[PATCH] D101440: [DSE} Eliminate store after callo (PR50143)

[Dávid Bolvanský via Phabricator via llvm-commits]

xbolva00 created this revision.
xbolva00 added reviewers: fhahn, jdoerfert.
Herald added a subscriber: hiraditya.
xbolva00 requested review of this revision.
Herald added a project: LLVM.
Herald added a subscriber: llvm-commits.

https://reviews.llvm.org/D101440

Files:
  llvm/lib/Analysis/AliasAnalysis.cpp
  llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
  llvm/test/Transforms/DeadStoreElimination/noop-stores.ll


Index: llvm/test/Transforms/DeadStoreElimination/noop-stores.ll
===================================================================
--- llvm/test/Transforms/DeadStoreElimination/noop-stores.ll
+++ llvm/test/Transforms/DeadStoreElimination/noop-stores.ll
@@ -313,7 +313,6 @@
 define i8* @store_zero_after_calloc_inaccessiblememonly() {
 ; CHECK-LABEL: @store_zero_after_calloc_inaccessiblememonly(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @calloc(i64 1, i64 10) #[[ATTR6:[0-9]+]]
-; CHECK-NEXT:    store i8 0, i8* [[CALL]], align 1
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call i8* @calloc(i64 1, i64 10)  inaccessiblememonly
@@ -407,7 +406,6 @@
 define i8* @zero_memset_after_calloc_inaccessiblememonly()  {
 ; CHECK-LABEL: @zero_memset_after_calloc_inaccessiblememonly(
 ; CHECK-NEXT:    [[CALL:%.*]] = tail call i8* @calloc(i64 10000, i64 4) #[[ATTR6]]
-; CHECK-NEXT:    call void @llvm.memset.p0i8.i64(i8* [[CALL]], i8 0, i64 40000, i1 false)
 ; CHECK-NEXT:    ret i8* [[CALL]]
 ;
   %call = tail call i8* @calloc(i64 10000, i64 4) inaccessiblememonly
Index: llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
+++ llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
@@ -926,13 +926,17 @@
 }
 
 // Check if we can ignore \p D for DSE.
-bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller) {
+bool canSkipDef(MemoryDef *D, bool DefVisibleToCaller,
+                const TargetLibraryInfo &TLI) {
   Instruction *DI = D->getMemoryInst();
   // Calls that only access inaccessible memory cannot read or write any memory
   // locations we consider for elimination.
   if (auto *CB = dyn_cast<CallBase>(DI))
-    if (CB->onlyAccessesInaccessibleMemory())
+    if (CB->onlyAccessesInaccessibleMemory()) {
+      if (isAllocLikeFn(DI, &TLI))
+        return false;
       return true;
+    }
 
   // We can eliminate stores to locations not visible to the caller across
   // throwing instructions.
@@ -948,7 +952,7 @@
     return true;
 
   // Skip intrinsics that do not really read or modify memory.
-  if (isNoopIntrinsic(D->getMemoryInst()))
+  if (isNoopIntrinsic(DI))
     return true;
 
   return false;
@@ -1243,8 +1247,11 @@
       return false;
 
     if (auto *CB = dyn_cast<CallBase>(UseInst))
-      if (CB->onlyAccessesInaccessibleMemory())
+      if (CB->onlyAccessesInaccessibleMemory()) {
+        if (isAllocLikeFn(CB, &TLI))
+          return true;
         return false;
+      }
 
     // NOTE: For calls, the number of stores removed could be slightly improved
     // by using AA.callCapturesBefore(UseInst, DefLoc, &DT), but that showed to
@@ -1346,7 +1353,7 @@
       MemoryDef *CurrentDef = cast<MemoryDef>(Current);
       Instruction *CurrentI = CurrentDef->getMemoryInst();
 
-      if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO))) {
+      if (canSkipDef(CurrentDef, !isInvisibleToCallerBeforeRet(DefUO), TLI)) {
         StepAgain = true;
         Current = CurrentDef->getDefiningAccess();
         continue;
Index: llvm/lib/Analysis/AliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/AliasAnalysis.cpp
+++ llvm/lib/Analysis/AliasAnalysis.cpp
@@ -30,6 +30,7 @@
 #include "llvm/Analysis/CFLSteensAliasAnalysis.h"
 #include "llvm/Analysis/CaptureTracking.h"
 #include "llvm/Analysis/GlobalsModRef.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/Analysis/MemoryLocation.h"
 #include "llvm/Analysis/ObjCARCAliasAnalysis.h"
 #include "llvm/Analysis/ScalarEvolutionAliasAnalysis.h"
@@ -237,7 +238,7 @@
   // aggregate set of AA results.
   auto MRB = getModRefBehavior(Call);
   if (onlyAccessesInaccessibleMem(MRB))
-    return ModRefInfo::NoModRef;
+    return isAllocLikeFn(Call, &TLI) ? ModRefInfo::Mod : ModRefInfo::NoModRef;
 
   if (onlyReadsMemory(MRB))
     Result = clearMod(Result);


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