[WebAssembly] Implement @llvm.global_ctors and @llvm.global_dtors

Summary:
- lowers @llvm.global_dtors by adding @llvm.global_ctors
  functions which register the destructors with `__cxa_atexit`.
- impements @llvm.global_ctors with wasm start functions and linker metadata

See [here](https://github.com/WebAssembly/tool-conventions/issues/25) for more background.

Subscribers: jfb, dschuff, mgorny, jgravelle-google, aheejin, sunfish

Differential Revision: https://reviews.llvm.org/D41211

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@320774 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 139 insertions, 0 deletions

diff --git a/test/CodeGen/WebAssembly/lower-global-dtors.ll b/test/CodeGen/WebAssembly/lower-global-dtors.ll
new file mode 100644
index 00000000000..c3d654091a1
--- /dev/null
+++ b/test/CodeGen/WebAssembly/lower-global-dtors.ll
@@ -0,0 +1,139 @@
+; RUN: llc < %s -asm-verbose=false | FileCheck --check-prefix=CHECK --check-prefix=FINI --check-prefix=NULL %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-n32:64-S128"
+target triple = "wasm32-unknown-unknown-wasm"
+
+; Test that @llvm.global_dtors is properly lowered into @llvm.global_ctors,
+; grouping dtor calls by priority and associated symbol.
+
+declare void @orig_ctor()
+declare void @orig_dtor0()
+declare void @orig_dtor1a()
+declare void @orig_dtor1b()
+declare void @orig_dtor1c0()
+declare void @orig_dtor1c1a()
+declare void @orig_dtor1c1b()
+declare void @orig_dtor65536()
+declare void @after_the_null()
+
+@associated1c0 = external global i8
+@associated1c1 = external global i8
+
+@llvm.global_ctors = appending global
+[1 x { i32, void ()*, i8* }]
+[
+  { i32, void ()*, i8* } { i32 200, void ()* @orig_ctor, i8* null }
+]
+
+@llvm.global_dtors = appending global
+[9 x { i32, void ()*, i8* }]
+[
+  { i32, void ()*, i8* } { i32 0, void ()* @orig_dtor0, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1a, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1b, i8* null },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c0, i8* @associated1c0 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c1a, i8* @associated1c1 },
+  { i32, void ()*, i8* } { i32 1, void ()* @orig_dtor1c1b, i8* @associated1c1 },
+  { i32, void ()*, i8* } { i32 65535, void ()* @orig_dtor65536, i8* null },
+  { i32, void ()*, i8* } { i32 65535, void ()* null, i8* null },
+  { i32, void ()*, i8* } { i32 65535, void ()* @after_the_null, i8* null }
+]
+
+; CHECK-LABEL: .Lcall_dtors.0:
+; CHECK-NEXT: .param          i32{{$}}
+; CHECK-NEXT: call            orig_dtor0@FUNCTION{{$}}
+
+; CHECK-LABEL: .Lregister_call_dtors.0:
+; CHECK-NEXT: block
+; CHECK-NEXT: i32.const       $push2=, .Lcall_dtors.0@FUNCTION{{$}}
+; CHECK-NEXT: i32.const       $push1=, 0
+; CHECK-NEXT: i32.const       $push0=, __dso_handle
+; CHECK-NEXT: i32.call        $push3=, __cxa_atexit@FUNCTION, $pop2, $pop1, $pop0{{$}}
+; CHECK-NEXT: br_if           0, $pop3
+; CHECK-NEXT: return
+;      CHECK: end_block
+; CHECK-NEXT: unreachable
+
+; CHECK-LABEL: .Lcall_dtors.1:
+; CHECK-NEXT: .param          i32{{$}}
+; CHECK-NEXT: call            orig_dtor1a@FUNCTION{{$}}
+; CHECK-NEXT: call            orig_dtor1b@FUNCTION{{$}}
+
+; CHECK-LABEL: .Lregister_call_dtors.1:
+; CHECK-NEXT: block
+; CHECK-NEXT: i32.const       $push2=, .Lcall_dtors.1@FUNCTION{{$}}
+; CHECK-NEXT: i32.const       $push1=, 0
+; CHECK-NEXT: i32.const       $push0=, __dso_handle
+; CHECK-NEXT: i32.call        $push3=, __cxa_atexit@FUNCTION, $pop2, $pop1, $pop0{{$}}
+; CHECK-NEXT: br_if           0, $pop3
+; CHECK-NEXT: return
+;      CHECK: end_block
+; CHECK-NEXT: unreachable
+
+; CHECK-LABEL: .Lcall_dtors.1.associated1c0:
+; CHECK-NEXT: .param          i32{{$}}
+; CHECK-NEXT: call            orig_dtor1c0@FUNCTION{{$}}
+
+; CHECK-LABEL: .Lregister_call_dtors.1.associated1c0:
+; CHECK-NEXT: block
+; CHECK-NEXT: i32.const       $push2=, .Lcall_dtors.1.associated1c0@FUNCTION{{$}}
+; CHECK-NEXT: i32.const       $push1=, 0
+; CHECK-NEXT: i32.const       $push0=, __dso_handle
+; CHECK-NEXT: i32.call        $push3=, __cxa_atexit@FUNCTION, $pop2, $pop1, $pop0{{$}}
+; CHECK-NEXT: br_if           0, $pop3
+; CHECK-NEXT: return
+;      CHECK: end_block
+; CHECK-NEXT: unreachable
+
+; CHECK-LABEL: .Lcall_dtors.1.associated1c1:
+; CHECK-NEXT: .param          i32{{$}}
+; CHECK-NEXT: call            orig_dtor1c1a@FUNCTION{{$}}
+; CHECK-NEXT: call            orig_dtor1c1b@FUNCTION{{$}}
+
+; CHECK-LABEL: .Lregister_call_dtors.1.associated1c1:
+; CHECK-NEXT: block
+; CHECK-NEXT: i32.const       $push2=, .Lcall_dtors.1.associated1c1@FUNCTION{{$}}
+; CHECK-NEXT: i32.const       $push1=, 0
+; CHECK-NEXT: i32.const       $push0=, __dso_handle
+; CHECK-NEXT: i32.call        $push3=, __cxa_atexit@FUNCTION, $pop2, $pop1, $pop0{{$}}
+; CHECK-NEXT: br_if           0, $pop3
+; CHECK-NEXT: return
+;      CHECK: end_block
+; CHECK-NEXT: unreachable
+
+; CHECK-LABEL: .Lcall_dtors:
+; CHECK-NEXT: .param          i32{{$}}
+; CHECK-NEXT: call            orig_dtor65536@FUNCTION{{$}}
+
+; CHECK-LABEL: .Lregister_call_dtors:
+; CHECK-NEXT: block
+; CHECK-NEXT: i32.const       $push2=, .Lcall_dtors@FUNCTION{{$}}
+; CHECK-NEXT: i32.const       $push1=, 0
+; CHECK-NEXT: i32.const       $push0=, __dso_handle
+; CHECK-NEXT: i32.call        $push3=, __cxa_atexit@FUNCTION, $pop2, $pop1, $pop0{{$}}
+; CHECK-NEXT: br_if           0, $pop3
+; CHECK-NEXT: return
+;      CHECK: end_block
+; CHECK-NEXT: unreachable
+
+; CHECK-LABEL: .section .init_array.0,"",@
+;      CHECK: .int32  .Lregister_call_dtors.0@FUNCTION{{$}}
+; CHECK-LABEL: .section .init_array.1,"",@
+;      CHECK: .int32  .Lregister_call_dtors.1@FUNCTION{{$}}
+; CHECK-LABEL: .section .init_array.200,"",@
+;      CHECK: .int32  orig_ctor@FUNCTION{{$}}
+; CHECK-LABEL: .section .init_array,"",@
+;      CHECK: .int32  .Lregister_call_dtors@FUNCTION{{$}}
+
+; CHECK-LABEL: .weak __dso_handle
+
+; CHECK-LABEL: .functype __cxa_atexit, i32, i32, i32, i32{{$}}
+
+; We shouldn't make use of a .fini_array section.
+
+; FINI-NOT: fini_array
+
+; This function is listed after the null terminator, so it should
+; be excluded.
+
+; NULL-NOT: after_the_null