[RegAlloc] Make sure live-ranges reflect the state of the IR when removing them

When removing a live-range we used to not touch them making debug
prints harder to read because the IR was not matching what the
live-ranges information was saying.

This only affects debug printing and allows to put stronger asserts in
the code (see r308906 for instance).

llvm-svn: 311401

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/RegAllocBasic.cpp b/llvm/lib/CodeGen/RegAllocBasic.cpp
index 774306154a8..5ecde0c9d9f 100644
--- a/llvm/lib/CodeGen/RegAllocBasic.cpp
+++ b/llvm/lib/CodeGen/RegAllocBasic.cpp
@@ -143,14 +143,17 @@ INITIALIZE_PASS_END(RABasic, "regallocbasic", "Basic Register Allocator", false,
                     false)
 
 bool RABasic::LRE_CanEraseVirtReg(unsigned VirtReg) {
+  LiveInterval &LI = LIS->getInterval(VirtReg);
   if (VRM->hasPhys(VirtReg)) {
-    LiveInterval &LI = LIS->getInterval(VirtReg);
     Matrix->unassign(LI);
     aboutToRemoveInterval(LI);
     return true;
   }
   // Unassigned virtreg is probably in the priority queue.
   // RegAllocBase will erase it after dequeueing.
+  // Nonetheless, clear the live-range so that the debug
+  // dump will show the right state for that VirtReg.
+  LI.clear();
   return false;
 }