Remove CORINFO_HELP_ASSIGN_BYREF and related dead code

docs/design/coreclr/botr/readytorun-format.md

@@ -894,7 +894,7 @@ enum ReadyToRunHelper
     // Write barriers
     READYTORUN_HELPER_WriteBarrier              = 0x30,
     READYTORUN_HELPER_CheckedWriteBarrier       = 0x31,
-    READYTORUN_HELPER_ByRefWriteBarrier         = 0x32,
+    READYTORUN_HELPER_ByRefWriteBarrier         = 0x32, // Unused since READYTORUN_MAJOR_VERSION 19.0
 
     // Array helpers
     READYTORUN_HELPER_Stelem_Ref                = 0x38,

src/coreclr/inc/corinfo.h

@@ -430,7 +430,6 @@ enum CorInfoHelpFunc
     CORINFO_HELP_ASSIGN_REF,        // universal helpers with F_CALL_CONV calling convention
     CORINFO_HELP_CHECKED_ASSIGN_REF,
 
-    CORINFO_HELP_ASSIGN_BYREF,
     CORINFO_HELP_BULK_WRITEBARRIER,
 
     /* Accessing fields */

src/coreclr/inc/jiteeversionguid.h

@@ -37,11 +37,11 @@
 
 #include <minipal/guid.h>
 
-constexpr GUID JITEEVersionIdentifier = { /* fc5f63e7-921b-4091-b920-8df8d7b872c1 */
-    0xfc5f63e7,
-    0x921b,
-    0x4091,
-    {0xb9, 0x20, 0x8d, 0xf8, 0xd7, 0xb8, 0x72, 0xc1}
+constexpr GUID JITEEVersionIdentifier = { /* 31a04b06-915e-42a0-bbd2-c9c397677ae5 */
+    0x31a04b06,
+    0x915e,
+    0x42a0,
+    {0xbb, 0xd2, 0xc9, 0xc3, 0x97, 0x67, 0x7a, 0xe5}
   };
 
 #endif // JIT_EE_VERSIONING_GUID_H

src/coreclr/inc/jithelpers.h

@@ -170,12 +170,6 @@
     DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_REF,   RhpAssignRef,   METHOD__NIL)
     DYNAMICJITHELPER(CORINFO_HELP_CHECKED_ASSIGN_REF, RhpCheckedAssignRef,METHOD__NIL)
 
-#ifdef TARGET_WASM
-    JITHELPER(CORINFO_HELP_ASSIGN_BYREF, NULL, METHOD__NIL)
-#else
-    DYNAMICJITHELPER(CORINFO_HELP_ASSIGN_BYREF, RhpByRefAssignRef,METHOD__NIL)
-#endif // TARGET_WASM
-
     DYNAMICJITHELPER(CORINFO_HELP_BULK_WRITEBARRIER, NULL, METHOD__BUFFER__MEMCOPYGC)
 
     // Accessing fields

src/coreclr/inc/readytorun.h

@@ -19,10 +19,10 @@
 //  src/coreclr/nativeaot/Runtime/inc/ModuleHeaders.h
 // If you update this, ensure you run `git grep MINIMUM_READYTORUN_MAJOR_VERSION`
 // and handle pending work.
-#define READYTORUN_MAJOR_VERSION 18
-#define READYTORUN_MINOR_VERSION 0x0007
+#define READYTORUN_MAJOR_VERSION 19
+#define READYTORUN_MINOR_VERSION 0x0000
 
-#define MINIMUM_READYTORUN_MAJOR_VERSION 18
+#define MINIMUM_READYTORUN_MAJOR_VERSION 19
 
 // R2R Version 2.1 adds the InliningInfo section
 // R2R Version 2.2 adds the ProfileDataInfo section
@@ -58,6 +58,7 @@
 // R2R Version 18.5 adds READYTORUN_FLAG_STRIPPED_IL_BODIES, READYTORUN_FLAG_STRIPPED_INLINING_INFO, and READYTORUN_FLAG_STRIPPED_DEBUG_INFO flags
 // R2R Version 18.6 adds READYTORUN_FIXUP_InjectStringThunks for mapping strings to pregenerated code thunks
 // R2R Version 18.7 adds READYTORUN_HELPER_R2RToInterpreter
+// R2R Version 19 removes the READYTORUN_HELPER_ByRefWriteBarrier helper
 
 struct READYTORUN_CORE_HEADER
 {
@@ -363,7 +364,7 @@ enum ReadyToRunHelper
     // Write barriers
     READYTORUN_HELPER_WriteBarrier              = 0x30,
     READYTORUN_HELPER_CheckedWriteBarrier       = 0x31,
-    READYTORUN_HELPER_ByRefWriteBarrier         = 0x32,
+    READYTORUN_HELPER_ByRefWriteBarrier         = 0x32, // No longer supported as of READYTORUN_MAJOR_VERSION 19.0
     READYTORUN_HELPER_BulkWriteBarrier          = 0x33,
 
     // Array helpers

src/coreclr/inc/readytorunhelpers.h

@@ -28,7 +28,6 @@ HELPER(READYTORUN_HELPER_ThrowNotImplemented,       CORINFO_HELP_THROW_NOT_IMPLE
 
 HELPER(READYTORUN_HELPER_WriteBarrier,              CORINFO_HELP_ASSIGN_REF,                        )
 HELPER(READYTORUN_HELPER_CheckedWriteBarrier,       CORINFO_HELP_CHECKED_ASSIGN_REF,                )
-HELPER(READYTORUN_HELPER_ByRefWriteBarrier,         CORINFO_HELP_ASSIGN_BYREF,                      )
 HELPER(READYTORUN_HELPER_BulkWriteBarrier,          CORINFO_HELP_BULK_WRITEBARRIER,                 )
 
 HELPER(READYTORUN_HELPER_Stelem_Ref,                CORINFO_HELP_ARRADDR_ST,                        )

src/coreclr/jit/codegenwasm.cpp

@@ -3222,8 +3222,6 @@ void CodeGen::genCodeForStoreBlk(GenTreeBlk* blkOp)
             emit->emitIns_I(INS_local_get, EA_PTRSIZE, WasmRegToIndex(destReg));
             emit->emitIns_I(INS_I_const, EA_PTRSIZE, destOffset);
             emit->emitIns(INS_I_add);
-            // Do an I_load here instead of I_const + I_add because we're using the (Object **, Object *) write barrier,
-            //  not the (Object **, Object **) BYREF write barrier used on other architectures.
             emit->emitIns_I(INS_local_get, EA_PTRSIZE, WasmRegToIndex(srcReg));
             emit->emitIns_I(INS_I_load, EA_PTRSIZE, srcOffset);
             // NOTE: This helper's signature omits SP/PEP so all we need on the stack is dst and ref.

src/coreclr/jit/targetarm64.h

@@ -159,7 +159,7 @@
 //       x15: the object reference to be stored
 //     On exit:
 //       x12: trashed
-//       x14: incremented by 8
+//       x14: preserved (the destination address is not modified)
 //       x15: trashed
 //       x17: trashed (ip1) if FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP
 //
@@ -175,7 +175,8 @@
 #define RBM_CALLEE_TRASH_NOGC          (RBM_R12|RBM_R15|RBM_IP0|RBM_IP1|RBM_DEFAULT_HELPER_CALL_TARGET)
 
 // Registers killed by CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
-#define RBM_CALLEE_TRASH_WRITEBARRIER         (RBM_R14|RBM_CALLEE_TRASH_NOGC)
+// Note: the destination register (x14) is preserved by the helper, so it is not in the kill set.
+#define RBM_CALLEE_TRASH_WRITEBARRIER         RBM_CALLEE_TRASH_NOGC
 
 // Registers no longer containing GC pointers after CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
 #define RBM_CALLEE_GCTRASH_WRITEBARRIER       RBM_CALLEE_TRASH_NOGC

src/coreclr/jit/targetloongarch64.h

@@ -143,7 +143,7 @@
 //       t1: trashed
 //       t3: trashed
 //       t4: trashed
-//       t6: incremented by 8
+//       t6: preserved (the destination address is not modified)
 //       t7: trashed
 //
 
@@ -156,7 +156,8 @@
 #define RBM_CALLEE_TRASH_NOGC          (RBM_T0|RBM_T1|RBM_T3|RBM_T4|RBM_T7|RBM_DEFAULT_HELPER_CALL_TARGET)
 
 // Registers killed by CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
-#define RBM_CALLEE_TRASH_WRITEBARRIER         (RBM_WRITE_BARRIER_DST|RBM_CALLEE_TRASH_NOGC)
+// Note: the destination register (t6) is preserved by the helper, so it is not in the kill set.
+#define RBM_CALLEE_TRASH_WRITEBARRIER         RBM_CALLEE_TRASH_NOGC
 
 // Registers no longer containing GC pointers after CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
 #define RBM_CALLEE_GCTRASH_WRITEBARRIER       RBM_CALLEE_TRASH_NOGC

src/coreclr/jit/targetriscv64.h

@@ -129,6 +129,19 @@
 #define REG_JUMP_THUNK_PARAM     REG_T2
 #define RBM_JUMP_THUNK_PARAM     RBM_T2
 
+// RISCV64 write barrier ABI (see vm/riscv64/asmhelpers.S):
+// CORINFO_HELP_ASSIGN_REF (JIT_WriteBarrier), CORINFO_HELP_CHECKED_ASSIGN_REF (JIT_CheckedWriteBarrier):
+//     On entry:
+//       t3: the destination address of the store
+//       t4: the object reference to be stored
+//     On exit:
+//       t0: trashed
+//       t1: trashed
+//       t3: preserved (the destination address is not modified)
+//       t4: trashed
+//       t6: trashed
+//
+
 #define REG_WRITE_BARRIER_DST          REG_T3
 #define RBM_WRITE_BARRIER_DST          RBM_T3
 
@@ -138,7 +151,8 @@
 #define RBM_CALLEE_TRASH_NOGC          (RBM_T0|RBM_T1|RBM_T2|RBM_T4|RBM_T6|RBM_DEFAULT_HELPER_CALL_TARGET)
 
 // Registers killed by CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
-#define RBM_CALLEE_TRASH_WRITEBARRIER         (RBM_WRITE_BARRIER_DST|RBM_CALLEE_TRASH_NOGC)
+// Note: the destination register (t3) is preserved by the helper, so it is not in the kill set.
+#define RBM_CALLEE_TRASH_WRITEBARRIER         RBM_CALLEE_TRASH_NOGC
 
 // Registers no longer containing GC pointers after CORINFO_HELP_ASSIGN_REF and CORINFO_HELP_CHECKED_ASSIGN_REF.
 #define RBM_CALLEE_GCTRASH_WRITEBARRIER       RBM_CALLEE_TRASH_NOGC

src/coreclr/nativeaot/Runtime/EHHelpers.cpp

@@ -219,11 +219,6 @@ EXTERN_C CODE_LOCATION RhpCheckedAssignRefESIAVLocation;
 EXTERN_C CODE_LOCATION RhpCheckedAssignRefEDIAVLocation;
 EXTERN_C CODE_LOCATION RhpCheckedAssignRefEBPAVLocation;
 #endif
-EXTERN_C CODE_LOCATION RhpByRefAssignRefAVLocation1;
-
-#if !defined(HOST_ARM64) && !defined(HOST_LOONGARCH64) && !defined(HOST_RISCV64)
-EXTERN_C CODE_LOCATION RhpByRefAssignRefAVLocation2;
-#endif
 
 #if defined(HOST_ARM64) && !defined(LSE_INSTRUCTIONS_ENABLED_BY_DEFAULT)
 EXTERN_C CODE_LOCATION RhpCheckedLockCmpXchgAVLocation2;
@@ -252,10 +247,6 @@ static bool InWriteBarrierHelper(uintptr_t faultingIP)
         (uintptr_t)&RhpCheckedAssignRefESIAVLocation,
         (uintptr_t)&RhpCheckedAssignRefEDIAVLocation,
         (uintptr_t)&RhpCheckedAssignRefEBPAVLocation,
-#endif
-        (uintptr_t)&RhpByRefAssignRefAVLocation1,
-#if !defined(HOST_ARM64) && !defined(HOST_LOONGARCH64) && !defined(HOST_RISCV64)
-        (uintptr_t)&RhpByRefAssignRefAVLocation2,
 #endif
     };
 

src/coreclr/nativeaot/Runtime/inc/ModuleHeaders.h

@@ -11,8 +11,8 @@ struct ReadyToRunHeaderConstants
 {
     static const uint32_t Signature = 0x00525452; // 'RTR'
 
-    static const uint32_t CurrentMajorVersion = 18;
-    static const uint32_t CurrentMinorVersion = 7;
+    static const uint32_t CurrentMajorVersion = 19;
+    static const uint32_t CurrentMinorVersion = 0;
 };
 
 struct ReadyToRunHeader

src/coreclr/runtime/amd64/WriteBarriers.S

@@ -249,96 +249,3 @@ LEAF_ENTRY RhpCheckedXchg, _TEXT
 
 LEAF_END RhpCheckedXchg, _TEXT
 
-//
-// RhpByRefAssignRef simulates movs instruction for object references.
-//
-// On entry:
-//      rdi: address of ref-field (assigned to)
-//      rsi: address of the data (source)
-//
-// On exit:
-//      rdi, rsi are incremented by 8,
-//      rcx, rax: trashed
-//
-// NOTE: Keep in sync with RBM_CALLEE_TRASH_WRITEBARRIER_BYREF and RBM_CALLEE_GCTRASH_WRITEBARRIER_BYREF
-//       if you add more trashed registers.
-//
-// WARNING: Code in EHHelpers.cpp makes assumptions about write barrier code, in particular:
-// - Function "InWriteBarrierHelper" assumes an AV due to passed in null pointer will happen at RhpByRefAssignRefAVLocation1/2
-// - Function "UnwindSimpleHelperToCaller" assumes the stack contains just the pushed return address
-LEAF_ENTRY RhpByRefAssignRef, _TEXT
-ALTERNATE_ENTRY RhpByRefAssignRefAVLocation1
-    mov     rcx, [rsi]
-#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 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.
-    cmp     rdi, [C_VAR(g_lowest_address)]
-    jb      LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-    cmp     rdi, [C_VAR(g_highest_address)]
-    jae     LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-
-    // Update the shadow copy of the heap with the same value just written to the same heap. (A no-op unless
-    // we're in a debug build and write barrier checking has been enabled).
-    UPDATE_GC_SHADOW BASENAME, rcx, rdi
-
-#ifdef FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP
-    cmp     qword ptr [C_VAR(g_write_watch_table)], 0x0
-    je      LOCAL_LABEL(RhpByRefAssignRef_CheckCardTable)
-
-    mov     rax, rdi
-    shr     rax, 0xC // SoftwareWriteWatch::AddressToTableByteIndexShift
-    add     rax, [C_VAR(g_write_watch_table)]
-    cmp     byte ptr [rax], 0x0
-    jne     LOCAL_LABEL(RhpByRefAssignRef_CheckCardTable)
-    mov     byte ptr [rax], 0xFF
-#endif
-
-LOCAL_LABEL(RhpByRefAssignRef_CheckCardTable):
-
-    // If the reference is to an object that's not in an ephemeral generation we have no need to track it
-    // (since the object won't be collected or moved by an ephemeral collection).
-    cmp     rcx, [C_VAR(g_ephemeral_low)]
-    jb      LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-    cmp     rcx, [C_VAR(g_ephemeral_high)]
-    jae     LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-
-    // move current rdi value into rcx, we need to keep rdi and eventually increment by 8
-    mov     rcx, rdi
-
-    // We have a location on the GC heap being updated with a reference to an ephemeral object so we must
-    // track this write. The location address is translated into an offset in the card table bitmap. We set
-    // an entire byte in the card table since it's quicker than messing around with bitmasks and we only write
-    // the byte if it hasn't already been done since writes are expensive and impact scaling.
-    shr     rcx, 0x0B
-    mov     rax, [C_VAR(g_card_table)]
-    cmp     byte ptr [rcx + rax], 0x0FF
-    je      LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-
-// We get here if it's necessary to update the card table.
-    mov     byte ptr [rcx + rax], 0xFF
-
-#ifdef FEATURE_MANUALLY_MANAGED_CARD_BUNDLES
-    // Shift rcx by 0x0A more to get the card bundle byte (we shifted by 0x0B already)
-    shr     rcx, 0x0A
-    add     rcx, [C_VAR(g_card_bundle_table)]
-    cmp     byte ptr [rcx], 0xFF
-    je      LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired)
-
-    mov     byte ptr [rcx], 0xFF
-#endif
-
-LOCAL_LABEL(RhpByRefAssignRef_NoBarrierRequired):
-    // Increment the pointers before leaving
-    add     rdi, 0x8
-    add     rsi, 0x8
-    ret
-LEAF_END RhpByRefAssignRef, _TEXT

src/coreclr/runtime/amd64/WriteBarriers.asm

@@ -257,90 +257,4 @@ LEAF_ENTRY RhpCheckedXchg, _TEXT
 
 LEAF_END RhpCheckedXchg, _TEXT
 
-;;
-;; RhpByRefAssignRef simulates movs instruction for object references.
-;;
-;; On entry:
-;;      rdi: address of ref-field (assigned to)
-;;      rsi: address of the data (source)
-;;
-;; On exit:
-;;      rdi, rsi are incremented by 8,
-;;      rcx, rax: trashed
-;;
-;; NOTE: Keep in sync with RBM_CALLEE_TRASH_WRITEBARRIER_BYREF and RBM_CALLEE_GCTRASH_WRITEBARRIER_BYREF
-;;       if you add more trashed registers.
-;;
-;; WARNING: Code in EHHelpers.cpp makes assumptions about write barrier code, in particular:
-;; - Function "InWriteBarrierHelper" assumes an AV due to passed in null pointer will happen at RhpByRefAssignRefAVLocation1/2
-;; - Function "UnwindSimpleHelperToCaller" assumes the stack contains just the pushed return address
-LEAF_ENTRY RhpByRefAssignRef, _TEXT
-ALTERNATE_ENTRY RhpByRefAssignRefAVLocation1
-    mov     rcx, [rsi]
-ALTERNATE_ENTRY RhpByRefAssignRefAVLocation2
-    mov     [rdi], rcx
-
-    ;; Check whether the writes were even into the heap. If not there's no card update required.
-    cmp     rdi, [g_lowest_address]
-    jb      RhpByRefAssignRef_NoBarrierRequired
-    cmp     rdi, [g_highest_address]
-    jae     RhpByRefAssignRef_NoBarrierRequired
-
-    ;; Update the shadow copy of the heap with the same value just written to the same heap. (A no-op unless
-    ;; we're in a debug build and write barrier checking has been enabled).
-    UPDATE_GC_SHADOW BASENAME, rcx, rdi
-
-ifdef FEATURE_USE_SOFTWARE_WRITE_WATCH_FOR_GC_HEAP
-    cmp     [g_write_watch_table], 0
-    je      RhpByRefAssignRef_CheckCardTable
-
-    mov     rax, rdi
-    shr     rax, 0Ch ;; SoftwareWriteWatch::AddressToTableByteIndexShift
-    add     rax, [g_write_watch_table]
-    cmp     byte ptr [rax], 0
-    jne     RhpByRefAssignRef_CheckCardTable
-    mov     byte ptr [rax], 0FFh
-endif
-
-RhpByRefAssignRef_CheckCardTable:
-
-    ;; If the reference is to an object that's not in an ephemeral generation we have no need to track it
-    ;; (since the object won't be collected or moved by an ephemeral collection).
-    cmp     rcx, [g_ephemeral_low]
-    jb      RhpByRefAssignRef_NoBarrierRequired
-    cmp     rcx, [g_ephemeral_high]
-    jae     RhpByRefAssignRef_NoBarrierRequired
-
-    ;; move current rdi value into rcx, we need to keep rdi and eventually increment by 8
-    mov     rcx, rdi
-
-    ;; We have a location on the GC heap being updated with a reference to an ephemeral object so we must
-    ;; track this write. The location address is translated into an offset in the card table bitmap. We set
-    ;; an entire byte in the card table since it's quicker than messing around with bitmasks and we only write
-    ;; the byte if it hasn't already been done since writes are expensive and impact scaling.
-    shr     rcx, 0Bh
-    mov     rax, [g_card_table]
-    cmp     byte ptr [rcx + rax], 0FFh
-    je      RhpByRefAssignRef_NoBarrierRequired
-
-;; We get here if it's necessary to update the card table.
-    mov     byte ptr [rcx + rax], 0FFh
-
-ifdef FEATURE_MANUALLY_MANAGED_CARD_BUNDLES
-    ;; Shift rcx by 0Ah more to get the card bundle byte (we shifted by 0Bh already)
-    shr     rcx, 0Ah
-    add     rcx, [g_card_bundle_table]
-    cmp     byte ptr [rcx], 0FFh
-    je      RhpByRefAssignRef_NoBarrierRequired
-
-    mov     byte ptr [rcx], 0FFh
-endif
-
-RhpByRefAssignRef_NoBarrierRequired:
-    ;; Increment the pointers before leaving
-    add     rdi, 8h
-    add     rsi, 8h
-    ret
-LEAF_END RhpByRefAssignRef, _TEXT
-
     end