[llvm] 8597458 - [regalloc] Fix assertion error when LiveInterval is empty

[via llvm-commits]

Author: wangpc
Date: 2022-01-26T14:06:57+08:00
New Revision: 8597458278027047c06a1a81579893335e761a33

URL: https://github.com/llvm/llvm-project/commit/8597458278027047c06a1a81579893335e761a33
DIFF: https://github.com/llvm/llvm-project/commit/8597458278027047c06a1a81579893335e761a33.diff

LOG: [regalloc] Fix assertion error when LiveInterval is empty

When evicting interference, it causes an asseertion error
since LiveIntervals::intervalIsInOneMBB assumes that input
is not empty.

This patch fixed bug mentioned in D118020.

Reviewed By: MatzeB

Differential Revision: https://reviews.llvm.org/D118124

Added: 
    

Modified: 
    llvm/lib/CodeGen/LiveIntervals.cpp
    llvm/lib/CodeGen/RegAllocGreedy.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp
index 2f97386b6d189..9571afa434c12 100644
--- a/llvm/lib/CodeGen/LiveIntervals.cpp
+++ b/llvm/lib/CodeGen/LiveIntervals.cpp
@@ -827,6 +827,8 @@ void LiveIntervals::addKillFlags(const VirtRegMap *VRM) {
 
 MachineBasicBlock*
 LiveIntervals::intervalIsInOneMBB(const LiveInterval &LI) const {
+  assert(!LI.empty() && "LiveInterval is empty.");
+
   // A local live range must be fully contained inside the block, meaning it is
   // defined and killed at instructions, not at block boundaries. It is not
   // live in or out of any block.

diff  --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
index 79314874093fb..6ea6dbcbbb743 100644
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -497,7 +497,7 @@ bool DefaultEvictionAdvisor::canEvictInterferenceBasedOnCost(
   if (Matrix->checkInterference(VirtReg, PhysReg) > LiveRegMatrix::IK_VirtReg)
     return false;
 
-  bool IsLocal = LIS->intervalIsInOneMBB(VirtReg);
+  bool IsLocal = VirtReg.empty() || LIS->intervalIsInOneMBB(VirtReg);
 
   // Find VirtReg's cascade number. This will be unassigned if VirtReg was never
   // involved in an eviction before. If a cascade number was assigned, deny