[MergeFuncs] Generate alias instead of thunk if possible
The MergeFunctions pass was originally intended to emit aliases
instead of thunks where possible (unnamed_addr). However, for a
long time this functionality was behind a flag hardcoded to false,
bitrotted and was eventually removed in r309313.
Originally the functionality was first disabled in r108417 due to
lack of support for aliases in Mach-O. I believe that this is no
longer the case nowadays, but not really familiar with this area.
In the interest of being conservative, this patch reintroduces the
aliasing functionality behind a default disabled -mergefunc-use-aliases
flag.
Differential Revision: https://reviews.llvm.org/D53285
llvm-svn: 347407
diff --git a/llvm/test/Transforms/MergeFunc/alias.ll b/llvm/test/Transforms/MergeFunc/alias.ll
new file mode 100644
index 0000000..ee1c7af
--- /dev/null
+++ b/llvm/test/Transforms/MergeFunc/alias.ll
@@ -0,0 +1,116 @@
+; RUN: opt -S -mergefunc -mergefunc-use-aliases < %s | FileCheck %s
+
+; Aliases should always be created for the weak functions, and
+; for external functions if there is no local function
+
+; CHECK: @external_external_2 = unnamed_addr alias void (float*), bitcast (void (i32*)* @external_external_1 to void (float*)*)
+; CHECK: @weak_weak_2 = weak unnamed_addr alias void (float*), bitcast (void (i32*)* @0 to void (float*)*)
+; CHECK: @weak_weak_1 = weak unnamed_addr alias void (i32*), void (i32*)* @0
+; CHECK: @weak_external_1 = weak unnamed_addr alias void (i32*), bitcast (void (float*)* @weak_external_2 to void (i32*)*)
+; CHECK: @external_weak_2 = weak unnamed_addr alias void (float*), bitcast (void (i32*)* @external_weak_1 to void (float*)*)
+; CHECK: @weak_internal_1 = weak unnamed_addr alias void (i32*), bitcast (void (float*)* @weak_internal_2 to void (i32*)*)
+; CHECK: @internal_weak_2 = weak unnamed_addr alias void (float*), bitcast (void (i32*)* @internal_weak_1 to void (float*)*)
+
+; A strong backing function had to be created for the weak-weak pair
+
+; CHECK: define private void @0(i32* %a) unnamed_addr
+; CHECK_NEXT: call void @dummy4()
+
+; These internal functions are dropped in favor of the external ones
+
+; CHECK-NOT: define internal void @external_internal_2(float *%a) unnamed_addr
+; CHECK-NOT: define internal void @internal_external_1(i32 *%a) unnamed_addr
+; CHECK-NOT: define internal void @internal_external_1(i32 *%a) unnamed_addr
+; CHECK-NOT: define internal void @internal_external_2(float *%a) unnamed_addr
+
+; Only used to mark which functions should be merged.
+declare void @dummy1()
+declare void @dummy2()
+declare void @dummy3()
+declare void @dummy4()
+declare void @dummy5()
+declare void @dummy6()
+declare void @dummy7()
+declare void @dummy8()
+declare void @dummy9()
+
+define void @external_external_1(i32 *%a) unnamed_addr {
+ call void @dummy1()
+ ret void
+}
+define void @external_external_2(float *%a) unnamed_addr {
+ call void @dummy1()
+ ret void
+}
+
+define void @external_internal_1(i32 *%a) unnamed_addr {
+ call void @dummy2()
+ ret void
+}
+define internal void @external_internal_2(float *%a) unnamed_addr {
+ call void @dummy2()
+ ret void
+}
+
+define internal void @internal_external_1(i32 *%a) unnamed_addr {
+ call void @dummy3()
+ ret void
+}
+define void @internal_external_2(float *%a) unnamed_addr {
+ call void @dummy3()
+ ret void
+}
+
+define weak void @weak_weak_1(i32 *%a) unnamed_addr {
+ call void @dummy4()
+ ret void
+}
+define weak void @weak_weak_2(float *%a) unnamed_addr {
+ call void @dummy4()
+ ret void
+}
+
+define weak void @weak_external_1(i32 *%a) unnamed_addr {
+ call void @dummy5()
+ ret void
+}
+define external void @weak_external_2(float *%a) unnamed_addr {
+ call void @dummy5()
+ ret void
+}
+
+define external void @external_weak_1(i32 *%a) unnamed_addr {
+ call void @dummy6()
+ ret void
+}
+define weak void @external_weak_2(float *%a) unnamed_addr {
+ call void @dummy6()
+ ret void
+}
+
+define weak void @weak_internal_1(i32 *%a) unnamed_addr {
+ call void @dummy7()
+ ret void
+}
+define internal void @weak_internal_2(float *%a) unnamed_addr {
+ call void @dummy7()
+ ret void
+}
+
+define internal void @internal_weak_1(i32 *%a) unnamed_addr {
+ call void @dummy8()
+ ret void
+}
+define weak void @internal_weak_2(float *%a) unnamed_addr {
+ call void @dummy8()
+ ret void
+}
+
+define internal void @internal_internal_1(i32 *%a) unnamed_addr {
+ call void @dummy9()
+ ret void
+}
+define internal void @internal_internal_2(float *%a) unnamed_addr {
+ call void @dummy9()
+ ret void
+}