[MergeFuncs] Don't introduce calls to (linkonce,weak)_odr functions.

clang/test/CodeGenCXX/merge-functions.cpp

@@ -1,6 +1,6 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O0 -fmerge-functions -emit-llvm -o - -x c++ < %s | FileCheck %s -implicit-check-not=_ZN1A1gEiPi
-// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O1 -fmerge-functions -emit-llvm -o - -x c++ < %s | FileCheck %s -implicit-check-not=_ZN1A1gEiPi
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O0 -fmerge-functions -emit-llvm -o - -x c++ < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O1 -fmerge-functions -emit-llvm -o - -x c++ < %s | FileCheck %s
 
 // Basic functionality test. Function merging doesn't kick in on functions that
 // are too simple.
@@ -10,4 +10,8 @@ struct A {
   virtual int g(int x, int *p) { return x ? *p : 1; }
 } a;
 
-// CHECK: define {{.*}} @_ZN1A1fEiPi
+// CHECK: define linkonce_odr noundef i32 @_ZN1A1gEiPi(
+// CHECK:   tail call noundef i32 @0(
+
+// CHECK: define linkonce_odr noundef i32 @_ZN1A1fEiPi(
+// CHECK:   tail call noundef i32 @0(

llvm/lib/Transforms/IPO/MergeFunctions.cpp

@@ -862,10 +862,20 @@ bool MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
   return false;
 }
 
+/// Returns true if \p F is either weak_odr or linkonce_odr.
+static bool isODR(const Function *F) {
+  return F->hasWeakODRLinkage() || F->hasLinkOnceODRLinkage();
+}
+
 // Merge two equivalent functions. Upon completion, Function G is deleted.
 void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
-  if (F->isInterposable()) {
-    assert(G->isInterposable());
+
+  // Create a new thunk that both F and G can call, if F cannot call G directly.
+  // That is the case if F is either interposable or if G is either weak_odr or
+  // linkonce_odr.
+  if (F->isInterposable() || (isODR(F) && isODR(G))) {
+    assert((!isODR(G) || isODR(F)) &&
+           "if G is ODR, F must also be ODR due to ordering");
 
     // Both writeThunkOrAlias() calls below must succeed, either because we can
     // create aliases for G and NewF, or because a thunk for F is profitable.
@@ -879,13 +889,22 @@ void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
                                       F->getAddressSpace(), "", F->getParent());
     NewF->copyAttributesFrom(F);
     NewF->takeName(F);
+    NewF->setComdat(F->getComdat());
+    F->setComdat(nullptr);
     NewF->IsNewDbgInfoFormat = F->IsNewDbgInfoFormat;
     // Ensure CFI type metadata is propagated to the new function.
     copyMetadataIfPresent(F, NewF, "type");
     copyMetadataIfPresent(F, NewF, "kcfi_type");
     removeUsers(F);
     F->replaceAllUsesWith(NewF);
 
+    // If G or NewF are (weak|linkonce)_odr, update all callers to call the
+    // thunk.
+    if (isODR(G))
+      replaceDirectCallers(G, F);
+    if (isODR(F))
+      replaceDirectCallers(NewF, F);
+
     // We collect alignment before writeThunkOrAlias that overwrites NewF and
     // G's content.
     const MaybeAlign NewFAlign = NewF->getAlign();
@@ -959,16 +978,24 @@ void MergeFunctions::replaceFunctionInTree(const FunctionNode &FN,
 
 // Ordering for functions that are equal under FunctionComparator
 static bool isFuncOrderCorrect(const Function *F, const Function *G) {
+  if (isODR(F) != isODR(G)) {
+    // ODR functions before non-ODR functions. A ODR function can call a non-ODR
+    // function if it is not interposable, but not the other way around.
+    return isODR(G);
+  }
+
   if (F->isInterposable() != G->isInterposable()) {
     // Strong before weak, because the weak function may call the strong
     // one, but not the other way around.
     return !F->isInterposable();
   }
+
   if (F->hasLocalLinkage() != G->hasLocalLinkage()) {
     // External before local, because we definitely have to keep the external
     // function, but may be able to drop the local one.
     return !F->hasLocalLinkage();
   }
+
   // Impose a total order (by name) on the replacement of functions. This is
   // important when operating on more than one module independently to prevent
   // cycles of thunks calling each other when the modules are linked together.

llvm/test/Transforms/MergeFunc/comdat.ll

@@ -19,6 +19,7 @@ define linkonce_odr hidden i32 @g(i32 %x, i32 %y) comdat {
   ret i32 %sum3
 }
 
-; CHECK-DAG: define linkonce_odr hidden i32 @f(i32 %x, i32 %y) comdat
-; CHECK-DAG: define linkonce_odr hidden i32 @g(i32 %0, i32 %1) comdat
+; CHECK-DAG: define private i32 @0(i32 %x, i32 %y) comdat($f)
+; CHECK-DAG: define linkonce_odr hidden i32 @g(i32 %0, i32 %1) comdat {
+; CHECK-DAG: define linkonce_odr hidden i32 @f(i32 %0, i32 %1) {
 

llvm/test/Transforms/MergeFunc/linkonce_odr.ll

@@ -1,20 +1,12 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --include-generated-funcs --version 5
 ; RUN: opt -S -passes=mergefunc < %s | FileCheck %s -implicit-check-not=funC
 
 ; Replacments should be totally ordered on the function name.
 ; If we don't do this we  can end up with one module defining a thunk for @funA
 ; and another module defining a thunk for @funB.
-;
 ; The problem with this is that the linker could then choose these two stubs
 ; each of the two modules and we end up with two stubs calling each other.
 
-; CHECK-LABEL: define linkonce_odr i32 @funA
-; CHECK-NEXT:    add
-; CHECK:         ret
-
-; CHECK-LABEL: define linkonce_odr i32 @funB
-; CHECK-NEXT:    tail call i32 @funA(i32 %0, i32 %1)
-; CHECK-NEXT:    ret
-
 define linkonce_odr i32 @funC(i32 %x, i32 %y) {
   %sum = add i32 %x, %y
   %sum2 = add i32 %x, %sum
@@ -40,3 +32,25 @@ define linkonce_odr i32 @funA(i32 %x, i32 %y) {
 ; @funC, however, can safely be deleted as it has no uses, and is discardable
 ; if unused.
 @take_addr_of_funB = global ptr @funB
+;.
+; CHECK: @take_addr_of_funB = global ptr @funB
+;.
+; CHECK-LABEL: define private i32 @0(
+; CHECK-SAME: i32 [[X:%.*]], i32 [[Y:%.*]]) {
+; CHECK-NEXT:    [[SUM:%.*]] = add i32 [[X]], [[Y]]
+; CHECK-NEXT:    [[SUM2:%.*]] = add i32 [[X]], [[SUM]]
+; CHECK-NEXT:    [[SUM3:%.*]] = add i32 [[X]], [[SUM2]]
+; CHECK-NEXT:    ret i32 [[SUM3]]
+;
+;
+; CHECK-LABEL: define linkonce_odr i32 @funC(
+; CHECK-SAME: i32 [[TMP0:%.*]], i32 [[TMP1:%.*]]) {
+; CHECK-NEXT:    [[TMP3:%.*]] = tail call i32 @[[GLOB0:[0-9]+]](i32 [[TMP0]], i32 [[TMP1]])
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;
+;
+; CHECK-LABEL: define linkonce_odr i32 @funB(
+; CHECK-SAME: i32 [[TMP0:%.*]], i32 [[TMP1:%.*]]) {
+; CHECK-NEXT:    [[TMP3:%.*]] = tail call i32 @[[GLOB0]](i32 [[TMP0]], i32 [[TMP1]])
+; CHECK-NEXT:    ret i32 [[TMP3]]
+;

llvm/test/Transforms/MergeFunc/merge-linkonce-odr-used.ll

@@ -0,0 +1,75 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --include-generated-funcs --version 5
+; RUN: opt -p mergefunc -S %s | FileCheck %s
+
+@llvm.used = appending global [3 x ptr] [ptr @linkonce_odr_caller_of_foo_1, ptr @linkonce_odr_caller_of_foo_2, ptr @linkonce_odr_caller_of_foo_3]
+
+define void @caller_of_callers(ptr %p) {
+  call void @linkonce_odr_caller_of_foo_1(ptr %p)
+  call void @linkonce_odr_caller_of_foo_2(ptr %p)
+  call void @linkonce_odr_caller_of_foo_3(ptr %p)
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr_caller_of_foo_1(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr_caller_of_foo_2(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr_caller_of_foo_3(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+declare void @foo(ptr)
+
+;.
+; CHECK: @llvm.used = appending global [3 x ptr] [ptr @linkonce_odr_caller_of_foo_1, ptr @linkonce_odr_caller_of_foo_2, ptr @linkonce_odr_caller_of_foo_3]
+;.
+; CHECK-LABEL: define void @caller_of_callers(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:    call void @[[GLOB0:[0-9]+]](ptr [[P]])
+; CHECK-NEXT:    call void @[[GLOB0]](ptr [[P]])
+; CHECK-NEXT:    call void @[[GLOB0]](ptr [[P]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define private void @0(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr void @linkonce_odr_caller_of_foo_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr void @linkonce_odr_caller_of_foo_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr void @linkonce_odr_caller_of_foo_3(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;

llvm/test/Transforms/MergeFunc/merge-linkonce-odr-weak-odr-mixed-used.ll

@@ -0,0 +1,75 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals all --include-generated-funcs --version 5
+; RUN: opt -p mergefunc -S %s | FileCheck %s
+
+@llvm.used = appending global [3 x ptr] [ptr @weak_odr_caller_of_foo_1, ptr @linkonce_odr_caller_of_foo_2, ptr @weak_odr_caller_of_foo_3]
+
+define void @caller_of_callers(ptr %p) {
+  call void @weak_odr_caller_of_foo_1(ptr %p)
+  call void @linkonce_odr_caller_of_foo_2(ptr %p)
+  call void @weak_odr_caller_of_foo_3(ptr %p)
+  ret void
+}
+
+define weak_odr void @weak_odr_caller_of_foo_1(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+define linkonce_odr void @linkonce_odr_caller_of_foo_2(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+define weak_odr void @weak_odr_caller_of_foo_3(ptr %p) {
+entry:
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  tail call void @foo(ptr %p)
+  ret void
+}
+
+declare void @foo(ptr)
+
+;.
+; CHECK: @llvm.used = appending global [3 x ptr] [ptr @weak_odr_caller_of_foo_1, ptr @linkonce_odr_caller_of_foo_2, ptr @weak_odr_caller_of_foo_3]
+;.
+; CHECK-LABEL: define void @caller_of_callers(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:    call void @[[GLOB0:[0-9]+]](ptr [[P]])
+; CHECK-NEXT:    call void @[[GLOB0]](ptr [[P]])
+; CHECK-NEXT:    call void @[[GLOB0]](ptr [[P]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define private void @0(
+; CHECK-SAME: ptr [[P:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    tail call void @foo(ptr [[P]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define weak_odr void @weak_odr_caller_of_foo_1(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define linkonce_odr void @linkonce_odr_caller_of_foo_2(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;
+;
+; CHECK-LABEL: define weak_odr void @weak_odr_caller_of_foo_3(
+; CHECK-SAME: ptr [[TMP0:%.*]]) {
+; CHECK-NEXT:    tail call void @[[GLOB0]](ptr [[TMP0]])
+; CHECK-NEXT:    ret void
+;