Let each target determines whether a machine instruction is dead. If true, that allows late codeine passes to delete it.
This is considered a workaround. The problem is some targets are not modeling side effects correctly. PPC is apparently one of those. This patch allows ppc llvm-gcc to bootstrap on Darwin. Once we find out which instruction definitions are wrong, we can remove the PPCInstrInfo workaround.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76703 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/TargetInstrInfoImpl.cpp b/lib/CodeGen/TargetInstrInfoImpl.cpp
index 0b791e4..8aca0cc 100644
--- a/lib/CodeGen/TargetInstrInfoImpl.cpp
+++ b/lib/CodeGen/TargetInstrInfoImpl.cpp
@@ -139,6 +139,27 @@
MBB.insert(I, MI);
}
+bool TargetInstrInfoImpl::isDeadInstruction(const MachineInstr *MI) const {
+ const TargetInstrDesc &TID = MI->getDesc();
+ if (TID.mayLoad() || TID.mayStore() || TID.isCall() || TID.isTerminator() ||
+ TID.isCall() || TID.isBarrier() || TID.isReturn() ||
+ TID.hasUnmodeledSideEffects())
+ return false;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ const MachineOperand &MO = MI->getOperand(i);
+ if (!MO.isReg() || !MO.getReg())
+ continue;
+ if (MO.isDef() && !MO.isDead())
+ return false;
+ if (MO.isUse() && MO.isKill())
+ // FIXME: We can't remove kill markers or else the scavenger will assert.
+ // An alternative is to add a ADD pseudo instruction to replace kill
+ // markers.
+ return false;
+ }
+ return true;
+}
+
unsigned
TargetInstrInfoImpl::GetFunctionSizeInBytes(const MachineFunction &MF) const {
unsigned FnSize = 0;