[llvm] 1074010 - [NFC][DSE] Clean up KnownNoReads and MemorySSAScanLimit in DSE

[Dawid Jurczak via llvm-commits]

Author: Dawid Jurczak
Date: 2021-08-14T11:26:57+02:00
New Revision: 107401002eab206b3a255a2d9bb8c2c3fb54cae5

URL: https://github.com/llvm/llvm-project/commit/107401002eab206b3a255a2d9bb8c2c3fb54cae5
DIFF: https://github.com/llvm/llvm-project/commit/107401002eab206b3a255a2d9bb8c2c3fb54cae5.diff

LOG: [NFC][DSE] Clean up KnownNoReads and MemorySSAScanLimit in DSE

Another simple cleanups set in DSE. CheckCache is removed since 1f1145006b32 and in consequence KnownNoReads is useless.
Also update description of MemorySSAScanLimit which default value is 150 instead 100.

Differential Revision: https://reviews.llvm.org/D107812

Added: 
    

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

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
index b315ecf63c96..1bc4a3886dec 100644
--- a/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -124,7 +124,7 @@ EnablePartialStoreMerging("enable-dse-partial-store-merging",
 static cl::opt<unsigned>
     MemorySSAScanLimit("dse-memoryssa-scanlimit", cl::init(150), cl::Hidden,
                        cl::desc("The number of memory instructions to scan for "
-                                "dead store elimination (default = 100)"));
+                                "dead store elimination (default = 150)"));
 static cl::opt<unsigned> MemorySSAUpwardsStepLimit(
     "dse-memoryssa-walklimit", cl::init(90), cl::Hidden,
     cl::desc("The maximum number of steps while walking upwards to find "
@@ -1501,11 +1501,6 @@ struct DSEState {
     };
     PushMemUses(EarlierAccess);
 
-    // Optimistically collect all accesses for reads. If we do not find any
-    // read clobbers, add them to the cache.
-    SmallPtrSet<MemoryAccess *, 16> KnownNoReads;
-    if (!EarlierMemInst->mayReadFromMemory())
-      KnownNoReads.insert(EarlierAccess);
     // Check if EarlierDef may be read.
     for (unsigned I = 0; I < WorkList.size(); I++) {
       MemoryAccess *UseAccess = WorkList[I];
@@ -1518,7 +1513,6 @@ struct DSEState {
       }
       --ScanLimit;
       NumDomMemDefChecks++;
-      KnownNoReads.insert(UseAccess);
 
       if (isa<MemoryPhi>(UseAccess)) {
         if (any_of(KillingDefs, [this, UseAccess](Instruction *KI) {