If fast-isel fails, remove dead instructions generated during the failed
attempt.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145425 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 2087a1b..b4946ec 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -66,6 +66,7 @@
"target-independent selector");
STATISTIC(NumFastIselSuccessTarget, "Number of insts selected by "
"target-specific selector");
+STATISTIC(NumFastIselDead, "Number of dead insts removed on failure");
/// startNewBlock - Set the current block to which generated machine
/// instructions will be appended, and clear the local CSE map.
@@ -309,6 +310,18 @@
++FuncInfo.InsertPt;
}
+void FastISel::removeDeadCode(MachineBasicBlock::iterator I,
+ MachineBasicBlock::iterator E) {
+ assert (I && E && std::distance(I, E) > 0 && "Invalid iterator!");
+ while (I != E) {
+ MachineInstr *Dead = &*I;
+ ++I;
+ Dead->eraseFromParent();
+ ++NumFastIselDead;
+ }
+ recomputeInsertPt();
+}
+
FastISel::SavePoint FastISel::enterLocalValueArea() {
MachineBasicBlock::iterator OldInsertPt = FuncInfo.InsertPt;
DebugLoc OldDL = DL;
@@ -794,19 +807,33 @@
DL = I->getDebugLoc();
+ MachineBasicBlock::iterator SavedInsertPt = FuncInfo.InsertPt;
+
// First, try doing target-independent selection.
if (SelectOperator(I, I->getOpcode())) {
++NumFastIselSuccessIndependent;
DL = DebugLoc();
return true;
}
+ // Remove dead code. However, ignore call instructions since we've flushed
+ // the local value map and recomputed the insert point.
+ if (!isa<CallInst>(I)) {
+ recomputeInsertPt();
+ if (SavedInsertPt != FuncInfo.InsertPt)
+ removeDeadCode(FuncInfo.InsertPt, SavedInsertPt);
+ }
// Next, try calling the target to attempt to handle the instruction.
+ SavedInsertPt = FuncInfo.InsertPt;
if (TargetSelectInstruction(I)) {
++NumFastIselSuccessTarget;
DL = DebugLoc();
return true;
}
+ // Check for dead code and remove as necessary.
+ recomputeInsertPt();
+ if (SavedInsertPt != FuncInfo.InsertPt)
+ removeDeadCode(FuncInfo.InsertPt, SavedInsertPt);
DL = DebugLoc();
return false;