Dissallow non-empty metadata for invariant.group

Summary:
This feature is not needed, but it might be usefull in the future
to use metadata to mark what which function should support it
(and strip it when not).

Reviewers: rsmith, sanjoy, amharc, kuhar

Subscribers: hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D45419

llvm-svn: 332787

llvm/docs/LangRef.rst

@@ -5314,10 +5314,10 @@ Irreducible loop header weights are typically based on profile data.
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 The experimental ``invariant.group`` metadata may be attached to 
-``load``/``store`` instructions.
+``load``/``store`` instructions referencing a single metadata with no entries.
 The existence of the ``invariant.group`` metadata on the instruction tells
 the optimizer that every ``load`` and ``store`` to the same pointer operand
-within the same invariant group can be assumed to load or store the same
+can be assumed to load or store the same
 value (but see the ``llvm.launder.invariant.group`` intrinsic which affects
 when two pointers are considered the same). Pointers returned by bitcast or
 getelementptr with only zero indices are considered the same.
@@ -5334,7 +5334,6 @@ Examples:
 
    %a = load i8, i8* %ptr, !invariant.group !0 ; Can assume that value under %ptr didn't change
    call void @foo(i8* %ptr)
-   %b = load i8, i8* %ptr, !invariant.group !1 ; Can't assume anything, because group changed
 
    %newPtr = call i8* @getPointer(i8* %ptr)
    %c = load i8, i8* %newPtr, !invariant.group !0 ; Can't assume anything, because we only have information about %ptr
@@ -5351,8 +5350,7 @@ Examples:
    declare i8* @getPointer(i8*)
    declare i8* @llvm.launder.invariant.group(i8*)
 
-   !0 = !{!"magic ptr"}
-   !1 = !{!"other ptr"}
+   !0 = !{}
 
 The invariant.group metadata must be dropped when replacing one pointer by
 another based on aliasing information. This is because invariant.group is tied
@@ -7637,7 +7635,8 @@ referenced by the load contains the same value at all points in the
 program where the memory location is known to be dereferenceable.
 
 The optional ``!invariant.group`` metadata must reference a single metadata name
- ``<index>`` corresponding to a metadata node. See ``invariant.group`` metadata.
+ ``<index>`` corresponding to a metadata node with no entries.
+ See ``invariant.group`` metadata.
 
 The optional ``!nonnull`` metadata must reference a single
 metadata name ``<index>`` corresponding to a metadata node with no

llvm/docs/ReleaseNotes.rst

@@ -109,6 +109,8 @@ Changes to the LLVM IR
 
 * invariant.group.barrier has been renamed to launder.invariant.group.
 
+* invariant.group metadata can now refer only empty metadata nodes.
+
 Changes to the ARM Backend
 --------------------------
 

llvm/lib/Analysis/MemoryDependenceAnalysis.cpp

@@ -355,8 +355,8 @@ MemDepResult MemoryDependenceResults::getPointerDependencyFrom(
 MemDepResult
 MemoryDependenceResults::getInvariantGroupPointerDependency(LoadInst *LI,
                                                             BasicBlock *BB) {
-  auto *InvariantGroupMD = LI->getMetadata(LLVMContext::MD_invariant_group);
-  if (!InvariantGroupMD)
+
+  if (!LI->getMetadata(LLVMContext::MD_invariant_group))
     return MemDepResult::getUnknown();
 
   // Take the ptr operand after all casts and geps 0. This way we can search
@@ -417,7 +417,7 @@ MemoryDependenceResults::getInvariantGroupPointerDependency(LoadInst *LI,
       // same pointer operand) we can assume that value pointed by pointer
       // operand didn't change.
       if ((isa<LoadInst>(U) || isa<StoreInst>(U)) &&
-          U->getMetadata(LLVMContext::MD_invariant_group) == InvariantGroupMD)
+          U->getMetadata(LLVMContext::MD_invariant_group) != nullptr)
         ClosestDependency = GetClosestDependency(ClosestDependency, U);
     }
   }

llvm/test/Transforms/CodeGenPrepare/invariant.group.ll

@@ -11,7 +11,7 @@ enter:
   %val = load i8, i8* @tmp, !invariant.group !0, !tbaa !{!1, !1, i64 0}
   %ptr = call i8* @llvm.launder.invariant.group.p0i8(i8* @tmp)
 
-  ; CHECK: store i8 42, i8* @tmp
+  ; CHECK: store i8 42, i8* @tmp{{$}}
   store i8 42, i8* %ptr, !invariant.group !0
 
   ret void
@@ -20,5 +20,5 @@ enter:
 
 declare i8* @llvm.launder.invariant.group.p0i8(i8*)
 
-!0 = !{!"something"}
+!0 = !{}
 !1 = !{!"x", !0}

llvm/test/Transforms/GVN/invariant.group.ll

@@ -74,7 +74,7 @@ entry:
   %2 = bitcast %struct.A* %1 to i8***
 
 ; CHECK: %vtable = load {{.*}} !invariant.group
-  %vtable = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable = load i8**, i8*** %2, align 8, !invariant.group !0
   %cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
   call void @llvm.assume(i1 %cmp.vtables)
 
@@ -83,29 +83,29 @@ entry:
   %4 = bitcast %struct.A* %3 to void (%struct.A*)***
 
 ; CHECK: call void @_ZN1A3fooEv(
-  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
+  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !0
   %vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
   %5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
   call void %5(%struct.A* %3)
   %6 = load %struct.A*, %struct.A** %a, align 8
   %7 = bitcast %struct.A* %6 to void (%struct.A*)***
 
 ; CHECK: call void @_ZN1A3fooEv(
-  %vtable2 = load void (%struct.A*)**, void (%struct.A*)*** %7, align 8, !invariant.group !2
+  %vtable2 = load void (%struct.A*)**, void (%struct.A*)*** %7, align 8, !invariant.group !0
   %vfn3 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable2, i64 0
   %8 = load void (%struct.A*)*, void (%struct.A*)** %vfn3, align 8
 
   call void %8(%struct.A* %6)
   %9 = load %struct.A*, %struct.A** %a, align 8
   %10 = bitcast %struct.A* %9 to void (%struct.A*)***
 
-  %vtable4 = load void (%struct.A*)**, void (%struct.A*)*** %10, align 8, !invariant.group !2
+  %vtable4 = load void (%struct.A*)**, void (%struct.A*)*** %10, align 8, !invariant.group !0
   %vfn5 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable4, i64 0
   %11 = load void (%struct.A*)*, void (%struct.A*)** %vfn5, align 8
 ; CHECK: call void @_ZN1A3fooEv(
   call void %11(%struct.A* %9)
 
-  %vtable5 = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable5 = load i8**, i8*** %2, align 8, !invariant.group !0
   %vfn6 = getelementptr inbounds i8*, i8** %vtable5, i64 0
   %12 = bitcast i8** %vfn6 to void (%struct.A*)**
   %13 = load void (%struct.A*)*, void (%struct.A*)** %12, align 8
@@ -127,15 +127,15 @@ entry:
   %2 = bitcast %struct.A* %1 to i8***
 
 ; CHECK: %vtable = load {{.*}} !invariant.group
-  %vtable = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable = load i8**, i8*** %2, align 8, !invariant.group !0
   %cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
 
   store %struct.A* %1, %struct.A** %a, align 8
 ; CHECK-NOT: !invariant.group
   %3 = load %struct.A*, %struct.A** %a, align 8
   %4 = bitcast %struct.A* %3 to void (%struct.A*)***
 
-  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
+  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !0
   %vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
   %5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
   call void %5(%struct.A* %3)
@@ -152,7 +152,7 @@ enter:
 ; CHECK: %[[A:.*]] = load i8, i8* %ptr, !invariant.group
   %a = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
-  %b = load i8, i8* %ptr, !invariant.group !1
+  %b = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[A]])
   call void @bar(i8 %a)
 ; CHECK: call void @bar(i8 %[[A]])
@@ -169,7 +169,7 @@ enter:
 ; CHECK: %[[D:.*]] = load i8, i8* %ptr, !invariant.group
   %c = load i8, i8* %ptr
 ; CHECK-NOT: load
-  %d = load i8, i8* %ptr, !invariant.group !1
+  %d = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[D]])
   call void @bar(i8 %c)
 ; CHECK: call void @bar(i8 %[[D]])
@@ -184,7 +184,7 @@ enter:
   store i8 42, i8* %ptr
   call void @foo(i8* %ptr)
 ; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group
-  %e = load i8, i8* %ptr, !invariant.group !1
+  %e = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
   %f = load i8, i8* %ptr
 ; CHECK: call void @bar(i8 %[[E]])
@@ -200,10 +200,10 @@ enter:
   %ptr = alloca i8
   store i8 42, i8* %ptr
   call void @foo(i8* %ptr)
-; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group ![[OneMD:[0-9]]]
-  %e = load i8, i8* %ptr, !invariant.group !1
+; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group
+  %e = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
-  %f = load i8, i8* %ptr, !invariant.group !1
+  %f = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[E]])
   call void @bar(i8 %e)
 ; CHECK: call void @bar(i8 %[[E]])
@@ -298,12 +298,7 @@ entry:
     %a = load i8, i8* %ptr, !invariant.group !0 ; Can assume that value under %ptr didn't change
 ; CHECK: call void @bar(i8 42)
     call void @bar(i8 %a)
-
-    call void @foo(i8* %ptr)
-    %b = load i8, i8* %ptr, !invariant.group !1 ; Can't assume anything, because group changed
-; CHECK: call void @bar(i8 %b)
-    call void @bar(i8 %b)
-
+
     %newPtr = call i8* @getPointer(i8* %ptr) 
     %c = load i8, i8* %newPtr, !invariant.group !0 ; Can't assume anything, because we only have information about %ptr
 ; CHECK: call void @bar(i8 %c)
@@ -448,7 +443,4 @@ declare void @llvm.assume(i1 %cmp.vtables) #0
 
 
 attributes #0 = { nounwind }
-; CHECK: ![[OneMD]] = !{!"other ptr"}
-!0 = !{!"magic ptr"}
-!1 = !{!"other ptr"}
-!2 = !{!"vtable_of_a"}
+!0 = !{}

llvm/test/Transforms/GlobalOpt/invariant.group.barrier.ll

@@ -76,4 +76,4 @@ declare void @changeTmp3ValAndCallBarrierInside()
 
 declare i8* @llvm.launder.invariant.group(i8*)
 
-!0 = !{!"something"}
+!0 = !{}

llvm/test/Transforms/NewGVN/invariant.group.ll

@@ -75,7 +75,7 @@ entry:
   %2 = bitcast %struct.A* %1 to i8***
 
 ; CHECK: %vtable = load {{.*}} !invariant.group
-  %vtable = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable = load i8**, i8*** %2, align 8, !invariant.group !0
   %cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
   call void @llvm.assume(i1 %cmp.vtables)
 
@@ -84,29 +84,29 @@ entry:
   %4 = bitcast %struct.A* %3 to void (%struct.A*)***
 
 ; CHECK: call void @_ZN1A3fooEv(
-  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
+  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !0
   %vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
   %5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
   call void %5(%struct.A* %3)
   %6 = load %struct.A*, %struct.A** %a, align 8
   %7 = bitcast %struct.A* %6 to void (%struct.A*)***
 
 ; CHECK: call void @_ZN1A3fooEv(
-  %vtable2 = load void (%struct.A*)**, void (%struct.A*)*** %7, align 8, !invariant.group !2
+  %vtable2 = load void (%struct.A*)**, void (%struct.A*)*** %7, align 8, !invariant.group !0
   %vfn3 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable2, i64 0
   %8 = load void (%struct.A*)*, void (%struct.A*)** %vfn3, align 8
 
   call void %8(%struct.A* %6)
   %9 = load %struct.A*, %struct.A** %a, align 8
   %10 = bitcast %struct.A* %9 to void (%struct.A*)***
 
-  %vtable4 = load void (%struct.A*)**, void (%struct.A*)*** %10, align 8, !invariant.group !2
+  %vtable4 = load void (%struct.A*)**, void (%struct.A*)*** %10, align 8, !invariant.group !0
   %vfn5 = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable4, i64 0
   %11 = load void (%struct.A*)*, void (%struct.A*)** %vfn5, align 8
 ; CHECK: call void @_ZN1A3fooEv(
   call void %11(%struct.A* %9)
 
-  %vtable5 = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable5 = load i8**, i8*** %2, align 8, !invariant.group !0
   %vfn6 = getelementptr inbounds i8*, i8** %vtable5, i64 0
   %12 = bitcast i8** %vfn6 to void (%struct.A*)**
   %13 = load void (%struct.A*)*, void (%struct.A*)** %12, align 8
@@ -128,15 +128,15 @@ entry:
   %2 = bitcast %struct.A* %1 to i8***
 
 ; CHECK: %vtable = load {{.*}} !invariant.group
-  %vtable = load i8**, i8*** %2, align 8, !invariant.group !2
+  %vtable = load i8**, i8*** %2, align 8, !invariant.group !0
   %cmp.vtables = icmp eq i8** %vtable, getelementptr inbounds ([3 x i8*], [3 x i8*]* @_ZTV1A, i64 0, i64 2)
 
   store %struct.A* %1, %struct.A** %a, align 8
 ; CHECK-NOT: !invariant.group
   %3 = load %struct.A*, %struct.A** %a, align 8
   %4 = bitcast %struct.A* %3 to void (%struct.A*)***
 
-  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !2
+  %vtable1 = load void (%struct.A*)**, void (%struct.A*)*** %4, align 8, !invariant.group !0
   %vfn = getelementptr inbounds void (%struct.A*)*, void (%struct.A*)** %vtable1, i64 0
   %5 = load void (%struct.A*)*, void (%struct.A*)** %vfn, align 8
   call void %5(%struct.A* %3)
@@ -153,7 +153,7 @@ enter:
 ; CHECK: %[[A:.*]] = load i8, i8* %ptr, !invariant.group
   %a = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
-  %b = load i8, i8* %ptr, !invariant.group !1
+  %b = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[A]])
   call void @bar(i8 %a)
 ; CHECK: call void @bar(i8 %[[A]])
@@ -170,7 +170,7 @@ enter:
 ; CHECK: %[[D:.*]] = load i8, i8* %ptr, !invariant.group
   %c = load i8, i8* %ptr
 ; CHECK-NOT: load
-  %d = load i8, i8* %ptr, !invariant.group !1
+  %d = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[D]])
   call void @bar(i8 %c)
 ; CHECK: call void @bar(i8 %[[D]])
@@ -185,7 +185,7 @@ enter:
   store i8 42, i8* %ptr
   call void @foo(i8* %ptr)
 ; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group
-  %e = load i8, i8* %ptr, !invariant.group !1
+  %e = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
   %f = load i8, i8* %ptr
 ; CHECK: call void @bar(i8 %[[E]])
@@ -201,10 +201,10 @@ enter:
   %ptr = alloca i8
   store i8 42, i8* %ptr
   call void @foo(i8* %ptr)
-; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group ![[OneMD:[0-9]]]
-  %e = load i8, i8* %ptr, !invariant.group !1
+; CHECK: %[[E:.*]] = load i8, i8* %ptr, !invariant.group
+  %e = load i8, i8* %ptr, !invariant.group !0
 ; CHECK-NOT: load
-  %f = load i8, i8* %ptr, !invariant.group !1
+  %f = load i8, i8* %ptr, !invariant.group !0
 ; CHECK: call void @bar(i8 %[[E]])
   call void @bar(i8 %e)
 ; CHECK: call void @bar(i8 %[[E]])
@@ -244,6 +244,7 @@ entry:
     %ptr = alloca i8
     store i8 42, i8* %ptr, !invariant.group !0
     %ptr2 = call i8* @llvm.launder.invariant.group.p0i8(i8* %ptr)
+; CHECK-NOT: load
     %a = load i8, i8* %ptr2, !invariant.group !0
 
 ; CHECK: ret i8 42
@@ -298,12 +299,7 @@ entry:
     %a = load i8, i8* %ptr, !invariant.group !0 ; Can assume that value under %ptr didn't change
 ; CHECK: call void @bar(i8 42)
     call void @bar(i8 %a)
-
-    call void @foo(i8* %ptr)
-    %b = load i8, i8* %ptr, !invariant.group !1 ; Can't assume anything, because group changed
-; CHECK: call void @bar(i8 %b)
-    call void @bar(i8 %b)
-
+
     %newPtr = call i8* @getPointer(i8* %ptr) 
     %c = load i8, i8* %newPtr, !invariant.group !0 ; Can't assume anything, because we only have information about %ptr
 ; CHECK: call void @bar(i8 %c)
@@ -448,7 +444,4 @@ declare void @llvm.assume(i1 %cmp.vtables) #0
 
 
 attributes #0 = { nounwind }
-; CHECK: ![[OneMD]] = !{!"other ptr"}
-!0 = !{!"magic ptr"}
-!1 = !{!"other ptr"}
-!2 = !{!"vtable_of_a"}
+!0 = !{}