlock &TrueMBB = getMBB(*TrueBB);
MIRBuilder.buildBrCond(Tst, TrueMBB);
CurMBB.addSuccessor(&TrueMBB);
@@ -272,7 +266,7 @@
}
// handle default case
const BasicBlock *DefaultBB = SwInst.getDefaultDest();
- MachineBasicBlock &DefaultMBB = getOrCreateBB(*DefaultBB);
+ MachineBasicBlock &DefaultMBB = getMBB(*DefaultBB);
MIRBuilder.buildBr(DefaultMBB);
MachineBasicBlock &CurMBB = MIRBuilder.getMBB();
CurMBB.addSuccessor(&DefaultMBB);
@@ -291,7 +285,7 @@
// Link successors.
MachineBasicBlock &CurBB = MIRBuilder.getMBB();
for (const BasicBlock *Succ : BrInst.successors())
- CurBB.addSuccessor(&getOrCreateBB(*Succ));
+ CurBB.addSuccessor(&getMBB(*Succ));
return true;
}
@@ -823,8 +817,8 @@
MIRBuilder.buildInstr(TargetOpcode::EH_LABEL).addSym(EndSymbol);
// FIXME: track probabilities.
- MachineBasicBlock &EHPadMBB = getOrCreateBB(*EHPadBB),
- &ReturnMBB = getOrCreateBB(*ReturnBB);
+ MachineBasicBlock &EHPadMBB = getMBB(*EHPadBB),
+ &ReturnMBB = getMBB(*ReturnBB);
MF->addInvoke(&EHPadMBB, BeginSymbol, EndSymbol);
MIRBuilder.getMBB().addSuccessor(&ReturnMBB);
MIRBuilder.getMBB().addSuccessor(&EHPadMBB);
@@ -1128,13 +1122,25 @@
// Release the per-function state when we return, whether we succeeded or not.
auto FinalizeOnReturn = make_scope_exit([this]() { finalizeFunction(); });
- // Setup a separate basic-block for the arguments and constants, falling
- // through to the IR-level Function's entry block.
+ // Setup a separate basic-block for the arguments and constants
MachineBasicBlock *EntryBB = MF->CreateMachineBasicBlock();
MF->push_back(EntryBB);
- EntryBB->addSuccessor(&getOrCreateBB(F.front()));
EntryBuilder.setMBB(*EntryBB);
+ // Create all blocks, in IR order, to preserve the layout.
+ for (const BasicBlock &BB: F) {
+ auto *&MBB = BBToMBB[&BB];
+
+ MBB = MF->CreateMachineBasicBlock(&BB);
+ MF->push_back(MBB);
+
+ if (BB.hasAddressTaken())
+ MBB->setHasAddressTaken();
+ }
+
+ // Make our arguments/constants entry block fallthrough to the IR entry block.
+ EntryBB->addSuccessor(&getMBB(F.front()));
+
// Lower the actual args into this basic block.
SmallVector<unsigned, 8> VRegArgs;
for (const Argument &Arg: F.args())
@@ -1150,7 +1156,7 @@
// And translate the function!
for (const BasicBlock &BB: F) {
- MachineBasicBlock &MBB = getOrCreateBB(BB);
+ MachineBasicBlock &MBB = getMBB(BB);
// Set the insertion point of all the following translations to
// the end of this basic block.
CurBuilder.setMBB(MBB);