Revert change 335077 "[InlineSpiller] Fix a crash due to lack of forward progress from remat specifically for STATEPOINT"

    
This change caused widespread assertion failures in our downstream testing:
lib/CodeGen/LiveInterval.cpp:409: bool llvm::LiveRange::overlapsFrom(const llvm::LiveRange&, llvm::LiveRange::const_iterator) const: Assertion `!empty() && "empty range"' failed.

llvm-svn: 335462

1 files changed, 0 insertions, 26 deletions

diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 56704a606a1..007e9283d83 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -215,7 +215,6 @@ private:
   void eliminateRedundantSpills(LiveInterval &LI, VNInfo *VNI);
 
   void markValueUsed(LiveInterval*, VNInfo*);
-  bool canGuaranteeAssignmentAfterRemat(unsigned VReg, MachineInstr &MI);
   bool reMaterializeFor(LiveInterval &, MachineInstr &MI);
   void reMaterializeAll();
 
@@ -515,26 +514,6 @@ void InlineSpiller::markValueUsed(LiveInterval *LI, VNInfo *VNI) {
   } while (!WorkList.empty());
 }
 
-bool InlineSpiller::canGuaranteeAssignmentAfterRemat(unsigned VReg,
-                                                     MachineInstr &MI) {
-  // Here's a quick explanation of the problem we're trying to handle here:
-  // * There are some pseudo instructions with more vreg uses than there are
-  //   physical registers on the machine.
-  // * This is normally handled by spilling the vreg, and folding the reload
-  //   into the user instruction.  (Thus decreasing the number of used vregs
-  //   until the remainder can be assigned to physregs.)
-  // * However, since we may try to spill vregs in any order, we can end up
-  //   trying to spill each operand to the instruction, and then rematting it
-  //   instead.  When that happens, the new live intervals (for the remats) are
-  //   expected to be trivially assignable (i.e. RS_Done).  However, since we
-  //   may have more remats than physregs, we're guaranteed to fail to assign
-  //   one.
-  // At the moment, we only handle this for STATEPOINTs since they're the only
-  // psuedo op where we've seen this.  If we start seeing other instructions
-  // with the same problem, we need to revisit this.
-  return (MI.getOpcode() != TargetOpcode::STATEPOINT);
-}
-
 /// reMaterializeFor - Attempt to rematerialize before MI instead of reloading.
 bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg, MachineInstr &MI) {
   // Analyze instruction
@@ -590,11 +569,6 @@ bool InlineSpiller::reMaterializeFor(LiveInterval &VirtReg, MachineInstr &MI) {
     return true;
   }
 
-  // If we can't guarantee that we'll be able to actually assign the new vreg,
-  // we can't remat.
-  if (!canGuaranteeAssignmentAfterRemat(VirtReg.reg, MI))
-    return false;
-
   // Allocate a new register for the remat.
   unsigned NewVReg = Edit->createFrom(Original);