[llvm] 2a24d35 - [MachineCombine] add a hook for resource length limit

[Chen Zheng via llvm-commits]

Author: Chen Zheng
Date: 2020-05-31T23:21:04-04:00
New Revision: 2a24d350dbeacb131af91e8c438fed2bd81698c0

URL: https://github.com/llvm/llvm-project/commit/2a24d350dbeacb131af91e8c438fed2bd81698c0
DIFF: https://github.com/llvm/llvm-project/commit/2a24d350dbeacb131af91e8c438fed2bd81698c0.diff

LOG: [MachineCombine] add a hook for resource length limit

Added: 
    

Modified: 
    llvm/include/llvm/CodeGen/TargetInstrInfo.h
    llvm/lib/CodeGen/MachineCombiner.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/CodeGen/TargetInstrInfo.h b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
index 8c6d84521594..709030b62076 100644
--- a/llvm/include/llvm/CodeGen/TargetInstrInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetInstrInfo.h
@@ -1093,6 +1093,9 @@ class TargetInstrInfo : public MCInstrInfo {
                       SmallVectorImpl<MachineInstr *> &DelInstrs,
                       DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const;
 
+  /// The limit on resource length extension we accept in MachineCombiner Pass.
+  virtual int getExtendResourceLenLimit() const { return 0; }
+
   /// This is an architecture-specific helper function of reassociateOps.
   /// Set special operand attributes for new instructions after reassociation.
   virtual void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,

diff  --git a/llvm/lib/CodeGen/MachineCombiner.cpp b/llvm/lib/CodeGen/MachineCombiner.cpp
index 73895bdf834f..34087d0491bd 100644
--- a/llvm/lib/CodeGen/MachineCombiner.cpp
+++ b/llvm/lib/CodeGen/MachineCombiner.cpp
@@ -406,12 +406,14 @@ bool MachineCombiner::preservesResourceLen(
                     << ResLenBeforeCombine
                     << " and after: " << ResLenAfterCombine << "\n";);
   LLVM_DEBUG(
-      ResLenAfterCombine <= ResLenBeforeCombine
+      ResLenAfterCombine <=
+      ResLenBeforeCombine + TII->getExtendResourceLenLimit()
           ? dbgs() << "\t\t  As result it IMPROVES/PRESERVES Resource Length\n"
           : dbgs() << "\t\t  As result it DOES NOT improve/preserve Resource "
                       "Length\n");
 
-  return ResLenAfterCombine <= ResLenBeforeCombine;
+  return ResLenAfterCombine <=
+         ResLenBeforeCombine + TII->getExtendResourceLenLimit();
 }
 
 /// \returns true when new instruction sequence should be generated