[JITLink][AArch64] Add support for splitting eh-frames on AArch64.

This is needed for DWARF eh-frame exception handling on AArch64.

#52921.

Original patch by David Nadlinger <code@klickverbot.at> (thanks David!),
testcase and comments added by me.

llvm/lib/ExecutionEngine/JITLink/MachO_arm64.cpp

@@ -709,6 +709,13 @@ void link_MachO_arm64(std::unique_ptr<LinkGraph> G,
     Config.PrePrunePasses.push_back(
         CompactUnwindSplitter("__LD,__compact_unwind"));
 
+    // Add eh-frame passses.
+    // FIXME: Prune eh-frames for which compact-unwind is available once
+    // we support compact-unwind registration with libunwind.
+    Config.PrePrunePasses.push_back(EHFrameSplitter("__TEXT,__eh_frame"));
+    Config.PrePrunePasses.push_back(
+        EHFrameEdgeFixer("__TEXT,__eh_frame", 8, Delta64, Delta32, NegDelta32));
+
     // Add an in-place GOT/Stubs pass.
     Config.PostPrunePasses.push_back(
         PerGraphGOTAndPLTStubsBuilder_MachO_arm64::asPass);

llvm/test/ExecutionEngine/JITLink/AArch64/MachO_arm64_ehframe.s

@@ -0,0 +1,101 @@
+# REQUIRES: asserts
+# RUN: llvm-mc -triple=arm64-apple-darwin11 -filetype=obj -o %t %s
+# RUN: llvm-jitlink -noexec -debug-only=jitlink %t 2>&1 | FileCheck %s
+#
+# Check that splitting of eh-frame sections works.
+#
+# CHECK: EHFrameSplitter: Processing __TEXT,__eh_frame...
+# CHECK:  Processing block at
+# CHECK:    Processing CFI record at
+# CHECK:      Extracted {{.*}} section = __TEXT,__eh_frame
+# CHECK:    Processing CFI record at
+# CHECK:      Extracted {{.*}} section = __TEXT,__eh_frame
+# CHECK: EHFrameEdgeFixer: Processing __TEXT,__eh_frame...
+# CHECK:   Processing block at
+# CHECK:     Processing CFI record at
+# CHECK:       Record is CIE
+# CHECK:   Processing block at
+# CHECK:     Processing CFI record at
+# CHECK:       Record is FDE
+# CHECK:         Adding edge at {{.*}} to CIE at: {{.*}}
+# CHECK:         Already has edge at {{.*}} to PC at {{.*}}
+# CHECK:         Adding keep-alive edge from target at {{.*}} to FDE at {{.*}}
+# CHECK:         Already has edge at {{.*}} to LSDA at {{.*}}
+
+	.section	__TEXT,__text,regular,pure_instructions
+ 	.globl	_main
+	.p2align	2
+_main:
+Lfunc_begin0:
+	.cfi_startproc
+	.cfi_personality 155, ___gxx_personality_v0
+	.cfi_lsda 16, Lexception0
+
+	stp	x20, x19, [sp, #-32]!
+	stp	x29, x30, [sp, #16]
+	.cfi_def_cfa_offset 32
+	.cfi_offset w30, -8
+	.cfi_offset w29, -16
+	.cfi_offset w19, -24
+	.cfi_offset w20, -32
+	mov	w0, #4
+	bl	___cxa_allocate_exception
+	mov	w8, #42
+	str	w8, [x0]
+Ltmp0:
+Lloh0:
+	adrp	x1, __ZTIi@GOTPAGE
+Lloh1:
+	ldr	x1, [x1, __ZTIi@GOTPAGEOFF]
+	mov	x2, #0
+	bl	___cxa_throw
+Ltmp1:
+
+	brk	#0x1
+LBB0_2:
+Ltmp2:
+	bl	___cxa_begin_catch
+	ldr	w19, [x0]
+	bl	___cxa_end_catch
+	mov	x0, x19
+	ldp	x29, x30, [sp, #16]
+	ldp	x20, x19, [sp], #32
+	ret
+	.loh AdrpLdrGot	Lloh0, Lloh1
+Lfunc_end0:
+	.cfi_endproc
+	.section	__TEXT,__gcc_except_tab
+	.p2align	2
+GCC_except_table0:
+Lexception0:
+	.byte	255
+	.byte	155
+	.uleb128 Lttbase0-Lttbaseref0
+Lttbaseref0:
+	.byte	1
+	.uleb128 Lcst_end0-Lcst_begin0
+Lcst_begin0:
+	.uleb128 Lfunc_begin0-Lfunc_begin0
+	.uleb128 Ltmp0-Lfunc_begin0
+	.byte	0
+	.byte	0
+	.uleb128 Ltmp0-Lfunc_begin0
+	.uleb128 Ltmp1-Ltmp0
+	.uleb128 Ltmp2-Lfunc_begin0
+	.byte	1
+	.uleb128 Ltmp1-Lfunc_begin0
+	.uleb128 Lfunc_end0-Ltmp1
+	.byte	0
+	.byte	0
+Lcst_end0:
+	.byte	1
+
+	.byte	0
+	.p2align	2
+
+Ltmp3:
+	.long	__ZTIi@GOT-Ltmp3
+Lttbase0:
+	.p2align	2
+
+.subsections_via_symbols