[NativeAOT/ARM] Prevent misoptimization by clang (#97811)

* Fix *AVLocation to be global labels without the Thumb bit to prevent misoptimization

* Remove Thumb bit from assembly location constants and its masking

* Introduce CODE_LOCATION type and use it instead of "void*".

src/coreclr/nativeaot/Runtime/CommonMacros.h

@@ -170,6 +170,9 @@ inline bool IS_ALIGNED(T* val, uintptr_t alignment);
 #define THUMB_CODE 1
 #endif
 
+// Type for external code location references inside the assembly code.
+typedef uint8_t CODE_LOCATION;
+
 //
 // Define an unmanaged function called from managed code that needs to execute in co-operative GC mode. (There
 // should be very few of these, most such functions will be simply p/invoked).

src/coreclr/nativeaot/Runtime/EHHelpers.cpp

@@ -281,25 +281,25 @@ EXTERN_C void* RhpThrowHwEx2 = NULL;
 EXTERN_C void* RhpRethrow2   = NULL;
 #endif
 
-EXTERN_C void * RhpAssignRefAVLocation;
-EXTERN_C void * RhpCheckedAssignRefAVLocation;
-EXTERN_C void * RhpCheckedLockCmpXchgAVLocation;
-EXTERN_C void * RhpCheckedXchgAVLocation;
+EXTERN_C CODE_LOCATION RhpAssignRefAVLocation;
+EXTERN_C CODE_LOCATION RhpCheckedAssignRefAVLocation;
+EXTERN_C CODE_LOCATION RhpCheckedLockCmpXchgAVLocation;
+EXTERN_C CODE_LOCATION RhpCheckedXchgAVLocation;
 #if !defined(HOST_AMD64) && !defined(HOST_ARM64)
-EXTERN_C void * RhpLockCmpXchg8AVLocation;
-EXTERN_C void * RhpLockCmpXchg16AVLocation;
-EXTERN_C void * RhpLockCmpXchg32AVLocation;
-EXTERN_C void * RhpLockCmpXchg64AVLocation;
+EXTERN_C CODE_LOCATION RhpLockCmpXchg8AVLocation;
+EXTERN_C CODE_LOCATION RhpLockCmpXchg16AVLocation;
+EXTERN_C CODE_LOCATION RhpLockCmpXchg32AVLocation;
+EXTERN_C CODE_LOCATION RhpLockCmpXchg64AVLocation;
 #endif
-EXTERN_C void * RhpByRefAssignRefAVLocation1;
+EXTERN_C CODE_LOCATION RhpByRefAssignRefAVLocation1;
 
 #if !defined(HOST_ARM64)
-EXTERN_C void * RhpByRefAssignRefAVLocation2;
+EXTERN_C CODE_LOCATION RhpByRefAssignRefAVLocation2;
 #endif
 
 #if defined(HOST_ARM64) && !defined(LSE_INSTRUCTIONS_ENABLED_BY_DEFAULT)
-EXTERN_C void* RhpCheckedLockCmpXchgAVLocation2;
-EXTERN_C void* RhpCheckedXchgAVLocation2;
+EXTERN_C CODE_LOCATION RhpCheckedLockCmpXchgAVLocation2;
+EXTERN_C CODE_LOCATION RhpCheckedXchgAVLocation2;
 #endif
 
 static bool InWriteBarrierHelper(uintptr_t faultingIP)
@@ -336,22 +336,22 @@ static bool InWriteBarrierHelper(uintptr_t faultingIP)
         ASSERT(*(uint8_t*)writeBarrierAVLocations[i] != 0xE9); // jmp XXXXXXXX
 #endif
 
-        if (PCODEToPINSTR(writeBarrierAVLocations[i]) == faultingIP)
+        if (writeBarrierAVLocations[i] == faultingIP)
             return true;
     }
 #endif // USE_PORTABLE_HELPERS
 
     return false;
 }
 
-EXTERN_C void* RhpInitialInterfaceDispatch;
-EXTERN_C void* RhpInterfaceDispatchAVLocation1;
-EXTERN_C void* RhpInterfaceDispatchAVLocation2;
-EXTERN_C void* RhpInterfaceDispatchAVLocation4;
-EXTERN_C void* RhpInterfaceDispatchAVLocation8;
-EXTERN_C void* RhpInterfaceDispatchAVLocation16;
-EXTERN_C void* RhpInterfaceDispatchAVLocation32;
-EXTERN_C void* RhpInterfaceDispatchAVLocation64;
+EXTERN_C CODE_LOCATION RhpInitialInterfaceDispatch;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation1;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation2;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation4;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation8;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation16;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation32;
+EXTERN_C CODE_LOCATION RhpInterfaceDispatchAVLocation64;
 
 static bool InInterfaceDispatchHelper(uintptr_t faultingIP)
 {
@@ -377,7 +377,7 @@ static bool InInterfaceDispatchHelper(uintptr_t faultingIP)
         ASSERT(*(uint8_t*)interfaceDispatchAVLocations[i] != 0xE9); // jmp XXXXXXXX
 #endif
 
-        if (PCODEToPINSTR(interfaceDispatchAVLocations[i]) == faultingIP)
+        if (interfaceDispatchAVLocations[i] == faultingIP)
             return true;
     }
 #endif // USE_PORTABLE_HELPERS

src/coreclr/nativeaot/Runtime/StackFrameIterator.cpp

@@ -76,7 +76,7 @@ GVAL_IMPL_INIT(PTR_VOID, g_RhpRethrow2Addr, PointerToRhpRethrow2);
 #ifdef DACCESS_COMPILE
 #define EQUALS_RETURN_ADDRESS(x, func_name) ((x) == g_ ## func_name ## Addr)
 #else
-#define EQUALS_RETURN_ADDRESS(x, func_name) (((x)) == (PTR_VOID)PCODEToPINSTR((PCODE)PointerTo ## func_name))
+#define EQUALS_RETURN_ADDRESS(x, func_name) (((x)) == (PointerTo ## func_name))
 #endif
 
 #ifdef DACCESS_COMPILE

src/coreclr/nativeaot/Runtime/arm/Interlocked.S

@@ -15,7 +15,7 @@
 // r2 = comparand
 LEAF_ENTRY RhpLockCmpXchg8, _TEXT
           dmb
-ALTERNATE_ENTRY RhpLockCmpXchg8AVLocation
+GLOBAL_LABEL RhpLockCmpXchg8AVLocation
 LOCAL_LABEL(CmpXchg8Retry):
           ldrexb       r3, [r0]
           cmp          r2, r3
@@ -38,7 +38,7 @@ LEAF_END RhpLockCmpXchg8, _TEXT
 LEAF_ENTRY RhpLockCmpXchg16, _TEXT
           uxth         r2, r2
           dmb
-ALTERNATE_ENTRY RhpLockCmpXchg16AVLocation
+GLOBAL_LABEL RhpLockCmpXchg16AVLocation
 LOCAL_LABEL(CmpXchg16Retry):
           ldrexh       r3, [r0]
           cmp          r2, r3
@@ -60,7 +60,7 @@ LEAF_END RhpLockCmpXchg16, _TEXT
 // r2 = comparand
 LEAF_ENTRY RhpLockCmpXchg32, _TEXT
           dmb
-ALTERNATE_ENTRY RhpLockCmpXchg32AVLocation
+GLOBAL_LABEL RhpLockCmpXchg32AVLocation
 LOCAL_LABEL(CmpXchg32Retry):
           ldrex        r3, [r0]
           cmp          r2, r3
@@ -81,7 +81,7 @@ LEAF_END RhpLockCmpXchg32, _TEXT
 // {r2,r3} = value
 // sp[0+8] = comparand
 LEAF_ENTRY RhpLockCmpXchg64, _TEXT
-ALTERNATE_ENTRY RhpLockCmpXchg64AVLocation
+GLOBAL_LABEL RhpLockCmpXchg64AVLocation
           ldr          r12, [r0]        // dummy read for null check
           PROLOG_PUSH  "{r4-r6,lr}"
           dmb

src/coreclr/nativeaot/Runtime/arm/StubDispatch.S

@@ -22,7 +22,7 @@ NESTED_ENTRY RhpInterfaceDispatch\entries, _TEXT, NoHandler
         ldr         r2, [r12, #OFFSETOF__InterfaceDispatchCell__m_pCache]
 
         // Load the MethodTable from the object instance in r0.
-        ALTERNATE_ENTRY RhpInterfaceDispatchAVLocation\entries
+        GLOBAL_LABEL RhpInterfaceDispatchAVLocation\entries
         ldr         r1, [r0]
 
         CurrentOffset = OFFSETOF__InterfaceDispatchCache__m_rgEntries

src/coreclr/nativeaot/Runtime/arm/WriteBarriers.S

@@ -164,9 +164,9 @@ ALTERNATE_ENTRY RhpAssignRef
 
           // Write the reference into the location. Note that we rely on the fact that no GC can occur between here
           // and the card table update we may perform below.
-ALTERNATE_ENTRY "RhpAssignRefAvLocation"\EXPORT_REG_NAME  // WriteBarrierFunctionAvLocation
+GLOBAL_LABEL "RhpAssignRefAvLocation"\EXPORT_REG_NAME  // WriteBarrierFunctionAvLocation
 .ifc \REFREG, r1
-ALTERNATE_ENTRY RhpAssignRefAVLocation
+GLOBAL_LABEL RhpAssignRefAVLocation
 .endif
           str          \REFREG, [r0]
 
@@ -234,9 +234,9 @@ ALTERNATE_ENTRY RhpCheckedAssignRef
           dmb
           // Write the reference into the location. Note that we rely on the fact that no GC can occur between here
           // and the card table update we may perform below.
-ALTERNATE_ENTRY "RhpCheckedAssignRefAvLocation"\EXPORT_REG_NAME // WriteBarrierFunctionAvLocation
+GLOBAL_LABEL "RhpCheckedAssignRefAvLocation"\EXPORT_REG_NAME // WriteBarrierFunctionAvLocation
 .ifc \REFREG, r1
-ALTERNATE_ENTRY RhpCheckedAssignRefAVLocation
+GLOBAL_LABEL RhpCheckedAssignRefAVLocation
 .endif
           str          \REFREG, [r0]
 
@@ -261,7 +261,7 @@ LEAF_ENTRY RhpCheckedLockCmpXchg, _TEXT
           // barrier must occur before the object reference update, so we have to do it unconditionally even
           // though the update may fail below.
           dmb
-ALTERNATE_ENTRY RhpCheckedLockCmpXchgAVLocation
+GLOBAL_LABEL RhpCheckedLockCmpXchgAVLocation
 LOCAL_LABEL(RhpCheckedLockCmpXchgRetry):
           ldrex        r3, [r0]
           cmp          r2, r3
@@ -286,7 +286,7 @@ LEAF_ENTRY RhpCheckedXchg, _TEXT
           // To implement our chosen memory model for ARM we insert a memory barrier at GC write barriers. This
           // barrier must occur before the object reference update.
           dmb
-ALTERNATE_ENTRY RhpCheckedXchgAVLocation
+GLOBAL_LABEL RhpCheckedXchgAVLocation
 LOCAL_LABEL(RhpCheckedXchgRetry):
           ldrex        r2, [r0]
           strex        r3, r1, [r0]
@@ -320,9 +320,9 @@ LEAF_ENTRY RhpByRefAssignRef, _TEXT
           // See comment in RhpAssignRef
           dmb
 
-ALTERNATE_ENTRY RhpByRefAssignRefAVLocation1
+GLOBAL_LABEL RhpByRefAssignRefAVLocation1
           ldr          r2, [r1]
-ALTERNATE_ENTRY RhpByRefAssignRefAVLocation2
+GLOBAL_LABEL RhpByRefAssignRefAVLocation2
           str          r2, [r0]
 
           // Check whether the writes were even into the heap. If not there's no card update required.

src/coreclr/nativeaot/Runtime/unix/unixasmmacrosarm.inc

@@ -56,6 +56,11 @@ C_FUNC(\Name):
 C_FUNC(\Name):
 .endm
 
+.macro GLOBAL_LABEL Name
+        .global C_FUNC(\Name)
+C_FUNC(\Name):
+.endm
+
 .macro LEAF_ENTRY Name, Section
         .thumb_func
         .global C_FUNC(\Name)
@@ -213,7 +218,7 @@ C_FUNC(\Name):
         .data
         .align      4
 C_FUNC(\Name):
-        .word       1b + 1            // Add 1 to indicate thumb code
+        .word       1b
         .global     C_FUNC(\Name)
         .text