[clang] [llvm] [InstCombine] remove dead loads, such as memcpy from undef (PR #143958)

[via llvm-commits]

github-actions[bot] wrote:

<!--LLVM CODE FORMAT COMMENT: {clang-format}-->


:warning: C/C++ code formatter, clang-format found issues in your code. :warning:

<details>
<summary>
You can test this locally with the following command:
</summary>

``````````bash
git-clang-format --diff HEAD~1 HEAD --extensions c,cpp -- clang/test/Misc/loop-opt-setup.c llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
``````````

</details>

<details>
<summary>
View the diff from clang-format here.
</summary>

``````````diff
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 83ebf9e40..f75e76f80 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3217,8 +3217,7 @@ static bool isRemovableWrite(CallBase &CB, Value *UsedV,
 
 static bool isAllocSiteRemovable(Instruction *AI,
                                  SmallVectorImpl<WeakTrackingVH> &Users,
-                                 const TargetLibraryInfo &TLI,
-                                 bool KnowInit) {
+                                 const TargetLibraryInfo &TLI, bool KnowInit) {
   SmallVector<Instruction*, 4> Worklist;
   const std::optional<StringRef> Family = getAllocationFamily(AI, &TLI);
   Worklist.push_back(AI);
@@ -3287,12 +3286,14 @@ static bool isAllocSiteRemovable(Instruction *AI,
             MemIntrinsic *MI = cast<MemIntrinsic>(II);
             if (MI->isVolatile())
               return false;
-            // Note: this could also be ModRef, but we can still interpret that as just Mod in that case.
-            ModRefInfo NewAccess = MI->getRawDest() == PI ? ModRefInfo::Mod : ModRefInfo::Ref;
+            // Note: this could also be ModRef, but we can still interpret that
+            // as just Mod in that case.
+            ModRefInfo NewAccess =
+                MI->getRawDest() == PI ? ModRefInfo::Mod : ModRefInfo::Ref;
             if ((Access & ~NewAccess) != ModRefInfo::NoModRef)
               return false;
             Access |= NewAccess;
-            }
+          }
             [[fallthrough]];
           case Intrinsic::assume:
           case Intrinsic::invariant_start:
@@ -3323,7 +3324,8 @@ static bool isAllocSiteRemovable(Instruction *AI,
           continue;
         }
 
-        if (!isRefSet(Access) && isRemovableWrite(*cast<CallBase>(I), PI, TLI)) {
+        if (!isRefSet(Access) &&
+            isRemovableWrite(*cast<CallBase>(I), PI, TLI)) {
           Access |= ModRefInfo::Mod;
           Users.emplace_back(I);
           continue;
@@ -3385,11 +3387,13 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
     DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false));
   }
 
-  // Determine what getInitialValueOfAllocation would return without actually allocating the result.
+  // Determine what getInitialValueOfAllocation would return without actually
+  // allocating the result.
   bool KnowInitUndef = isa<AllocaInst>(MI);
   bool KnowInitZero = false;
   if (!KnowInitUndef) {
-    Constant *Init = getInitialValueOfAllocation(&MI, &TLI, Type::getInt8Ty(MI.getContext()));
+    Constant *Init = getInitialValueOfAllocation(
+        &MI, &TLI, Type::getInt8Ty(MI.getContext()));
     if (Init) {
       if (isa<UndefValue>(Init))
         KnowInitUndef = true;
@@ -3422,10 +3426,10 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
           if (KnowInitZero && getUnderlyingObject(MTI->getRawDest()) != &MI) {
             IRBuilderBase::InsertPointGuard Guard(Builder);
             Builder.SetInsertPoint(MTI);
-            auto *M = Builder.CreateMemSet(MTI->getRawDest(),
-                    ConstantInt::get(Type::getInt8Ty(MI.getContext()), 0),
-                    MTI->getLength(),
-                    MTI->getDestAlign());
+            auto *M = Builder.CreateMemSet(
+                MTI->getRawDest(),
+                ConstantInt::get(Type::getInt8Ty(MI.getContext()), 0),
+                MTI->getLength(), MTI->getDestAlign());
             M->copyMetadata(*MTI, LLVMContext::MD_DIAssignID);
           }
         }
@@ -3454,7 +3458,8 @@ Instruction *InstCombinerImpl::visitAllocSite(Instruction &MI) {
         Constant *Replace;
         if (isa<LoadInst>(I)) {
           assert(KnowInitZero || KnowInitUndef);
-          Replace = KnowInitUndef ? UndefValue::get(I->getType()) : Constant::getNullValue(I->getType());
+          Replace = KnowInitUndef ? UndefValue::get(I->getType())
+                                  : Constant::getNullValue(I->getType());
         } else
           Replace = PoisonValue::get(I->getType());
         replaceInstUsesWith(*I, Replace);

``````````

</details>


https://github.com/llvm/llvm-project/pull/143958