[PATCH] D141153: [LocalStackSlotAllocation] Minor simplifications. NFC

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: arsenm, john.brawn, reames, MatzeB.
Herald added subscribers: StephenFan, hiraditya.
Herald added a project: All.
craig.topper requested review of this revision.
Herald added a subscriber: wdng.
Herald added a project: LLVM.

Instead of maintaining a separate valid flag for BaseReg, Use
BaseReg.isValid(). I think this is left over from an older
implementation that maintained a vector of base registers.

The other change is not do a speculative assignment to BaseOffset
that needs to be reverted. Only commit it after we do the check.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D141153

Files:
  llvm/lib/CodeGen/LocalStackSlotAllocation.cpp


Index: llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
===================================================================
--- llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
+++ llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
@@ -288,7 +288,6 @@
   // stack frame. If it wants one, re-use a suitable one we've previously
   // allocated, or if there isn't one that fits the bill, allocate a new one
   // and ask the target to create a defining instruction for it.
-  bool UsedBaseReg = false;
 
   MachineFrameInfo &MFI = Fn.getFrameInfo();
   const TargetRegisterInfo *TRI = Fn.getSubtarget().getRegisterInfo();
@@ -386,7 +385,7 @@
     // instruction itself will be taken into account by the target,
     // so we don't have to adjust for it here when reusing a base
     // register.
-    if (UsedBaseReg &&
+    if (BaseReg.isValid() &&
         lookupCandidateBaseReg(BaseReg, BaseOffset, FrameSizeAdjust,
                                LocalOffset, MI, TRI)) {
       LLVM_DEBUG(dbgs() << "  Reusing base register " << BaseReg << "\n");
@@ -396,8 +395,7 @@
       // No previously defined register was in range, so create a new one.
       int64_t InstrOffset = TRI->getFrameIndexInstrOffset(&MI, idx);
 
-      int64_t PrevBaseOffset = BaseOffset;
-      BaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset;
+      int64_t CandBaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset;
 
       // We'd like to avoid creating single-use virtual base registers.
       // Because the FrameRefs are in sorted order, and we've already
@@ -406,12 +404,13 @@
       // then don't bother creating it.
       if (ref + 1 >= e ||
           !lookupCandidateBaseReg(
-              BaseReg, BaseOffset, FrameSizeAdjust,
+              BaseReg, CandBaseOffset, FrameSizeAdjust,
               FrameReferenceInsns[ref + 1].getLocalOffset(),
-              *FrameReferenceInsns[ref + 1].getMachineInstr(), TRI)) {
-        BaseOffset = PrevBaseOffset;
+              *FrameReferenceInsns[ref + 1].getMachineInstr(), TRI))
         continue;
-      }
+
+      // Save the base offset.
+      BaseOffset = CandBaseOffset;
 
       // Tell the target to insert the instruction to initialize
       // the base register.
@@ -428,9 +427,8 @@
       Offset = -InstrOffset;
 
       ++NumBaseRegisters;
-      UsedBaseReg = true;
     }
-    assert(BaseReg && "Unable to allocate virtual base register!");
+    assert(BaseReg.isValid() && "Unable to allocate virtual base register!");
 
     // Modify the instruction to use the new base register rather
     // than the frame index operand.
@@ -440,5 +438,5 @@
     ++NumReplacements;
   }
 
-  return UsedBaseReg;
+  return BaseReg.isValid();
 }


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