Bring r254336 back:

The difference is that now we don't error on out-of-comdat access to
internal global values. We copy them instead. This seems to match the
expectation of COFF linkers (see pr25686).

Original message:

    Start deciding earlier what to link.

    A traditional linker is roughly split in symbol resolution and
"copying
    stuff".

    The two tasks are badly mixed in lib/Linker.

    This starts splitting them apart.

    With this patch there are no direct call to linkGlobalValueBody or
    linkGlobalValueProto. Everything is linked via WapValue.

    This also includes a few fixes:
    * A GV goes undefined if the comdat is dropped (comdat11.ll).
    * We error if an internal GV goes undefined (comdat13.ll).
    * We don't link an unused comdat.

    The first two match the behavior of an ELF linker. The second one is
    equivalent to running globaldce on the input.

llvm-svn: 254418

6 files changed, 72 insertions, 0 deletions

diff --git a/llvm/test/Linker/Inputs/comdat11.ll b/llvm/test/Linker/Inputs/comdat11.ll
new file mode 100644
index 00000000000..5b7f74cf0b2
--- /dev/null
+++ b/llvm/test/Linker/Inputs/comdat11.ll
@@ -0,0 +1,9 @@
+$foo = comdat any
+@foo = global i8 1, comdat
+define void @zed() {
+  call void @bar()
+  ret void
+}
+define void @bar() comdat($foo) {
+  ret void
+}
diff --git a/llvm/test/Linker/Inputs/comdat13.ll b/llvm/test/Linker/Inputs/comdat13.ll
new file mode 100644
index 00000000000..85515210ed7
--- /dev/null
+++ b/llvm/test/Linker/Inputs/comdat13.ll
@@ -0,0 +1,9 @@
+$foo = comdat any
+@foo = internal global i8 1, comdat
+define i8* @zed() {
+  call void @bax()
+  ret i8* @foo
+}
+define internal void @bax() comdat($foo) {
+  ret void
+}
diff --git a/llvm/test/Linker/comdat11.ll b/llvm/test/Linker/comdat11.ll
new file mode 100644
index 00000000000..dbade4104fe
--- /dev/null
+++ b/llvm/test/Linker/comdat11.ll
@@ -0,0 +1,13 @@
+; RUN: llvm-link -S %s %p/Inputs/comdat11.ll -o - | FileCheck %s
+
+$foo = comdat any
+@foo = global i8 0, comdat
+
+; CHECK: @foo = global i8 0, comdat
+
+; CHECK: define void @zed() {
+; CHECK:   call void @bar()
+; CHECK:   ret void
+; CHECK: }
+
+; CHECK: declare void @bar()
diff --git a/llvm/test/Linker/comdat12.ll b/llvm/test/Linker/comdat12.ll
new file mode 100644
index 00000000000..d06e222b63a
--- /dev/null
+++ b/llvm/test/Linker/comdat12.ll
@@ -0,0 +1,8 @@
+; RUN: llvm-link %s -S -o - | FileCheck %s
+
+$foo = comdat largest
+define internal void @foo() comdat($foo) {
+  ret void
+}
+
+; CHECK-NOT: foo
diff --git a/llvm/test/Linker/comdat13.ll b/llvm/test/Linker/comdat13.ll
new file mode 100644
index 00000000000..d1e382a2f27
--- /dev/null
+++ b/llvm/test/Linker/comdat13.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-link -S %s %p/Inputs/comdat13.ll -o - | FileCheck %s
+
+; In Inputs/comdat13.ll a function not in the $foo comdat (zed) references an
+; internal function in the comdat $foo.
+; The IR would be ilegal on ELF ("relocation refers to discarded section"),
+; but COFF linkers seem to just duplicate the comdat.
+
+$foo = comdat any
+@foo = internal global i8 0, comdat
+define i8* @bar() {
+       ret i8* @foo
+}
+
+; CHECK: $foo = comdat any
+
+; CHECK: @foo = internal global i8 0, comdat
+; CHECK: @foo.1 = internal global i8 1, comdat($foo)
+
+; CHECK:      define i8* @bar() {
+; CHECK-NEXT:   ret i8* @foo
+; CHECK-NEXT: }
+
+; CHECK:      define i8* @zed() {
+; CHECK-NEXT:   call void @bax()
+; CHECK-NEXT:   ret i8* @foo.1
+; CHECK-NEXT: }
+
+; CHECK:      define internal void @bax() comdat($foo) {
+; CHECK-NEXT:   ret void
+; CHECK-NEXT: }
diff --git a/llvm/test/Linker/comdat9.ll b/llvm/test/Linker/comdat9.ll
index 274957401aa..4f6f2cfb845 100644
--- a/llvm/test/Linker/comdat9.ll
+++ b/llvm/test/Linker/comdat9.ll
@@ -14,6 +14,9 @@ $f2 = comdat largest
 define internal void @f2() comdat($f2) {
   ret void
 }
+define void @f3() comdat($f2) {
+  ret void
+}
 
 ; CHECK-DAG: $f2 = comdat largest
 ; CHECK-DAG: define internal void @f2() comdat {