[GVN] Make GVN aware of aligned_alloc

[bondhugula]

Summary

Make the GVN pass aware of aligned_alloc. There don't appear to be any
GVN test cases for malloc - this change is trivial and along the
same lines malloc/alloca are treated; a test case could be added when
it's added for the former.

Signed-off-by: Uday Bondhugula <[e-mail]>

Depends on D76974.

[bondhugula]

Add test case

[bondhugula]

Add test case (commit id change on rebase)

[xbolva00]

Prefix patch with [GVN] please.

OK.

[bondhugula]

In D76975#1951247, @xbolva00 wrote:

Prefix patch with [GVN] please.

OK.

Sure - does the prefix tag trigger any auto testing? GVN's already in the title.

[xbolva00]

No, it does not. However, it is a good practise to do so. :) in LLVM we usually prefix patches with pass name like GVN, InstCombine, etc..

llvm/lib/Transforms/Scalar/GVN.cpp

if (ORE->allowExtraAnalysis(DEBUG_TYPE))
       reportMayClobberedLoad(LI, DepInfo, DT, ORE);
 
     return false;
   }
   assert(DepInfo.isDef() && "follows from above");
 
   // Loading the allocation -> undef.
   if (isa<AllocaInst>(DepInst) || isMallocLikeFn(DepInst, TLI) ||
+      isAlignedAllocLikeFn(DepInst, TLI) ||
       // Loading immediately after lifetime begin -> undef.
       isLifetimeStart(DepInst)) {
     Res = AvailableValue::get(UndefValue::get(LI->getType()));
     return true;
   }
 
   // Loading from calloc (which zero initializes memory) -> zero
   if (isCallocLikeFn(DepInst, TLI)) {
static bool impliesEquivalanceIfFalse(CmpInst* Cmp) {
   // NaNs for unordered operators
   // +0.0 vs 0.0 for all operators
   if ((Cmp->getPredicate() == CmpInst::Predicate::FCMP_ONE &&
        Cmp->getFastMathFlags().noNaNs()) ||
       Cmp->getPredicate() == CmpInst::Predicate::FCMP_UNE) {
       Value *LHS = Cmp->getOperand(0);
       Value *RHS = Cmp->getOperand(1);
       // If we can prove either side non-zero, then equality must imply
-      // equivalence. 
+      // equivalence.
       // FIXME: We should do this optimization if 'no signed zeros' is
       // applicable via an instruction-level fast-math-flag or some other
       // indicator that relaxed FP semantics are being used.
       if (isa<ConstantFP>(LHS) && !cast<ConstantFP>(LHS)->isZero())
         return true;
       if (isa<ConstantFP>(RHS) && !cast<ConstantFP>(RHS)->isZero())
         return true;;
       // TODO: Handle vector floating point constants
bool GVN::processAssumeIntrinsic(IntrinsicInst *IntrinsicI) {
   // We can replace assume value with true, which covers cases like this:
   // call void @llvm.assume(i1 %cmp)
   // br i1 %cmp, label %bb1, label %bb2 ; will change %cmp to true
   ReplaceOperandsWithMap[V] = True;
 
   // If we find an equality fact, canonicalize all dominated uses in this block
   // to one of the two values.  We heuristically choice the "oldest" of the
   // two where age is determined by value number. (Note that propagateEquality
-  // above handles the cross block case.) 
-  // 
+  // above handles the cross block case.)
+  //
   // Key case to cover are:
-  // 1) 
+  // 1)
   // %cmp = fcmp oeq float 3.000000e+00, %0 ; const on lhs could happen
   // call void @llvm.assume(i1 %cmp)
   // ret float %0 ; will change it to ret float 3.000000e+00
   // 2)
   // %load = load float, float* %addr
   // %cmp = fcmp oeq float %load, %0
   // call void @llvm.assume(i1 %cmp)
   // ret float %load ; will change it to ret float %0
if (impliesEquivalanceIfTrue(CmpI)) {
       // removed a trivial assume yet.
       if (isa<Constant>(CmpLHS) && isa<Constant>(CmpRHS))
         return Changed;
 
       LLVM_DEBUG(dbgs() << "Replacing dominated uses of "
                  << *CmpLHS << " with "
                  << *CmpRHS << " in block "
                  << IntrinsicI->getParent()->getName() << "\n");
-      
 
       // Setup the replacement map - this handles uses within the same block
       if (hasUsersIn(CmpLHS, IntrinsicI->getParent()))
         ReplaceOperandsWithMap[CmpLHS] = CmpRHS;
 
       // NOTE: The non-block local cases are handled by the call to
       // propagateEquality above; this block is just about handling the block
       // local cases.  TODO: There's a bunch of logic in propagateEqualiy which
void GVN::assignBlockRPONumber(Function &F) {
   for (BasicBlock *BB : RPOT)
     BlockRPONumber[BB] = NextBlockNumber++;
   InvalidBlockRPONumbers = false;
 }
 
 bool GVN::replaceOperandsForInBlockEquality(Instruction *Instr) const {
   bool Changed = false;
   for (unsigned OpNum = 0; OpNum < Instr->getNumOperands(); ++OpNum) {
-    Value *Operand = Instr->getOperand(OpNum); 
+    Value *Operand = Instr->getOperand(OpNum);
     auto it = ReplaceOperandsWithMap.find(Operand);
     if (it != ReplaceOperandsWithMap.end()) {
       LLVM_DEBUG(dbgs() << "GVN replacing: " << *Operand << " with "
                         << *it->second << " in instruction " << *Instr << '\n');
       Instr->setOperand(OpNum, it->second);
       Changed = true;
     }
   }
while (!Worklist.empty()) {
     // If we are propagating an equality like "(A == B)" == "true" then also
     // propagate the equality A == B.  When propagating a comparison such as
     // "(A >= B)" == "true", replace all instances of "A < B" with "false".
     if (CmpInst *Cmp = dyn_cast<CmpInst>(LHS)) {
       Value *Op0 = Cmp->getOperand(0), *Op1 = Cmp->getOperand(1);
 
       // If "A == B" is known true, or "A != B" is known false, then replace
       // A with B everywhere in the scope.  For floating point operations, we
-      // have to be careful since equality does not always imply equivalance.  
+      // have to be careful since equality does not always imply equivalance.
       if ((isKnownTrue && impliesEquivalanceIfTrue(Cmp)) ||
           (isKnownFalse && impliesEquivalanceIfFalse(Cmp)))
         Worklist.push_back(std::make_pair(Op0, Op1));
 
       // If "A >= B" is known true, replace "A < B" with false everywhere.
       CmpInst::Predicate NotPred = Cmp->getInversePredicate();
       Constant *NotVal = ConstantInt::get(Cmp->getType(), isKnownFalse);
       // Since we don't have the instruction "A < B" immediately to hand, work

llvm/test/Transforms/GVN/malloc-load-removal.ll

 ; CHECK-LABEL: @test2(
 ; CHECK-NOT: load
 ; CHECK-NOT: icmp
 
 ; CHECK_NO_LIBCALLS-LABEL: @test2(
 ; CHECK_NO_LIBCALLS: load
 ; CHECK_NO_LIBCALLS: icmp
 }
+
+declare i8* @aligned_alloc(i64, i64) nounwind
+
+define noalias i8* @test3() nounwind uwtable ssp {
+entry:
+  %call = tail call i8* @aligned_alloc(i64 256, i64 32) nounwind
+  %0 = load i8, i8* %call, align 32
+  %tobool = icmp eq i8 %0, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  store i8 0, i8* %call, align 1
+  br label %if.end
+
+if.end:                                           ; preds = %if.then, %entry
+  ret i8* %call
+
+; CHECK-LABEL: @test3(
+; CHECK-NOT: load
+; CHECK-NOT: icmp
+
+; CHECK_NO_LIBCALLS-LABEL: @test3(
+; CHECK_NO_LIBCALLS: load
+; CHECK_NO_LIBCALLS: icmp
+}