[ModRefInfo] Set ModRefInfo::Must for calls.

[asbirlea]

Summary

Follow-up patch to introducing Must in ModRefInfo, set the Must flag for a larger subset of calls.
Must is set if MustAlias and NoAlias is found (no May or Partial alias).

[sanjoy]

lib/Analysis/AliasAnalysis.cpp

193

Is this bit changing behavior? Both before and after we look at IsMustAlias only when DoesAlias is true, and your change only possibly changes the value of IsMustAlias in the cases where DoesAlias is false.

[asbirlea]

lib/Analysis/AliasAnalysis.cpp

193

Let me try to reason this out loud.
IsMustAlias &= (ArgAlias == MustAlias); is analogous with

if (ArgAlias != MustAlias)
    IsMustAlias = false

Before: IsMustAlias is set to false when NoAlias is found.
After patch: IsMustAlias is not set to false for NoAlias, because the statement moved inside the if (ArgAlias != NoAlias) block. IsMustAlias is now set to false for May/PartialAlias.

So for a list of arguments (a=MustAlias, b=NoAlias), DoesAlias will be set to true in the for loop because of a.
Before the patch, IsMustAlias=false because of b, while after the patch IsMustAlias=true because IsMustAlias &= (ArgAlias == MustAlias); only resets the value for May/PartialAlias, not for NoAlias.

Does this makes sense?

Calls were setting Must when all arguments were MustAlias, this patch enables mix of MustAlias and NoAlias arguments.
Updating patch description to reflect this.
I'll update the comment on the clearing statement too.

[asbirlea]

Update comments and summary.

[sanjoy]

The code itself lgtm (and sorry for the earlier braino), but it seems suspect to have MustAlias+NoAlias == MustAlias. For loads and stores I thought the rule was that "Ptr <MustAlias> Store" means "Store does not touch any location other than Ptr". However, this interpretation fails to justify what you're doing here -- if we have a call C = @f_argmemonly(p0, p1) and p1 mustlias p1 and noalias p0, we still can't return mustalias for the p0/C pair since @f_argmemonly(p0, p1) does touch a location other than p1 (i.e. p0). It could be that I'm missing something basic here, like last time.

lib/Analysis/AliasAnalysis.cpp

193

Sorry, I must have misread the code. This lgtm.

[asbirlea]

Let me start of with saying, I'm not sure this is the right thing to do, you're not missing anything (and sorry for the delayed reply).
The reason I say this, is that I've had the argument with myself both ways, and both make sense depending on how we end up using this Must bit information.

Taking your example, if we have a call C = @f_argmemonly(p0, p1) and p1 mustalias p1 and noalias p0, yes, @f_argmemonly(p0, p1) does touch p0.
If we look at something like promotion, p1 should be ok to be promoted to a scalar based on finding MustAlias+NoAlias with p0. I believe this was the original reason for this patch.
If we look at something like hoisting the call, then we need a getModRef result on all function arguments. This could potentially be an additional API call.

For 2 calls, there's another discussion. Before patch: Must set means "there is a single location both calls touch, and the calls touch no other locations."
After this patch: Must set means "there exists at least one memory location that is touched by both calls, and both calls may each touch a set of disjoint memory locations".
I'm not sure how to use either info off the top of my head, so can't make the argument for/against here..

lib/Analysis/AliasAnalysis.cpp

if (doesAccessArgPointees(MRB)) {
       for (auto AI = CS.arg_begin(), AE = CS.arg_end(); AI != AE; ++AI) {
         const Value *Arg = *AI;
         if (!Arg->getType()->isPointerTy())
           continue;
         unsigned ArgIdx = std::distance(CS.arg_begin(), AI);
         MemoryLocation ArgLoc = MemoryLocation::getForArgument(CS, ArgIdx, TLI);
         AliasResult ArgAlias = alias(ArgLoc, Loc);
         if (ArgAlias != NoAlias) {
           ModRefInfo ArgMask = getArgModRefInfo(CS, ArgIdx);
           DoesAlias = true;
           AllArgsMask = unionModRef(AllArgsMask, ArgMask);
-        }
           // Conservatively clear IsMustAlias unless only MustAlias is found.
           IsMustAlias &= (ArgAlias == MustAlias);
         }
       }
+    }
     // Return NoModRef if no alias found with any argument.
     if (!DoesAlias)
       return ModRefInfo::NoModRef;
     // Logical & between other AA analyses and argument analysis.
     Result = intersectModRef(Result, AllArgsMask);
     // If only MustAlias found above, set Must bit.
     Result = IsMustAlias ? setMust(Result) : clearMust(Result);
   }
for (auto I = CS2.arg_begin(), E = CS2.arg_end(); I != E; ++I) {
         ArgMask = ModRefInfo::Mod;
 
       // ModRefCS1 indicates what CS1 might do to CS2ArgLoc, and we use
       // above ArgMask to update dependence info.
       ModRefInfo ModRefCS1 = getModRefInfo(CS1, CS2ArgLoc);
       ArgMask = intersectModRef(ArgMask, ModRefCS1);
 
       // Conservatively clear IsMustAlias unless only MustAlias is found.
+      // If ArgMask has Mod/Ref set, then alias exists. ArgModRefCS2 never
+      // has Must set, ModRefCS1 may have Must set.
+      if (isModOrRefSet(ArgMask))
         IsMustAlias &= isMustSet(ModRefCS1);
 
       R = intersectModRef(unionModRef(R, ArgMask), Result);
       if (R == Result) {
         // On early exit, not all args were checked, cannot set Must.
         if (I + 1 != E)
           IsMustAlias = false;
         break;
       }
for (auto I = CS1.arg_begin(), E = CS1.arg_end(); I != E; ++I) {
       auto CS1ArgLoc = MemoryLocation::getForArgument(CS1, CS1ArgIdx, TLI);
 
       // ArgModRefCS1 indicates what CS1 might do to CS1ArgLoc; if CS1 might
       // Mod CS1ArgLoc, then we care about either a Mod or a Ref by CS2. If
       // CS1 might Ref, then we care only about a Mod by CS2.
       ModRefInfo ArgModRefCS1 = getArgModRefInfo(CS1, CS1ArgIdx);
       ModRefInfo ModRefCS2 = getModRefInfo(CS2, CS1ArgLoc);
       if ((isModSet(ArgModRefCS1) && isModOrRefSet(ModRefCS2)) ||
-          (isRefSet(ArgModRefCS1) && isModSet(ModRefCS2)))
+          (isRefSet(ArgModRefCS1) && isModSet(ModRefCS2))) {
         R = intersectModRef(unionModRef(R, ArgModRefCS1), Result);
 
         // Conservatively clear IsMustAlias unless only MustAlias is found.
         IsMustAlias &= isMustSet(ModRefCS2);
+      }
 
       if (R == Result) {
         // On early exit, not all args were checked, cannot set Must.
         if (I + 1 != E)
           IsMustAlias = false;
         break;
       }
     }
if (!(*CI)->getType()->isPointerTy() ||
          ArgNo < CS.getNumArgOperands() && !CS.isByValArgument(ArgNo)))
       continue;
 
     AliasResult AR = alias(MemoryLocation(*CI), MemoryLocation(Object));
     // If this is a no-capture pointer argument, see if we can tell that it
     // is impossible to alias the pointer we're checking.  If not, we have to
     // assume that the call could touch the pointer, even though it doesn't
     // escape.
-    if (AR != MustAlias)
-      MustAlias = false;
     if (AR == NoAlias)
       continue;
+    if (AR != MustAlias)
+      MustAlias = false;
     if (CS.doesNotAccessMemory(ArgNo))
       continue;
     if (CS.onlyReadsMemory(ArgNo)) {
       R = ModRefInfo::Ref;
       continue;
     }
     // Not returning MustModRef since we have not seen all the arguments.
     return ModRefInfo::ModRef;

lib/Analysis/BasicAliasAnalysis.cpp

for (auto CI = CS.data_operands_begin(), CE = CS.data_operands_end();
       // if it aliases with Object.
       if (CS.doesNotAccessMemory(OperandNo))
         continue;
 
       // If this is a no-capture pointer argument, see if we can tell that it
       // is impossible to alias the pointer we're checking.
       AliasResult AR =
           getBestAAResults().alias(MemoryLocation(*CI), MemoryLocation(Object));
-      if (AR != MustAlias)
-        IsMustAlias = false;
+
       // Operand doesnt alias 'Object', continue looking for other aliases
       if (AR == NoAlias)
         continue;
+      if (AR == MayAlias || AR == PartialAlias)
+        IsMustAlias = false;
       // Operand aliases 'Object', but call doesn't modify it. Strengthen
       // initial assumption and keep looking in case if there are more aliases.
       if (CS.onlyReadsMemory(OperandNo)) {
         Result = setRef(Result);
         continue;
       }
       // Operand aliases 'Object' but call only writes into it.
       if (CS.doesNotReadMemory(OperandNo)) {
         Result = setMod(Result);
         continue;
       }
       // This operand aliases 'Object' and call reads and writes into it.
-      // Setting ModRef will not yield an early return below, MustAlias is not
+      // Setting ModRef will not yield an early return below, IsMustAlias is not
       // used further.
       Result = ModRefInfo::ModRef;
       break;
     }
 
     // No operand aliases, reset Must bit. Add below if at least one aliases
     // and all aliases found are MustAlias.
     if (isNoModRef(Result))
ModRefInfo BasicAAResult::getModRefInfo(ImmutableCallSite CS,
   // If Loc must-aliases either one of these two locations, then it necessarily
   // no-aliases the other.
   if (auto *Inst = dyn_cast<MemCpyInst>(CS.getInstruction())) {
     AliasResult SrcAA, DestAA;
 
     if ((SrcAA = getBestAAResults().alias(MemoryLocation::getForSource(Inst),
                                           Loc)) == MustAlias)
       // Loc is exactly the memcpy source thus disjoint from memcpy dest.
-      return ModRefInfo::Ref;
+      return ModRefInfo::MustRef;
     if ((DestAA = getBestAAResults().alias(MemoryLocation::getForDest(Inst),
                                            Loc)) == MustAlias)
       // The converse case.
-      return ModRefInfo::Mod;
+      return ModRefInfo::MustMod;
 
     // It's also possible for Loc to alias both src and dest, or neither.
     ModRefInfo rv = ModRefInfo::NoModRef;
     if (SrcAA != NoAlias)
       rv = setRef(rv);
     if (DestAA != NoAlias)
       rv = setMod(rv);
     return rv;

test/Analysis/BasicAA/cs-cs.ll

 define void @test2a(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test2a:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test2b(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   %R = getelementptr i8, i8* %P, i64 12
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test2b:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
 ; CHECK: NoAlias:      i8* %P, i8* %R
 ; CHECK: NoAlias:      i8* %Q, i8* %R
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test2c(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   %R = getelementptr i8, i8* %P, i64 11
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test2c:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
 ; CHECK: NoAlias:      i8* %P, i8* %R
 ; CHECK: NoAlias:      i8* %Q, i8* %R
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test2d(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   %R = getelementptr i8, i8* %P, i64 -12
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test2d:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
 ; CHECK: NoAlias:      i8* %P, i8* %R
 ; CHECK: NoAlias:      i8* %Q, i8* %R
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test2e(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   %R = getelementptr i8, i8* %P, i64 -11
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test2e:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
 ; CHECK: NoAlias:      i8* %P, i8* %R
 ; CHECK: NoAlias:      i8* %Q, i8* %R
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %R        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %R, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test3(i8* %P, i8* %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   ret void

 define void @test3a(i8* noalias %P, i8* noalias %Q) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test3a:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 8, i32 1, i1 false)
 }
 
 define void @test4(i8* %P, i8* noalias %Q) #3 {
   tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false)
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test4:
 
 ; CHECK: NoAlias:      i8* %P, i8* %Q
 ; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %Q        <->  tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q        <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memset.p0i8.i64(i8* %P, i8 42, i64 8, i32 1, i1 false)
 }
 
 define void @test5(i8* %P, i8* %Q, i8* %R) #3 {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test5:
define void @test5a(i8* noalias %P, i8* noalias %Q, i8* noalias %R) nounwind ssp {
   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
   ret void
 
 ; CHECK-LABEL: Function: test5a:
 
 ; CHECK: NoAlias:     i8* %P, i8* %Q
 ; CHECK: NoAlias:     i8* %P, i8* %R
 ; CHECK: NoAlias:     i8* %Q, i8* %R
-; CHECK: Just Mod:  Ptr: i8* %P     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %Q     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %Q     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %R     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:  Ptr: i8* %P     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):  Ptr: i8* %P     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
 ; CHECK: NoModRef:  Ptr: i8* %Q     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
-; CHECK: Just Ref:  Ptr: i8* %R     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
-; CHECK: Just Mod:   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
+; CHECK: Just Ref (MustAlias):  Ptr: i8* %R     <->  tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false)
+; CHECK: Just Mod (MustAlias):   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %R, i64 12, i32 1, i1 false) <->   tail call void @llvm.memcpy.p0i8.p0i8.i64(i8* %P, i8* %Q, i64 12, i32 1, i1 false)
 }
 
 define void @test6(i8* %P) #3 {
   call void @llvm.memset.p0i8.i64(i8* %P, i8 -51, i64 32, i32 8, i1 false)
   call void @a_readonly_func(i8* %P)
   ret void
 
 ; CHECK-LABEL: Function: test6:

 ;; test that MustAlias is set for calls when no MayAlias is found.
 declare void @another_argmemonly_func(i8*, i8*) #0
 define void @test8a(i8* noalias %p, i8* noalias %q) {
 entry:
   call void @another_argmemonly_func(i8* %p, i8* %q)
   ret void
 
 ; CHECK-LABEL: Function: test8a
-; CHECK: Both ModRef:  Ptr: i8* %p <->  call void @another_argmemonly_func(i8* %p, i8* %q)
-; CHECK: Both ModRef:  Ptr: i8* %q <->  call void @another_argmemonly_func(i8* %p, i8* %q)
+; CHECK: Both ModRef (MustAlias):  Ptr: i8* %p <->  call void @another_argmemonly_func(i8* %p, i8* %q)
+; CHECK: Both ModRef (MustAlias):  Ptr: i8* %q <->  call void @another_argmemonly_func(i8* %p, i8* %q)
 }
 define void @test8b(i8* %p, i8* %q) {
 entry:
   call void @another_argmemonly_func(i8* %p, i8* %q)
   ret void
 
 ; CHECK-LABEL: Function: test8b
 ; CHECK: Both ModRef:  Ptr: i8* %p <->  call void @another_argmemonly_func(i8* %p, i8* %q)