dotnet · jkotas · Jan 17, 2025 · Jan 12, 2025 · Jan 12, 2025 · Jan 12, 2025
diff --git a/src/coreclr/jit/emitriscv64.cpp b/src/coreclr/jit/emitriscv64.cpp
@@ -1627,7 +1627,11 @@ unsigned emitter::emitOutputCall(const insGroup* ig, BYTE* dst, instrDesc* id, c
         int reg2 = ((int)addr & 1) + 10;
         addr     = addr ^ 1;
 
-        assert(isValidSimm32(addr - (ssize_t)dst));
+        if (!emitComp->opts.compReloc)
+        {
+            assert(isValidSimm32(addr - (ssize_t)dst));
+        }
+
         assert((addr & 1) == 0);
 
         dst += 4;

diff --git a/src/coreclr/jit/emitriscv64.h b/src/coreclr/jit/emitriscv64.h
@@ -194,11 +194,11 @@ static bool isValidSimm21(ssize_t value)
     return -(((int)1) << 20) <= value && value < (((int)1) << 20);
 };
 
-// Returns true if 'value' is a legal signed immediate 32 bit encoding.
+// Returns true if 'value' is a legal signed immediate 32-bit encoding with the offset adjustment.
 static bool isValidSimm32(ssize_t value)
 {
-    return -(((ssize_t)1) << 31) <= value && value < (((ssize_t)1) << 31);
-};
+    return (-(((ssize_t)1) << 31) - 0x800) <= value && value < (((ssize_t)1) << 31) - 0x800;
+}
 
 // Returns the number of bits used by the given 'size'.
 inline static unsigned getBitWidth(emitAttr size)

@@ -179,7 +179,6 @@ The .NET Foundation licenses this file to you under the MIT license.
       <NativeLibrary Include="$(IlcFrameworkNativePath)libbrotlicommon.a" />
     </ItemGroup>
 
-
     <ItemGroup Condition="'$(StaticICULinking)' == 'true' and '$(NativeLib)' != 'Static' and '$(InvariantGlobalization)' != 'true'">
       <NativeLibrary Include="$(IntermediateOutputPath)libs/System.Globalization.Native/build/libSystem.Globalization.Native.a" />
       <DirectPInvoke Include="libSystem.Globalization.Native" />
@@ -222,6 +221,8 @@ The .NET Foundation licenses this file to you under the MIT license.
       <NativeSystemLibrary Include="log" Condition="'$(_linuxLibcFlavor)' == 'bionic'" />
       <NativeSystemLibrary Include="icucore" Condition="'$(_IsApplePlatform)' == 'true'" />
       <NativeSystemLibrary Include="m" />
+      <!-- See the comment in PalInterlockedCompareExchange128 for details. -->
+      <NativeSystemLibrary Include="atomic" Condition="'$(_targetArchitecture)' == 'riscv64'" />
     </ItemGroup>
 
     <ItemGroup>

@@ -128,10 +128,6 @@ endif ; TRASH_SAVED_ARGUMENT_REGISTERS
 
 ALTERNATE_ENTRY ReturnFrom&FunctionName
 
-        ; We cannot make the label public as that tricks DIA stackwalker into thinking
-        ; it's the beginning of a method. For this reason we export the address
-        ; by means of an auxiliary variable.
-
         ; restore fp argument registers
         movdqa          xmm0, [rsp + DISTANCE_FROM_CHILDSP_TO_FP_REGS      ]
         movdqa          xmm1, [rsp + DISTANCE_FROM_CHILDSP_TO_FP_REGS + 10h]

@@ -125,10 +125,6 @@ NESTED_ENTRY Rhp\FunctionName, _TEXT, NoHandler
 
 GLOBAL_LABEL ReturnFrom\FunctionName
 
-        // We cannot make the label public as that tricks DIA stackwalker into thinking
-        // it's the beginning of a method. For this reason we export an auxiliary variable
-        // holding the address instead.
-
         // Move the result (the target address) to r12 so it doesn't get overridden when we restore the
         // argument registers. Additionally make sure the thumb2 bit is set.
         orr	         r12, r0, #1

@@ -129,9 +129,6 @@
         mov         x1, xip1                                        // Second parameter to target function
         blr         xip0
 
-        // We cannot make the label public as that tricks DIA stackwalker into thinking
-        // it's the beginning of a method. For this reason we export an auxiliary variable
-        // holding the address instead.
 ALTERNATE_ENTRY ReturnFrom\FunctionName
 
         // Move the result (the target address) to x12 so it doesn't get overridden when we restore the

@@ -120,9 +120,6 @@
         mov         x1, xip1                                        ;; Second parameter to target function
         blr         xip0
 
-        ;; We cannot make the label public as that tricks DIA stackwalker into thinking
-        ;; it's the beginning of a method. For this reason we export an auxiliary variable
-        ;; holding the address instead.
     ALTERNATE_ENTRY ReturnFrom$FunctionName
 
         ;; Move the result (the target address) to x12 so it doesn't get overridden when we restore the

@@ -76,10 +76,6 @@ ALTERNATE_ENTRY _Rhp&FunctionName&@0
 
 ALTERNATE_ENTRY _ReturnFrom&FunctionName
 
-        ; We cannot make the label public as that tricks DIA stackwalker into thinking
-        ; it's the beginning of a method. For this reason we export an auxiliary variable
-        ; holding the address instead.
-
         pop edx
         pop ecx
         add esp, 8

@@ -137,9 +137,6 @@
         ori  $a1, $t8, 0                                         // Second parameter to target function
         jirl  $ra, $t7, 0
 
-        // We cannot make the label public as that tricks DIA stackwalker into thinking
-        // it's the beginning of a method. For this reason we export an auxiliary variable
-        // holding the address instead.
     ALTERNATE_ENTRY ReturnFrom\FunctionName
 
         // Move the result (the target address) to t3 so it doesn't get overridden when we restore the

@@ -328,7 +328,7 @@
 
         // Normal case where a valid return address location is hijacked
         sd    a1, 0(a3)
-        tail  ClearThreadState
+        tail  LOCAL_LABEL(ClearThreadState)
 
 LOCAL_LABEL(TailCallWasHijacked):
 

@@ -136,6 +136,8 @@
         mv a1, t1                                         // Second parameter to target function
         jalr t0, t1, 0                                    // Jump to the function in t1
 
+    ALTERNATE_ENTRY ReturnFrom\FunctionName
+
         // Restore the result address from t2
         mv t2, a0                                       // Move result to t2
 
@@ -169,7 +171,6 @@
 
     .endm
 
-
     // To enable proper step-in behavior in the debugger, we need to have two instances
     // of the thunk. For the first one, the debugger steps into the call in the function,
     // for the other, it steps over it.

@@ -94,21 +94,28 @@ FORCEINLINE int64_t PalInterlockedCompareExchange64(_Inout_ int64_t volatile *pD
     return result;
 }
 
-#if defined(HOST_AMD64) || defined(HOST_ARM64) || defined(HOST_LOONGARCH64) || defined(HOST_RISCV64)
+#if defined(HOST_64BIT)
 FORCEINLINE uint8_t PalInterlockedCompareExchange128(_Inout_ int64_t volatile *pDst, int64_t iValueHigh, int64_t iValueLow, int64_t *pComparandAndResult)
 {
     __int128_t iComparand = ((__int128_t)pComparandAndResult[1] << 64) + (uint64_t)pComparandAndResult[0];
-    // TODO-LOONGARCH64: for LoongArch64, it supports 128bits atomic from 3A6000-CPU which is ISA1.1's version.
-    // The LA64's compiler will translate the `__sync_val_compare_and_swap` into calling the libatomic's library interface to emulate
-    // the 128-bit CAS by mutex_lock if the target processor doesn't support the ISA1.1.
-    // But this emulation by libatomic doesn't satisfy requirements here which it must update two adjacent pointers atomically.
-    // this is being discussed in https://github.com/dotnet/runtime/issues/109276.
+
+    // TODO-LOONGARCH64: the 128-bit CAS is supported starting from the 3A6000 CPU (ISA1.1).
+    // When running on older hardware that doesn't support native CAS-128, the system falls back
+    // to a mutex-based approach via libatomic, which is not suitable for runtime requirements.
+    //
+    // TODO-RISCV64: double-check if libatomic's emulated CAS-128 works as expected once AOT applications are
+    // functional on linux-riscv64: https://github.com/dotnet/runtime/issues/106223.
+    // CAS-128 is natively supported starting with the Zacas extension in Linux 6.8; however, hardware support
+    // for RVA23 profile is not available at the time of writing.
+    //
+    // See https://github.com/dotnet/runtime/issues/109276.
+
     __int128_t iResult = __sync_val_compare_and_swap((__int128_t volatile*)pDst, iComparand, ((__int128_t)iValueHigh << 64) + (uint64_t)iValueLow);
     PalInterlockedOperationBarrier();
     pComparandAndResult[0] = (int64_t)iResult; pComparandAndResult[1] = (int64_t)(iResult >> 64);
     return iComparand == iResult;
 }
-#endif // HOST_AMD64 || HOST_ARM64 || HOST_LOONGARCH64 || HOST_RISCV64
+#endif // HOST_64BIT
 
 #ifdef HOST_64BIT
 

@@ -44,18 +44,12 @@ C_FUNC(\Name):
 .endm
 
 .macro PREPARE_EXTERNAL_VAR Name, HelperReg
-        lui \HelperReg, %hi(C_FUNC(\Name))
-        addi \HelperReg, \HelperReg, %lo(C_FUNC(\Name))
-.endm
-
-.macro PREPARE_EXTERNAL_VAR_INDIRECT Name, HelperReg
-        lui \HelperReg, %hi(C_FUNC(\Name))
-        ld  \HelperReg, %lo(C_FUNC(\Name))(\HelperReg)
+    la \HelperReg, C_FUNC(\Name) // Resolves the address in one step
 .endm
 
 .macro PREPARE_EXTERNAL_VAR_INDIRECT_W Name, HelperReg
-        lui \HelperReg, %hi(C_FUNC(\Name))
-        lw  \HelperReg, %lo(C_FUNC(\Name))(\HelperReg)
+    la \HelperReg, C_FUNC(\Name)
+    lw \HelperReg, 0(\HelperReg)
 .endm
 
 .macro PROLOG_STACK_ALLOC Size

@@ -301,7 +301,6 @@ public void EmitReloc(ISymbolNode symbol, RelocType relocType, int delta = 0)
                 case RelocType.IMAGE_REL_BASED_LOONGARCH64_JIR:
 
                 case RelocType.IMAGE_REL_BASED_RISCV64_PC:
-                case RelocType.IMAGE_REL_BASED_RISCV64_JALR:
                     Debug.Assert(delta == 0);
                     // Do not vacate space for this kind of relocation, because
                     // the space is embedded in the instruction.

@@ -20,7 +20,6 @@ public enum RelocType
         IMAGE_REL_BASED_LOONGARCH64_PC       = 0x16,   // LoongArch64: pcalau12i+imm12
         IMAGE_REL_BASED_LOONGARCH64_JIR      = 0x17,   // LoongArch64: pcaddu18i+jirl
         IMAGE_REL_BASED_RISCV64_PC           = 0x18,   // RiscV64: auipc
-        IMAGE_REL_BASED_RISCV64_JALR         = 0x19,   // RiscV64: jalr (indirect jump)
         IMAGE_REL_BASED_RELPTR32             = 0x7C,   // 32-bit relative address from byte starting reloc
                                                        // This is a special NGEN-specific relocation type
                                                        // for relative pointer (used to make NGen relocation
@@ -470,7 +469,7 @@ private static unsafe int GetRiscV64PC(uint* pCode)
         private static unsafe void PutRiscV64PC(uint* pCode, long imm32)
         {
             // Verify that we got a valid offset
-            Debug.Assert((int)imm32 == imm32);
+            Debug.Assert((imm32 >= (long)-0x80000000 - 0x800) && (imm32 < (long)0x80000000 - 0x800));
 
             int doff = (int)(imm32 & 0xfff);
             uint auipcInstr = *pCode;

@@ -111,7 +111,7 @@ public void EmitJMP(ISymbolNode symbol)
             }
             else
             {
-                Builder.EmitReloc(symbol, RelocType.IMAGE_REL_BASED_RISCV64_JALR);
+                Builder.EmitReloc(symbol, RelocType.IMAGE_REL_BASED_RISCV64_PC);
                 EmitPC(Register.X29); // auipc x29, 0
                 EmitJALR(Register.X0, Register.X29, 0); // jalr x0, 0(x29)
             }

@@ -552,9 +552,8 @@ private void EmitRelocationsRiscV64(int sectionIndex, List<SymbolicRelocation> r
                     {
                         IMAGE_REL_BASED_DIR64 => R_RISCV_64,
                         IMAGE_REL_BASED_HIGHLOW => R_RISCV_32,
-                        IMAGE_REL_BASED_RELPTR32 => R_RISCV_RELATIVE,
-                        IMAGE_REL_BASED_RISCV64_PC => R_RISCV_PCREL_HI20,
-                        IMAGE_REL_BASED_RISCV64_JALR => R_RISCV_CALL32,
+                        IMAGE_REL_BASED_RELPTR32 => R_RISCV_64_LO12,
+                        IMAGE_REL_BASED_RISCV64_PC => R_RISCV_64_HI20,
                         _ => throw new NotSupportedException("Unknown relocation type: " + symbolicRelocation.Type)
                     };