Add some comments suggested in code review.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159800 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/EarlyIfConversion.cpp b/lib/CodeGen/EarlyIfConversion.cpp
index f575b24..effddfb 100644
--- a/lib/CodeGen/EarlyIfConversion.cpp
+++ b/lib/CodeGen/EarlyIfConversion.cpp
@@ -167,6 +167,9 @@
}
unsigned InstrCount = 0;
+
+ // Check all instructions, except the terminators. It is assumed that
+ // terminators never have side effects or define any used register values.
for (MachineBasicBlock::iterator I = MBB->begin(),
E = MBB->getFirstTerminator(); I != E; ++I) {
if (I->isDebugValue())
@@ -569,11 +572,15 @@
bool Changed = false;
IfConv.runOnMachineFunction(MF);
+ // Initially visit blocks in layout order. The tryConvertIf() function may
+ // erase blocks, but never the head block passed as MFI.
for (MachineFunction::iterator MFI = MF.begin(), MFE = MF.end(); MFI != MFE;
++MFI)
if (tryConvertIf(MFI))
Changed = true;
+ // Revisit blocks identified by tryConvertIf() as candidates for nested
+ // if-conversion.
DEBUG(dbgs() << "Revisiting " << WorkList.size() << " blocks.\n");
while (!WorkList.empty())
tryConvertIf(WorkList.pop_back_val());