[PATCH] D101044: [NFC][DSE]Change 'do-while' to 'for' loop to simplify code structure

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ebrevnov created this revision.
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With 'for' loop there is is a single place where 'Current' is adjusted. It helps to avoid copy paste and makes a bit easy to understand overall loop controll flow.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D101044

Files:
  llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp


Index: llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -1302,13 +1302,11 @@
 
     MemoryAccess *Current = StartAccess;
     Instruction *KillingI = KillingDef->getMemoryInst();
-    bool StepAgain;
     LLVM_DEBUG(dbgs() << "  trying to get dominating access\n");
 
     // Find the next clobbering Mod access for DefLoc, starting at StartAccess.
     Optional<MemoryLocation> CurrentLoc;
-    do {
-      StepAgain = false;
+    for (;; Current = cast<MemoryDef>(Current)->getDefiningAccess()) {
       LLVM_DEBUG({
         dbgs() << "   visiting " << *Current;
         if (!MSSA.isLiveOnEntryDef(Current) && isa<MemoryUseOrDef>(Current))
@@ -1347,8 +1345,6 @@
       Instruction *CurrentI = CurrentDef->getMemoryInst();
 
       if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO))) {
-        StepAgain = true;
-        Current = CurrentDef->getDefiningAccess();
         continue;
       }
 
@@ -1387,16 +1383,12 @@
       // If Current cannot be analyzed or is not removable, check the next
       // candidate.
       if (!hasAnalyzableMemoryWrite(CurrentI, TLI) || !isRemovable(CurrentI)) {
-        StepAgain = true;
-        Current = CurrentDef->getDefiningAccess();
         continue;
       }
 
       // If Current does not have an analyzable write location, skip it
       CurrentLoc = getLocForWriteEx(CurrentI);
       if (!CurrentLoc) {
-        StepAgain = true;
-        Current = CurrentDef->getDefiningAccess();
         continue;
       }
 
@@ -1405,8 +1397,6 @@
       // memory location and not multiple locations in a loop.
       if (Current->getBlock() != KillingDef->getBlock() &&
           !IsGuaranteedLoopInvariant(const_cast<Value *>(CurrentLoc->Ptr))) {
-        StepAgain = true;
-        Current = CurrentDef->getDefiningAccess();
         WalkerStepLimit -= 1;
         continue;
       }
@@ -1416,10 +1406,9 @@
         // the next candidate if the current Current does not write the same
         // underlying object as the terminator.
         if (!isMemTerminator(*CurrentLoc, CurrentI, KillingI)) {
-          StepAgain = true;
-          Current = CurrentDef->getDefiningAccess();
+          continue;
         }
-        continue;
+        break;
       } else {
         int64_t InstWriteOffset, DepWriteOffset;
         auto OR = isOverwrite(KillingI, CurrentI, DefLoc, *CurrentLoc, DL, TLI,
@@ -1427,23 +1416,23 @@
         // If Current does not write to the same object as KillingDef, check
         // the next candidate.
         if (OR == OW_Unknown) {
-          StepAgain = true;
-          Current = CurrentDef->getDefiningAccess();
+          continue;
         } else if (OR == OW_MaybePartial) {
           // If KillingDef only partially overwrites Current, check the next
           // candidate if the partial step limit is exceeded. This aggressively
           // limits the number of candidates for partial store elimination,
           // which are less likely to be removable in the end.
           if (PartialLimit <= 1) {
-            StepAgain = true;
-            Current = CurrentDef->getDefiningAccess();
             WalkerStepLimit -= 1;
             continue;
           }
           PartialLimit -= 1;
+          break;
+        } else {
+          break;
         }
       }
-    } while (StepAgain);
+    };
 
     // Accesses to objects accessible after the function returns can only be
     // eliminated if the access is killed along all paths to the exit. Collect


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