Remove -Wno-unused-function -Wno-tautological-compare -Wno-unused-value for clrjit projects (#128271)

We currently define the followings for the entire native code:

- [ ] add_compile_options(-Wno-unused-variable)
- [x] add_compile_options(-Wno-unused-value)
- [x] add_compile_options(-Wno-unused-function)
- [x] add_compile_options(-Wno-tautological-compare)
- [ ] add_compile_options(-Wno-unknown-pragmas)


my initial attempt to remove them all led to a very big diff so I
decided to focus on JIT first.

---------

Co-authored-by: EgorBo <egorbo@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: 3 people

src/coreclr/jit/CMakeLists.txt

@@ -16,6 +16,15 @@ if (MSVC)
   add_compile_options($<$<COMPILE_LANGUAGE:C,CXX>:/permissive->)
 endif()
 
+# The JIT enforces -Wunused-function, -Wtautological-compare and -Wunused-value
+# (overriding the repo-wide -Wno-* counterparts from configurecompiler.cmake) so
+# that dead helpers, always-true/always-false comparisons and discarded
+# expressions are caught early. Any helper or comparison that is only meaningful
+# under a target/DEBUG #ifdef must be guarded by the same condition.
+if (CLR_CMAKE_HOST_UNIX OR CLR_CMAKE_HOST_WASI)
+  add_compile_options(-Wunused-function -Wtautological-compare -Wunused-value)
+endif()
+
 function(create_standalone_jit)
 
   set(oneValueArgs TARGET OS ARCH)

src/coreclr/jit/emitriscv64.cpp

@@ -2882,18 +2882,6 @@ static unsigned UpperNBitsOfWordSignExtend(ssize_t word)
     return UpperNBitsOfWord<MaskSize>(word + kSignExtend);
 }
 
-static unsigned UpperWordOfDoubleWord(ssize_t immediate)
-{
-    return static_cast<unsigned>(immediate >> 32);
-}
-
-static unsigned LowerWordOfDoubleWord(ssize_t immediate)
-{
-    static constexpr size_t kWordMask = WordMask(32);
-
-    return static_cast<unsigned>(immediate & kWordMask);
-}
-
 template <uint8_t UpperMaskSize, uint8_t LowerMaskSize>
 static ssize_t DoubleWordSignExtend(ssize_t doubleWord)
 {
@@ -2903,20 +2891,6 @@ static ssize_t DoubleWordSignExtend(ssize_t doubleWord)
     return doubleWord + (kLowerSignExtend | kUpperSignExtend);
 }
 
-template <uint8_t UpperMaskSize>
-static ssize_t UpperWordOfDoubleWordSingleSignExtend(ssize_t doubleWord)
-{
-    static constexpr size_t kUpperSignExtend = static_cast<size_t>(1) << (31 - UpperMaskSize);
-
-    return UpperWordOfDoubleWord(doubleWord + kUpperSignExtend);
-}
-
-template <uint8_t UpperMaskSize, uint8_t LowerMaskSize>
-static ssize_t UpperWordOfDoubleWordDoubleSignExtend(ssize_t doubleWord)
-{
-    return UpperWordOfDoubleWord(DoubleWordSignExtend<UpperMaskSize, LowerMaskSize>(doubleWord));
-}
-
 /*static*/ unsigned emitter::TrimSignedToImm12(ssize_t imm12)
 {
     assert(isValidSimm12(imm12));
@@ -5690,7 +5664,7 @@ emitter::insExecutionCharacteristics emitter::getInsExecutionCharacteristics(ins
             }
 
             regNumber baseReg = id->idReg2();
-            if (baseReg != REG_SP || baseReg != REG_FP)
+            if ((baseReg != REG_SP) && (baseReg != REG_FP))
                 result.insLatency += PERFSCORE_LATENCY_1C; // assume non-stack load/stores are more likely to cache-miss
 
             result.insThroughput += immediateBuildingCost;

src/coreclr/jit/emitxarch.cpp

@@ -1665,6 +1665,7 @@ bool emitter::Is4ByteSSEInstruction(instruction ins) const
     return !UseVEXEncoding() && EncodedBySSE38orSSE3A(ins);
 }
 
+#ifdef DEBUG
 //------------------------------------------------------------------------
 // isLowSIMDReg: Checks if a register is a register supported by any SIMD encoding
 //
@@ -1681,6 +1682,7 @@ static bool isLowSimdReg(regNumber reg)
     return (reg >= REG_XMM0) && (reg <= REG_XMM7);
 #endif
 }
+#endif // DEBUG
 
 //------------------------------------------------------------------------
 // GetEmbRoundingMode: Get the rounding mode for embedded rounding

src/coreclr/jit/gentree.cpp

@@ -10467,7 +10467,11 @@ bool GenTreeOp::UsesDivideByConstOptimized(Compiler* comp)
         if (isSignedDivide)
         {
             // If the divisor is the minimum representable integer value then the result is either 0 or 1
-            if ((divType == TYP_INT && divisorValue == INT_MIN) || (divType == TYP_LONG && divisorValue == INT64_MIN))
+            if ((divType == TYP_INT && divisorValue == INT_MIN)
+#if defined(TARGET_64BIT)
+                || (divType == TYP_LONG && divisorValue == INT64_MIN)
+#endif
+            )
             {
                 return true;
             }
@@ -32026,7 +32030,7 @@ NamedIntrinsic GenTreeHWIntrinsic::GetHWIntrinsicIdForCmpOp(Compiler*  comp,
             }
             else if (isScalar)
             {
-                reverseCond ? NI_X86Base_CompareScalarNotLessThanOrEqual : NI_X86Base_CompareScalarGreaterThan;
+                id = reverseCond ? NI_X86Base_CompareScalarNotLessThanOrEqual : NI_X86Base_CompareScalarGreaterThan;
             }
             else
             {

src/coreclr/jit/hwintrinsic.cpp

@@ -1661,46 +1661,6 @@ static bool impIsTableDrivenHWIntrinsic(NamedIntrinsic intrinsicId, HWIntrinsicC
     return (category != HW_Category_Special) && !HWIntrinsicInfo::HasSpecialImport(intrinsicId);
 }
 
-//------------------------------------------------------------------------
-// isSupportedBaseType
-//
-// Arguments:
-//    intrinsicId - HW intrinsic id
-//    baseJitType - Base JIT type of the intrinsic.
-//
-// Return Value:
-//    returns true if the baseType is supported for given intrinsic.
-//
-static bool isSupportedBaseType(NamedIntrinsic intrinsic, CorInfoType baseJitType)
-{
-    if (baseJitType == CORINFO_TYPE_UNDEF)
-    {
-        return false;
-    }
-
-    var_types baseType = JitType2PreciseVarType(baseJitType);
-
-    // We don't actually check the intrinsic outside of the false case as we expect
-    // the exposed managed signatures are either generic and support all types
-    // or they are explicit and support the type indicated.
-
-    if (varTypeIsArithmetic(baseType))
-    {
-        return true;
-    }
-
-#ifdef DEBUG
-    CORINFO_InstructionSet isa = HWIntrinsicInfo::lookupIsa(intrinsic);
-#ifdef TARGET_XARCH
-    assert((isa == InstructionSet_Vector512) || (isa == InstructionSet_Vector256) || (isa == InstructionSet_Vector128));
-#endif // TARGET_XARCH
-#ifdef TARGET_ARM64
-    assert((isa == InstructionSet_Vector64) || (isa == InstructionSet_Vector128));
-#endif // TARGET_ARM64
-#endif // DEBUG
-    return false;
-}
-
 static bool isSupportedBaseType(NamedIntrinsic intrinsic, var_types baseType)
 {
     if (baseType == TYP_UNDEF)

src/coreclr/jit/ifconversion.cpp

@@ -742,6 +742,7 @@ GenTree* OptIfConversionDsc::TryOptimizeSelect(GenTreeConditional* select)
     return nullptr;
 }
 
+#ifdef TARGET_RISCV64
 struct IntConstSelectOper
 {
     genTreeOps oper;
@@ -794,6 +795,7 @@ static IntConstSelectOper MatchIntConstSelectValues(int64_t trueVal, int64_t fal
 
     return {GT_NONE};
 }
+#endif // TARGET_RISCV64
 
 //-----------------------------------------------------------------------------
 // TrySelectToCnsOpCond: Try to optimize:

src/coreclr/jit/importercalls.cpp

@@ -4776,8 +4776,7 @@ GenTree* Compiler::impIntrinsic(CORINFO_CLASS_HANDLE    clsHnd,
                                 // This is now known to be a multi-dimension array with a constant dimension
                                 // that is in range; we can expand it as an intrinsic.
 
-                                impPopStack().val; // Pop the dim and array object; we already have a pointer to them.
-                                impPopStack().val;
+                                impPopStack(2); // Pop the dim and array object; we already have a pointer to them.
 
                                 // Make sure there are no global effects in the array (such as it being a function
                                 // call), so we can mark the generated indirection with GTF_IND_INVARIANT. In the

src/coreclr/jit/lower.cpp

@@ -8157,8 +8157,11 @@ bool Lowering::TryLowerConstIntUDivOrUMod(GenTreeOp* divMod)
     {
         // If the divisor is greater or equal than 2^(N - 1) then the result is 1
         // iff the dividend is greater or equal than the divisor.
-        if (((type == TYP_INT) && (divisorValue > (UINT32_MAX / 2))) ||
-            ((type == TYP_LONG) && (divisorValue > (UINT64_MAX / 2))))
+        if (((type == TYP_INT) && (divisorValue > (UINT32_MAX / 2)))
+#if defined(TARGET_64BIT)
+            || ((type == TYP_LONG) && (divisorValue > (UINT64_MAX / 2)))
+#endif
+        )
         {
             divMod->ChangeOper(GT_GE);
             divMod->SetUnsigned();
@@ -8448,7 +8451,11 @@ bool Lowering::TryLowerConstIntDivOrMod(GenTree* node, GenTree** nextNode)
 
     if (isDiv)
     {
-        if ((type == TYP_INT && divisorValue == INT_MIN) || (type == TYP_LONG && divisorValue == INT64_MIN))
+        if ((type == TYP_INT && divisorValue == INT_MIN)
+#if defined(TARGET_64BIT)
+            || (type == TYP_LONG && divisorValue == INT64_MIN)
+#endif
+        )
         {
             // If the divisor is the minimum representable integer value then we can use a compare,
             // the result is 1 iff the dividend equals divisor.
@@ -10400,6 +10407,7 @@ static bool IsStoreCoalescingInvariantNode(Compiler* compiler, GenTree* node, bo
     return node->OperIs(GT_LCL_VAR) && !compiler->lvaVarAddrExposed(node->AsLclVar()->GetLclNum());
 }
 
+#if defined(TARGET_XARCH) || defined(TARGET_ARM64)
 //------------------------------------------------------------------------
 // TryGetStoreCoalescingConstantBits: get the raw bits for a constant used by store
 //    coalescing.
@@ -10442,6 +10450,7 @@ static bool TryGetStoreCoalescingConstantBits(GenTree* value, uint64_t* bits)
 
     return false;
 }
+#endif // TARGET_XARCH || TARGET_ARM64
 
 //------------------------------------------------------------------------
 // GetLoadStoreCoalescingData: given a STOREIND/IND node, get the data needed to perform

src/coreclr/jit/scev.cpp

@@ -1469,6 +1469,7 @@ ValueNumPair ScalarEvolutionContext::MaterializeVN(Scev* scev)
     return Materialize(scev, false, nullptr, &vnp) ? vnp : ValueNumPair();
 }
 
+#ifdef DEBUG
 //------------------------------------------------------------------------
 // RelopEvaluationResultString: Convert a RelopEvaluationResult to a string.
 //
@@ -1492,6 +1493,7 @@ static const char* RelopEvaluationResultString(RelopEvaluationResult result)
             return "n/a";
     }
 }
+#endif // DEBUG
 
 //------------------------------------------------------------------------
 // EvaluateRelop: