In split module utility we should never separate alias with its aliasee.

[slarin]

Summary

When splitting module with preserving locals, we currently do not handle case of global alias being separated with its aliasee.

[mehdi_amini]

LGTM

[slarin]

Thanks Mehdi. I will let some time for Peter to comment if he pleases...

Sergei

[pcc]

lib/Transforms/Utils/SplitModule.cpp

94

An aliasee can be something other than a GlobalValue (for example, it could be a ConstantInt or a GEP ConstantExpr). I think what you want here is getBaseObject.

[slarin]

Implement Peters comments.

[pcc]

lib/Transforms/Utils/SplitModule.cpp

95

You no longer need this cast.

test/tools/llvm-split/scc-global-alias.ll

23

Please add a test case with a non-GlobalValue constant.

[slarin]

Make sure all kind of alisees are handled + test.

[slarin]

Peter,

Can this be landed now...?

Thanks.

Sergei

---

Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation

[pcc]

LGTM after dealing with comment.

test/tools/llvm-split/scc-const-alias.ll

24

This isn't quite what I meant. I meant e.g.

@g1Alias = internal alias i8, bitcast (i32* @g1 to i8*)
@constAlias = internal alias i8, inttoptr (i64 42 to i8*)

[slarin]

Updated test.

lib/Transforms/Utils/SplitModule.cpp

auto recordGVSet = [&GVtoClusterMap, &ComdatMembers](GlobalValue &GV) {
     if (const Comdat *C = GV.getComdat()) {
       auto &Member = ComdatMembers[C];
       if (Member)
         GVtoClusterMap.unionSets(Member, &GV);
       else
         Member = &GV;
     }
 
+    // For aliases we should not separate them from their aliasees regardless
+    // of linkage.
+    if (GlobalAlias *GA = dyn_cast<GlobalAlias>(&GV)) {
+      if (const GlobalObject *Base = GA->getBaseObject())
+        GVtoClusterMap.unionSets(&GV, Base);
+    }
+
     // Further only iterate over local GVs.
     if (!GV.hasLocalLinkage())
       return;
 
     for (auto *U : GV.users()) {
       SmallVector<const User *, 4> Worklist;
       Worklist.push_back(U);
       while (!Worklist.empty()) {

test/tools/llvm-split/scc-const-alias.ll

+; We should never separate alias from aliasee.
+; RUN: llvm-split -j=3 -preserve-locals -o %t %s
+; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 %s
+; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 %s
+; RUN: llvm-dis -o - %t2 | FileCheck --check-prefix=CHECK2 %s
+
+; Checks are not critical here - verifier will assert if we fail.
+; CHECK0: @g1 = global i32 99
+; CHECK0: @c1 = external constant i32
+; CHECK0: @c1Alias = external global i32
+; CHECK0: @g1Alias = internal alias i32, i32* @g1
+
+; CHECK1: @c1 = constant i32 0
+; CHECK1: @c1Alias = internal alias i32, i32* @c1
+
+; CHECK2: @g1 = external global i32
+; CHECK2: @g1Alias = external global i32
+
+@g1 = global i32 99
+@c1 = constant i32 0
+
+@g1Alias = internal alias i32, i32* @g1
+@c1Alias = internal alias i32, i32* @c1
+@funExternalAlias = alias i32 (), i32 ()* @funExternal
+
+define i32 @funExternal() {
+entry:
+  %x = load i32, i32* @g1Alias
+  ret i32 %x
+}
+
+define i32 @funExternal2() {
+entry:
+  %x = load i32, i32* @c1Alias
+  %y = call i32 @funExternalAlias()
+  %z = add i32 %x, %y
+  ret i32 %z
+}

test/tools/llvm-split/scc-global-alias.ll

+; We should never separate alias from aliasee.
+; RUN: llvm-split -j=3 -preserve-locals -o %t %s
+; RUN: llvm-dis -o - %t0 | FileCheck --check-prefix=CHECK0 %s
+; RUN: llvm-dis -o - %t1 | FileCheck --check-prefix=CHECK1 %s
+; RUN: llvm-dis -o - %t2 | FileCheck --check-prefix=CHECK2 %s
+
+; Checks are not critical here - verifier will assert if we fail.
+; CHECK0: @funInternal2Alias = alias
+; CHECK0: @funExternal2Alias = alias
+; CHECK0: define internal i32 @funInternal2
+; CHECK0: define i32 @funExternal2
+
+; CHECK1: @funInternalAlias = alias
+; CHECK1: define internal i32 @funInternal
+
+; CHECK2: @funExternalAlias = alias
+; CHECK2: define i32 @funExternal
+
+@funInternalAlias = alias i32 (), i32 ()* @funInternal
+@funExternalAlias = alias i32 (), i32 ()* @funExternal
+@funInternal2Alias = alias i32 (), i32 ()* @funInternal2
+@funExternal2Alias = alias i32 (), i32 ()* @funExternal2
+
+define internal i32 @funInternal() {
+entry:
+  ret i32 0
+}
+
+define i32 @funExternal() {
+entry:
+  %x = call i32 @funInternalAlias()
+  ret i32 %x
+}
+
+define internal i32 @funInternal2() {
+entry:
+  %x = call i32 @funInternalAlias()
+  ret i32 %x
+}
+
+define i32 @funExternal2() {
+entry:
+  %x = call i32 @funInternal2()
+  %y = call i32 @funExternalAlias()
+  %z = add nsw i32 %x, %y
+  ret i32 %z
+}