[ORC][ORC-RT] Rewrite the MachO platform to use allocation actions.

This patch updates the MachO platform (both the ORC MachOPlatform class and the
ORC-Runtime macho_platform.* files) to use allocation actions, rather than EPC
calls, to transfer the initializer information scraped from each linked object.
Interactions between the ORC and ORC-Runtime sides of the platform are
substantially redesigned to accomodate the change.

The high-level changes in this patch are:

1. The MachOPlatform::setupJITDylib method now calls into the runtime to set up
   a dylib name <-> header mapping, and a dylib state object (JITDylibState).

2. The MachOPlatformPlugin builds an allocation action that calls the
   __orc_rt_macho_register_object_platform_sections and
   __orc_rt_macho_deregister_object_platform_sections functions in the runtime
   to register the address ranges for all "interesting" sections in the object
   being allocated (TLS data sections, initializers, language runtime metadata
   sections, etc.).

3. The MachOPlatform::rt_getInitializers method (the entry point in the
   controller for requests from the runtime for initializer information) is
   replaced by MachOPlatform::rt_pushInitializers. The former returned a data
   structure containing the "interesting" section address ranges, but these are
   now handled by __orc_rt_macho_register_object_platform_sections. The new
   rt_pushInitializers method first issues a lookup to trigger materialization
   of the "interesting" sections, then returns the dylib dependence tree rooted
   at the requested dylib for dlopen to consume. (The dylib dependence tree is
   returned by rt_pushInitializers, rather than being handled by some dedicated
   call, because rt_pushInitializers can alter the dependence tree).

The advantage of these changes (beyond the performance advantages of using
allocation actions) is that it moves more information about the materialized
portions of the JITDylib into the executor. This tends to make the runtime
easier to reason about, e.g. the implementation of dlopen in the runtime is now
recursive, rather than relying on recursive calls in the controller to build a
linear data structure for consumption by the runtime. This change can also make
some operations more efficient, e.g. JITDylibs can be dlclosed and then
re-dlopened without having to pull all initializers over from the controller
again.

In addition to the high-level changes, there are some low-level changes to ORC
and the runtime:

* In ORC, at ExecutionSession teardown time JITDylibs are now destroyed in
reverse creation order. This is on the assumption that the ORC runtime will be
loaded into an earlier dylib that will be used by later JITDylibs. This is a
short-term solution to crashes that arose during testing when the runtime was
torn down before its users. Longer term we will likely destroy dylibs in
dependence order.

* toSPSSerializable(Expected<T> E) is updated to explicitly initialize the T
value, allowing it to be used by Ts that have explicit constructors.

* The ORC runtime now (1) attempts to track ref-counts, and (2) distinguishes
not-yet-processed "interesting" sections from previously processed ones. (1)
is necessary for standard dlopen/dlclose emulation. (2) is intended as a step
towards better REPL support -- it should enable future runtime calls that
run only newly registered initializers ("dlopen_more", "dlopen_additions",
...?).

compiler-rt/lib/orc/macho_platform.h

@@ -31,28 +31,6 @@ ORC_RT_INTERFACE void *__orc_rt_macho_jit_dlsym(void *dso_handle,
 namespace __orc_rt {
 namespace macho {
 
-struct MachOJITDylibInitializers {
-  using SectionList = std::vector<ExecutorAddrRange>;
-
-  MachOJITDylibInitializers() = default;
-  MachOJITDylibInitializers(std::string Name, ExecutorAddr MachOHeaderAddress)
-      : Name(std::move(Name)),
-        MachOHeaderAddress(std::move(MachOHeaderAddress)) {}
-
-  std::string Name;
-  ExecutorAddr MachOHeaderAddress;
-  ExecutorAddr ObjCImageInfoAddress;
-
-  std::unordered_map<std::string, SectionList> InitSections;
-};
-
-class MachOJITDylibDeinitializers {};
-
-using MachOJITDylibInitializerSequence = std::vector<MachOJITDylibInitializers>;
-
-using MachOJITDylibDeinitializerSequence =
-    std::vector<MachOJITDylibDeinitializers>;
-
 enum dlopen_mode : int {
   ORC_RT_RTLD_LAZY = 0x1,
   ORC_RT_RTLD_NOW = 0x2,
@@ -61,43 +39,6 @@ enum dlopen_mode : int {
 };
 
 } // end namespace macho
-
-using SPSNamedExecutorAddrRangeSequenceMap =
-    SPSSequence<SPSTuple<SPSString, SPSExecutorAddrRangeSequence>>;
-
-using SPSMachOJITDylibInitializers =
-    SPSTuple<SPSString, SPSExecutorAddr, SPSExecutorAddr,
-             SPSNamedExecutorAddrRangeSequenceMap>;
-
-using SPSMachOJITDylibInitializerSequence =
-    SPSSequence<SPSMachOJITDylibInitializers>;
-
-/// Serialization traits for MachOJITDylibInitializers.
-template <>
-class SPSSerializationTraits<SPSMachOJITDylibInitializers,
-                             macho::MachOJITDylibInitializers> {
-public:
-  static size_t size(const macho::MachOJITDylibInitializers &MOJDIs) {
-    return SPSMachOJITDylibInitializers::AsArgList::size(
-        MOJDIs.Name, MOJDIs.MachOHeaderAddress, MOJDIs.ObjCImageInfoAddress,
-        MOJDIs.InitSections);
-  }
-
-  static bool serialize(SPSOutputBuffer &OB,
-                        const macho::MachOJITDylibInitializers &MOJDIs) {
-    return SPSMachOJITDylibInitializers::AsArgList::serialize(
-        OB, MOJDIs.Name, MOJDIs.MachOHeaderAddress, MOJDIs.ObjCImageInfoAddress,
-        MOJDIs.InitSections);
-  }
-
-  static bool deserialize(SPSInputBuffer &IB,
-                          macho::MachOJITDylibInitializers &MOJDIs) {
-    return SPSMachOJITDylibInitializers::AsArgList::deserialize(
-        IB, MOJDIs.Name, MOJDIs.MachOHeaderAddress, MOJDIs.ObjCImageInfoAddress,
-        MOJDIs.InitSections);
-  }
-};
-
 } // end namespace __orc_rt
 
 #endif // ORC_RT_MACHO_PLATFORM_H

compiler-rt/test/orc/TestCases/Darwin/x86-64/Inputs/standalone-ctor-and-cxa-atexit-dtor.S

@@ -0,0 +1,41 @@
+// Contains a static initializer and deinitializer registered with
+//  ___cxa_atexit. dlopen-ing/dlclose-ing will print "constructor" and
+// "destructor" respectively.
+
+	.section	__TEXT,__text,regular,pure_instructions
+	.build_version macos, 12, 0	sdk_version 12, 0, 1
+	.globl	_deinitializer
+	.p2align	4, 0x90
+_deinitializer:
+	pushq	%rbp
+	movq	%rsp, %rbp
+	leaq	L_str.2(%rip), %rdi
+	popq	%rbp
+	jmp	_puts
+
+	.section	__TEXT,__StaticInit,regular,pure_instructions
+	.p2align	4, 0x90
+_initializer:
+	pushq	%rbp
+	movq	%rsp, %rbp
+	leaq	L_str(%rip), %rdi
+	callq	_puts
+	movq	_deinitializer@GOTPCREL(%rip), %rdi
+	leaq	_I(%rip), %rsi
+	leaq	___dso_handle(%rip), %rdx
+	popq	%rbp
+	jmp	___cxa_atexit
+
+	.globl	_I
+.zerofill __DATA,__common,_I,1,0
+	.section	__DATA,__mod_init_func,mod_init_funcs
+	.p2align	3
+	.quad	_initializer
+	.section	__TEXT,__cstring,cstring_literals
+L_str:
+	.asciz	"constructor"
+
+L_str.2:
+	.asciz	"destructor"
+
+.subsections_via_symbols

compiler-rt/test/orc/TestCases/Darwin/x86-64/trivial-jit-dlopen.S

@@ -0,0 +1,119 @@
+// Test that __orc_rt_macho_jit_dlopen and __orc_rt_macho_jit_dlclose run
+// constructors and destructors as expected.
+//
+// This test calls dlopen and dlclose twice. We expect the inner calls to be
+// no-ops.
+//
+// RUN: %clang -c -o %t.inits.o %p/Inputs/standalone-ctor-and-cxa-atexit-dtor.S
+// RUN: %clang -c -o %t.test.o %s
+// RUN: %llvm_jitlink \
+// RUN:   -alias _dlopen=___orc_rt_macho_jit_dlopen \
+// RUN:   -alias _dlclose=___orc_rt_macho_jit_dlclose \
+// RUN:   %t.test.o -jd inits %t.inits.o -lmain | FileCheck %s
+//
+// CHECK: entering main
+// CHECK-NEXT: first dlopen
+// CHECK-NEXT: constructor
+// CHECK-NEXT: second dlopen
+// CHECK-NEXT: first dlclose
+// CHECK-NEXT: second dlclose
+// CHECK-NEXT: destructor
+// CHECK-NEXT: leaving main
+
+	.section	__TEXT,__text,regular,pure_instructions
+	.build_version macos, 12, 0	sdk_version 13, 0
+	.globl	_main
+	.p2align	4, 0x90
+_main:
+
+	pushq	%rbp
+	movq	%rsp, %rbp
+	pushq	%r15
+	pushq	%r14
+	pushq	%rbx
+	pushq	%rax
+	leaq	L_str(%rip), %rdi
+	callq	_puts
+	leaq	L_str.9(%rip), %rdi
+	callq	_puts
+	leaq	L_.str.2(%rip), %rdi
+	movl	$1, %esi
+	callq	_dlopen
+	movl	$-1, %r14d
+	leaq	L_str.17(%rip), %r15
+	testq	%rax, %rax
+	je	LBB0_6
+
+	movq	%rax, %rbx
+	leaq	L_str.11(%rip), %rdi
+	callq	_puts
+	leaq	L_.str.2(%rip), %rdi
+	movl	$1, %esi
+	callq	_dlopen
+	testq	%rax, %rax
+	je	LBB0_6
+
+	cmpq	%rbx, %rax
+	je	LBB0_4
+
+	leaq	L_str.18(%rip), %r15
+	jmp	LBB0_6
+LBB0_4:
+	leaq	L_str.13(%rip), %rdi
+	callq	_puts
+	movq	%rbx, %rdi
+	callq	_dlclose
+	cmpl	$-1, %eax
+	je	LBB0_6
+
+	leaq	L_str.14(%rip), %rdi
+	callq	_puts
+	movq	%rbx, %rdi
+	callq	_dlclose
+	xorl	%r14d, %r14d
+	cmpl	$-1, %eax
+	sete	%r14b
+	leaq	L_str.17(%rip), %rax
+	leaq	L_str.15(%rip), %r15
+	cmoveq	%rax, %r15
+	negl	%r14d
+LBB0_6:
+	movq	%r15, %rdi
+	callq	_puts
+	movl	%r14d, %eax
+	addq	$8, %rsp
+	popq	%rbx
+	popq	%r14
+	popq	%r15
+	popq	%rbp
+	retq
+
+	.section	__TEXT,__cstring,cstring_literals
+L_.str.2:
+	.asciz	"inits"
+
+L_str:
+	.asciz	"entering main"
+
+L_str.9:
+	.asciz	"first dlopen"
+
+L_str.11:
+	.asciz	"second dlopen"
+
+L_str.13:
+	.asciz	"first dlclose"
+
+L_str.14:
+	.asciz	"second dlclose"
+
+L_str.15:
+	.asciz	"leaving main"
+
+L_str.17:
+	.asciz	"failed"
+
+L_str.18:
+	.asciz	"handles do not match"
+
+.subsections_via_symbols

compiler-rt/test/orc/lit.cfg.py

@@ -29,5 +29,8 @@ def build_invocation(compile_flags):
 # Default test suffixes.
 config.suffixes = ['.c', '.cpp', '.S']
 
+# Exclude Inputs directories.
+config.excludes = ['Inputs']
+
 if config.host_os not in ['Darwin', 'FreeBSD', 'Linux']:
   config.unsupported = True