[llvm] r367169 - [TargetLowering] Add depth limit to SimplifyMultipleUseDemandedBits

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Sat Jul 27 05:23:36 2019
New Revision: 367169

URL: http://llvm.org/viewvc/llvm-project?rev=367169&view=rev
Log:
[TargetLowering] Add depth limit to SimplifyMultipleUseDemandedBits

We're getting reports of massive compile time increases because SimplifyMultipleUseDemandedBits was losing track of the depth and not earlying-out. No repro yet, but consider this a pre-emptive commit.

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp?rev=367169&r1=367168&r2=367169&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/TargetLowering.cpp Sat Jul 27 05:23:36 2019
@@ -569,6 +569,9 @@ bool TargetLowering::SimplifyDemandedBit
 SDValue TargetLowering::SimplifyMultipleUseDemandedBits(
     SDValue Op, const APInt &DemandedBits, const APInt &DemandedElts,
     SelectionDAG &DAG, unsigned Depth) const {
+  if (Depth == 6) // Limit search depth.
+    return SDValue();
+
   KnownBits LHSKnown, RHSKnown;
   switch (Op.getOpcode()) {
   case ISD::AND: {