dotnet · davidwrighton · May 15, 2025 · Apr 22, 2025 · Apr 22, 2025 · Apr 22, 2025
diff --git a/src/coreclr/inc/clrconfigvalues.h b/src/coreclr/inc/clrconfigvalues.h
@@ -254,6 +254,7 @@ CONFIG_DWORD_INFO(INTERNAL_FastGCCheckStack, W("FastGCCheckStack"), 0, "")
 CONFIG_DWORD_INFO(INTERNAL_FastGCStress, W("FastGCStress"), 0, "Reduce the number of GCs done by enabling GCStress")
 RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_GCBreakOnOOM, W("GCBreakOnOOM"), 0, "Does a DebugBreak at the soonest time we detect an OOM")
 RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_gcConcurrent, W("gcConcurrent"), (DWORD)-1, "Enables/Disables concurrent GC")
+RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_UseGCWriteBarrierCopy, W("UseGCWriteBarrierCopy"), 1, "Use a copy of the write barrier for the GC. This is somewhat faster and for optimizations where the barrier is mutated as the program runs. Setting this to 0 removes scenarios where the write barrier is ever mutable.")
 
 #ifdef FEATURE_CONSERVATIVE_GC
 RETAIL_CONFIG_DWORD_INFO(UNSUPPORTED_gcConservative, W("gcConservative"), 0, "Enables/Disables conservative GC")

diff --git a/src/coreclr/inc/jithelpers.h b/src/coreclr/inc/jithelpers.h
@@ -184,11 +184,11 @@
     JITHELPER(CORINFO_HELP_CHECK_OBJ,           JIT_CheckObj,       METHOD__NIL)
 
     // GC Write barrier support
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF,   JIT_WriteBarrier,   METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF, JIT_CheckedWriteBarrier,METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF,   RhpAssignRef,   METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF, RhpCheckedAssignRef,METHOD__NIL)
     JITHELPER(CORINFO_HELP_ASSIGN_REF_ENSURE_NONHEAP, JIT_WriteBarrierEnsureNonHeapTarget,METHOD__NIL)
 
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_BYREF, JIT_ByRefWriteBarrier,METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_BYREF, RhpByRefAssignRef,METHOD__NIL)
     DYNAMICJITHELPER(CORINFO_HELP_BULK_WRITEBARRIER, NULL, METHOD__BUFFER__MEMCOPYGC)
 
     // Accessing fields
@@ -286,19 +286,19 @@
 #endif // !FEATURE_EH_FUNCLETS
 
 #ifdef TARGET_X86
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EAX, JIT_WriteBarrierEAX, METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EBX, JIT_WriteBarrierEBX, METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_ECX, JIT_WriteBarrierECX, METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_ESI, JIT_WriteBarrierESI, METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EDI, JIT_WriteBarrierEDI, METHOD__NIL)
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EBP, JIT_WriteBarrierEBP, METHOD__NIL)
-
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EAX, JIT_CheckedWriteBarrierEAX, METHOD__NIL)
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EBX, JIT_CheckedWriteBarrierEBX, METHOD__NIL)
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_ECX, JIT_CheckedWriteBarrierECX, METHOD__NIL)
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_ESI, JIT_CheckedWriteBarrierESI, METHOD__NIL)
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EDI, JIT_CheckedWriteBarrierEDI, METHOD__NIL)
-    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EBP, JIT_CheckedWriteBarrierEBP, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EAX, RhpAssignRefEAX, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EBX, RhpAssignRefEBX, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_ECX, RhpAssignRefECX, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_ESI, RhpAssignRefESI, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EDI, RhpAssignRefEDI, METHOD__NIL)
+    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF_EBP, RhpAssignRefEBP, METHOD__NIL)
+
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EAX, RhpCheckedAssignRefEAX, METHOD__NIL)
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EBX, RhpCheckedAssignRefEBX, METHOD__NIL)
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_ECX, RhpCheckedAssignRefECX, METHOD__NIL)
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_ESI, RhpCheckedAssignRefESI, METHOD__NIL)
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EDI, RhpCheckedAssignRefEDI, METHOD__NIL)
+    JITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF_EBP, RhpCheckedAssignRefEBP, METHOD__NIL)
 #else
     JITHELPER(CORINFO_HELP_ASSIGN_REF_EAX, NULL, METHOD__NIL)
     JITHELPER(CORINFO_HELP_ASSIGN_REF_EBX, NULL, METHOD__NIL)

diff --git a/src/coreclr/jit/targetarm.h b/src/coreclr/jit/targetarm.h
@@ -138,7 +138,8 @@
   //     On exit:
   //       r0: trashed
   //       r3: trashed
-  // CORINFO_HELP_ASSIGN_BYREF (JIT_ByRefWriteBarrier):
+  //      r12: trashed
+// CORINFO_HELP_ASSIGN_BYREF (JIT_ByRefWriteBarrier):
   //     On entry:
   //       r0: the destination address (object reference written here)
   //       r1: the source address (points to object reference to write)
@@ -147,6 +148,7 @@
   //       r1: incremented by 4
   //       r2: trashed
   //       r3: trashed
+  //      r12: trashed
 
   #define REG_WRITE_BARRIER_DST          REG_ARG_0
   #define RBM_WRITE_BARRIER_DST          RBM_ARG_0

@@ -213,7 +213,7 @@ list(APPEND RUNTIME_SOURCES_ARCH_ASM
   ${ARCH_SOURCES_DIR}/InteropThunksHelpers.${ASM_SUFFIX}
   ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/StubDispatch.${ASM_SUFFIX}
   ${ARCH_SOURCES_DIR}/UniversalTransition.${ASM_SUFFIX}
-  ${ARCH_SOURCES_DIR}/WriteBarriers.${ASM_SUFFIX}
+  ${RUNTIME_DIR}/${ARCH_SOURCES_DIR}/WriteBarriers.${ASM_SUFFIX}
 )
 
 if (CLR_CMAKE_TARGET_ARCH_AMD64 OR CLR_CMAKE_TARGET_ARCH_ARM64)

@@ -0,0 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// This file is used to allow sharing of assembly code between NativeAOT and CoreCLR, which have different conventions about how to ensure that constants offsets are accessible
+
+#include "AsmOffsets.inc"
+#include <unixasmmacros.inc>
@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// This file is used to allow sharing of assembly code between NativeAOT and CoreCLR, which have different conventions about how to ensure that constants offsets are accessible
+
+// TODO: Implement
@@ -0,0 +1,6 @@
+; Licensed to the .NET Foundation under one or more agreements.
+; The .NET Foundation licenses this file to you under the MIT license.
+
+; This file is used to allow sharing of assembly code between NativeAOT and CoreCLR, which have different conventions about how to ensure that constants offsets are accessible
+
+include AsmMacros.inc
@@ -0,0 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// This file is used to allow sharing of assembly code between NativeAOT and CoreCLR, which have different conventions about how to ensure that constants offsets are accessible
+
+#include <unixasmmacros.inc>
+#include "AsmOffsets.inc"
@@ -0,0 +1,7 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// This file is used to allow sharing of assembly code between NativeAOT and CoreCLR, which have different conventions about how to ensure that constants offsets are accessible
+
+#include <unixasmmacros.inc>
+#include "AsmOffsets.inc"
diff --git a/src/coreclr/pal/inc/unixasmmacrosarm.inc b/src/coreclr/pal/inc/unixasmmacrosarm.inc
@@ -44,10 +44,28 @@ C_FUNC(\Name\()_End):
         nop
 .endm
 
+.macro GLOBAL_LABEL Name
+        .global C_FUNC(\Name)
+C_FUNC(\Name):
+.endm
+
+.macro ALTERNATE_ENTRY Name
+        .global C_FUNC(\Name)
+        .type \Name, %function
+C_FUNC(\Name):
+.endm
+
 .macro PREPARE_EXTERNAL_VAR Name, HelperReg
         ldr \HelperReg, [pc, #C_FUNC(\Name)@GOTPCREL]
 .endm
 
+.macro PREPARE_EXTERNAL_VAR_INDIRECT Name, HelperReg
+        movw \HelperReg, #:lower16:C_FUNC(\Name) - (. + 12)
+        movt \HelperReg, #:upper16:C_FUNC(\Name) - (. + 8)
+        add \HelperReg, pc
+        ldr \HelperReg, [\HelperReg]
+.endm
+
 .macro push_nonvol_reg Register
         push \Register
         .save \Register

diff --git a/src/coreclr/pal/inc/unixasmmacrosloongarch64.inc b/src/coreclr/pal/inc/unixasmmacrosloongarch64.inc
@@ -17,6 +17,12 @@
 C_FUNC(\Name):
 .endm
 
+.macro ALTERNATE_ENTRY Name
+        .global C_FUNC(\Name)
+        .hidden C_FUNC(\Name)
+C_FUNC(\Name):
+.endm
+
 .macro LEAF_ENTRY Name, Section
         .global C_FUNC(\Name)
         .type \Name, %function
@@ -41,6 +47,16 @@ C_FUNC(\Name\()_End):
     la.local  \HelperReg, \Name
 .endm
 
+.macro PREPARE_EXTERNAL_VAR_INDIRECT Name, HelperReg
+        la.local  \HelperReg, \Name
+        ld.d  \HelperReg, \HelperReg, 0
+.endm
+
+.macro PREPARE_EXTERNAL_VAR_INDIRECT_W Name, HelperReg
+        la.local  \HelperReg, \Name
+        ld.w  \HelperReg, \HelperReg, 0
+.endm
+
 .macro PROLOG_STACK_ALLOC Size
         addi.d $sp, $sp, -\Size
         //.cfi_adjust_cfa_offset \Size

diff --git a/src/coreclr/pal/inc/unixasmmacrosriscv64.inc b/src/coreclr/pal/inc/unixasmmacrosriscv64.inc
@@ -37,6 +37,12 @@ C_FUNC(\Name\()_End):
     nop
 .endm
 
+.macro ALTERNATE_ENTRY Name
+        .global C_FUNC(\Name)
+        .hidden C_FUNC(\Name)
+C_FUNC(\Name):
+.endm
+
 .macro PREPARE_EXTERNAL_VAR Name, HelperReg
     lla  \HelperReg, \Name
 .endm

diff --git a/src/coreclr/pal/inc/unixasmmacrosx86.inc b/src/coreclr/pal/inc/unixasmmacrosx86.inc
@@ -24,6 +24,12 @@ C_FUNC(\Name):
 C_FUNC(\Name):
 .endm
 
+.macro ALTERNATE_ENTRY Name
+        .global C_FUNC(\Name)
+        .type \Name, %function
+C_FUNC(\Name):
+.endm
+
 .macro LEAF_END Name, Section
         .size \Name, .-\Name
         .cfi_endproc

diff --git a/src/coreclr/runtime/amd64/StubDispatch.S b/src/coreclr/runtime/amd64/StubDispatch.S
@@ -6,6 +6,15 @@
 
 #ifdef FEATURE_CACHED_INTERFACE_DISPATCH
 
+#if defined(__APPLE__)
+    // Currently the build is failing without this due to an issue if the first method in the assembly file has an alternate entry at the start of the file.
+    // Fix, but adding an empty, unused method
+    LEAF_ENTRY RhpStubDispatchDoNotFailToBuild, _TEXT
+       ret
+    LEAF_END RhpStubDispatchDoNotFailToBuild, _TEXT
+#endif
+
+
 // trick to avoid PLT relocation at runtime which corrupts registers
 #define REL_C_FUNC(name) C_FUNC(name)@gotpcrel
 
@@ -20,7 +29,15 @@ LEAF_ENTRY RhpInterfaceDispatch\entries, _TEXT
         mov     r10, [r11 + OFFSETOF__InterfaceDispatchCell__m_pCache]
 
         // Load the MethodTable from the object instance in rdi.
+#ifdef TARGET_APPLE
+// Apple's linker has issues which break unwind info if
+// an ALTERNATE_ENTRY is present in the middle of a function see https://github.com/dotnet/runtime/pull/114982#discussion_r2083272768
+.cfi_endproc
+#endif
         ALTERNATE_ENTRY RhpInterfaceDispatchAVLocation\entries
+#ifdef TARGET_APPLE
+.cfi_startproc
+#endif
         mov     rax, [rdi]
 
         CurrentOffset = OFFSETOF__InterfaceDispatchCache__m_rgEntries

diff --git a/...r/nativeaot/Runtime/amd64/WriteBarriers.S → src/coreclr/runtime/amd64/WriteBarriers.S b/...r/nativeaot/Runtime/amd64/WriteBarriers.S → src/coreclr/runtime/amd64/WriteBarriers.S
@@ -2,7 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 .intel_syntax noprefix
-#include <unixasmmacros.inc>
+#include "AsmMacros_Shared.h"
+
+#if defined(__APPLE__)
+    // Currently the build is failing without this due to an issue if the first method in the assembly file has an alternate entry at the start of the file.
+    // Fix, but adding an empty, unused method
+    LEAF_ENTRY RhpWriteBarriersDoNotFailToBuild, _TEXT
+       ret
+    LEAF_END RhpWriteBarriersDoNotFailToBuild, _TEXT
+#endif
 
 #ifdef WRITE_BARRIER_CHECK
 
@@ -261,7 +269,15 @@ LEAF_END RhpCheckedXchg, _TEXT
 LEAF_ENTRY RhpByRefAssignRef, _TEXT
 ALTERNATE_ENTRY RhpByRefAssignRefAVLocation1
     mov     rcx, [rsi]
+#ifdef TARGET_APPLE
+// Apple's linker has issues which break unwind info if
 if (ip < funcStart || ip > funcEnd) { 
     ERROR("ip %p not in regular second level\n", (void*)ip); 
     return false; 
 } 
 if (ip < funcStart || ip > funcEnd) { 
     ERROR("ip %p not in compressed second level\n", (void*)ip); 
     return false; 
 } 
 if (ip < funcStart || ip > funcEnd) { 
     ERROR("ip %p not in regular second level\n", (void*)ip); 
     return false; 
 } 
 if (ip < funcStart || ip > funcEnd) { 
     ERROR("ip %p not in compressed second level\n", (void*)ip); 
     return false; 
 } 
+// an ALTERNATE_ENTRY is present in the middle of a function see https://github.com/dotnet/runtime/pull/114982#discussion_r2083272768
+.cfi_endproc
+#endif
 ALTERNATE_ENTRY RhpByRefAssignRefAVLocation2
+#ifdef TARGET_APPLE
+.cfi_startproc
+#endif
     mov     [rdi], rcx
 
     // Check whether the writes were even into the heap. If not there's no card update required.

diff --git a/...nativeaot/Runtime/amd64/WriteBarriers.asm → src/coreclr/runtime/amd64/WriteBarriers.asm b/...nativeaot/Runtime/amd64/WriteBarriers.asm → src/coreclr/runtime/amd64/WriteBarriers.asm
@@ -1,7 +1,7 @@
 ;; Licensed to the .NET Foundation under one or more agreements.
 ;; The .NET Foundation licenses this file to you under the MIT license.
 
-include AsmMacros.inc
+include AsmMacros_Shared.inc
 
 ;; Macro used to copy contents of newly updated GC heap locations to a shadow copy of the heap. This is used
 ;; during garbage collections to verify that object references where never written to the heap without using a

diff --git a/src/coreclr/runtime/arm/StubDispatch.S b/src/coreclr/runtime/arm/StubDispatch.S
@@ -4,8 +4,7 @@
 .syntax unified
 .thumb
 
-#include <AsmOffsets.inc>         // generated by the build from AsmOffsets.cpp
-#include <unixasmmacros.inc>
+#include "AsmMacros_Shared.h"
 
 #ifdef FEATURE_CACHED_INTERFACE_DISPATCH