[PATCH] D31581: perform DSE through invariant.group.barrier

[Piotr Padlewski via Phabricator via llvm-commits]

Prazek updated this revision to Diff 93817.
Prazek added a comment.

- format


https://reviews.llvm.org/D31581

Files:
  lib/Transforms/Scalar/DeadStoreElimination.cpp
  test/Transforms/DeadStoreElimination/invariant.group.barrier.ll


Index: test/Transforms/DeadStoreElimination/invariant.group.barrier.ll
===================================================================
--- /dev/null
+++ test/Transforms/DeadStoreElimination/invariant.group.barrier.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -basicaa -dse -S | FileCheck %s
+
+; CHECK-LABEL: void @skipBarrier(i8* %ptr)
+define void @skipBarrier(i8* %ptr) {
+; CHECK-NOT: store i8 42
+  store i8 42, i8* %ptr
+; CHECK: %ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
+  %ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
+; CHECK: store i8 43
+  store i8 43, i8* %ptr2
+  ret void
+}
+
+; CHECK-LABEL: void @skip2Barriers(i8* %ptr)
+define void @skip2Barriers(i8* %ptr) {
+; CHECK-NOT: store i8 42
+  store i8 42, i8* %ptr
+; CHECK: %ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
+  %ptr2 = call i8* @llvm.invariant.group.barrier(i8* %ptr)
+; CHECK-NOT: store i8 43
+  store i8 43, i8* %ptr2
+  %ptr3 = call i8* @llvm.invariant.group.barrier(i8* %ptr2)
+  %ptr4 = call i8* @llvm.invariant.group.barrier(i8* %ptr3)
+
+; CHECK: store i8 44
+  store i8 44, i8* %ptr4
+  ret void
+}
+
+declare i8* @llvm.invariant.group.barrier(i8*)
Index: lib/Transforms/Scalar/DeadStoreElimination.cpp
===================================================================
--- lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -295,13 +295,11 @@
 /// 'Earlier' location is completely overwritten by 'Later', 'OW_Begin' if the
 /// beginning of the 'Earlier' location is overwritten by 'Later', or
 /// 'OW_Unknown' if nothing can be determined.
-static OverwriteResult isOverwrite(const MemoryLocation &Later,
-                                   const MemoryLocation &Earlier,
-                                   const DataLayout &DL,
-                                   const TargetLibraryInfo &TLI,
-                                   int64_t &EarlierOff, int64_t &LaterOff,
-                                   Instruction *DepWrite,
-                                   InstOverlapIntervalsTy &IOL) {
+static OverwriteResult
+isOverwrite(const MemoryLocation &Later, const MemoryLocation &Earlier,
+            const DataLayout &DL, const TargetLibraryInfo &TLI,
+            int64_t &EarlierOff, int64_t &LaterOff, Instruction *DepWrite,
+            InstOverlapIntervalsTy &IOL, AliasAnalysis &AA) {
   // If we don't know the sizes of either access, then we can't do a comparison.
   if (Later.Size == MemoryLocation::UnknownSize ||
       Earlier.Size == MemoryLocation::UnknownSize)
@@ -312,7 +310,7 @@
 
   // If the start pointers are the same, we just have to compare sizes to see if
   // the later store was larger than the earlier store.
-  if (P1 == P2) {
+  if (P1 == P2 || AA.isMustAlias(P1, P2)) {
     // Make sure that the Later size is >= the Earlier size.
     if (Later.Size >= Earlier.Size)
       return OW_Complete;
@@ -1097,9 +1095,8 @@
       if (isRemovable(DepWrite) &&
           !isPossibleSelfRead(Inst, Loc, DepWrite, *TLI, *AA)) {
         int64_t InstWriteOffset, DepWriteOffset;
-        OverwriteResult OR =
-            isOverwrite(Loc, DepLoc, DL, *TLI, DepWriteOffset, InstWriteOffset,
-                        DepWrite, IOL);
+        OverwriteResult OR = isOverwrite(Loc, DepLoc, DL, *TLI, DepWriteOffset,
+                                         InstWriteOffset, DepWrite, IOL, *AA);
         if (OR == OW_Complete) {
           DEBUG(dbgs() << "DSE: Remove Dead Store:\n  DEAD: "
                 << *DepWrite << "\n  KILLER: " << *Inst << '\n');


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