[Arm64] Replace pairs of str with stp

src/coreclr/jit/emit.h

@@ -782,17 +782,18 @@ class emitter
         unsigned _idNoGC : 1;       // Some helpers don't get recorded in GC tables
 
 #ifdef TARGET_ARM64
-        opSize   _idOpSize : 3; // operand size: 0=1 , 1=2 , 2=4 , 3=8, 4=16
-        insOpts  _idInsOpt : 6; // options for instructions
-        unsigned _idLclVar : 1; // access a local on stack
+        opSize   _idOpSize : 3;    // operand size: 0=1 , 1=2 , 2=4 , 3=8, 4=16
+        insOpts  _idInsOpt : 6;    // options for instructions
+        unsigned _idLclVar : 1;    // access a local on stack
+        unsigned _idLclVarPair : 1 // carries information for 2 GC lcl vars.
 #endif
 
 #ifdef TARGET_LOONGARCH64
-        // TODO-LoongArch64: maybe delete on future.
-        opSize  _idOpSize : 3;  // operand size: 0=1 , 1=2 , 2=4 , 3=8, 4=16
-        insOpts _idInsOpt : 6;  // loongarch options for special: placeholders. e.g emitIns_R_C, also identifying the
-                                // accessing a local on stack.
-        unsigned _idLclVar : 1; // access a local on stack.
+            // TODO-LoongArch64: maybe delete on future.
+            opSize _idOpSize : 3; // operand size: 0=1 , 1=2 , 2=4 , 3=8, 4=16
+        insOpts    _idInsOpt : 6; // loongarch options for special: placeholders. e.g emitIns_R_C, also identifying the
+                                  // accessing a local on stack.
+        unsigned _idLclVar : 1;   // access a local on stack.
 #endif
 
 #ifdef TARGET_RISCV64
@@ -815,7 +816,7 @@ class emitter
         // x86:   46 bits
         // amd64: 46 bits
         // arm:   48 bits
-        // arm64: 49 bits
+        // arm64: 50 bits
         // loongarch64: 46 bits
 
         //
@@ -827,7 +828,7 @@ class emitter
 #if defined(TARGET_ARM)
 #define ID_EXTRA_BITFIELD_BITS (16)
 #elif defined(TARGET_ARM64)
-#define ID_EXTRA_BITFIELD_BITS (17)
+#define ID_EXTRA_BITFIELD_BITS (18)
 #elif defined(TARGET_XARCH) || defined(TARGET_LOONGARCH64) || defined(TARGET_RISCV64)
 #define ID_EXTRA_BITFIELD_BITS (14)
 #else
@@ -867,7 +868,7 @@ class emitter
         // x86:   52/48 bits
         // amd64: 53/48 bits
         // arm:   54/50 bits
-        // arm64: 56/51 bits
+        // arm64: 57/52 bits
         // loongarch64: 53/48 bits
         CLANG_FORMAT_COMMENT_ANCHOR;
 
@@ -885,7 +886,7 @@ class emitter
         // x86:   12/16 bits
         // amd64: 11/16 bits
         // arm:   10/14 bits
-        // arm64: 8/13 bits
+        // arm64: 7/12 bits
         // loongarch64: 11/16 bits
 
         unsigned _idSmallCns : ID_BIT_SMALL_CNS;
@@ -1432,6 +1433,16 @@ class emitter
         {
             _idLclVar = 1;
         }
+#ifdef TARGET_ARM64
+        bool idIsLclVarPair() const
+        {
+            return _idLclVarPair != 0;
+        }
+        void idSetIsLclVarPair()
+        {
+            _idLclVarPair = 1;
+        }
+#endif // TARGET_ARM64
 #endif // TARGET_ARMARCH
 
 #if defined(TARGET_ARM)
@@ -1819,6 +1830,22 @@ class emitter
 
 #endif // TARGET_XARCH
 
+#ifdef TARGET_ARM64
+    struct instrDescLclVarPair : instrDesc // contains 2 gc vars to be tracked
+    {
+        instrDescLclVarPair() = delete;
+
+        emitLclVarAddr iiaLclVar2;
+    };
+
+    struct instrDescLclVarPairCns : instrDescLclVarPair // contains 2 gc vars to be tracked, with large cons
+    {
+        instrDescLclVarPairCns() = delete;
+
+        cnsval_ssize_t idcCnsVal;
+    };
+#endif
+
     struct instrDescCGCA : instrDesc // call with ...
     {
         instrDescCGCA() = delete;
@@ -2600,7 +2627,26 @@ class emitter
 #endif // EMITTER_STATS
         return (instrDescLbl*)emitAllocAnyInstr(sizeof(instrDescLbl), EA_4BYTE);
     }
-#endif // !TARGET_ARM64
+#endif // TARGET_ARM64
+
+#if defined(TARGET_ARM64)
+    instrDescLclVarPair* emitAllocInstrLclVarPair(emitAttr attr)
+    {
+        instrDescLclVarPair* result = (instrDescLclVarPair*)emitAllocAnyInstr(sizeof(instrDescLclVarPair), attr);
+        result->idSetIsLclVarPair();
+        return result;
+    }
+
+    instrDescLclVarPairCns* emitAllocInstrLclVarPairCns(emitAttr attr, cnsval_size_t cns)
+    {
+        instrDescLclVarPairCns* result =
+            (instrDescLclVarPairCns*)emitAllocAnyInstr(sizeof(instrDescLclVarPairCns), attr);
+        result->idSetIsLargeCns();
+        result->idSetIsLclVarPair();
+        result->idcCnsVal = cns;
+        return result;
+    }
+#endif // TARGET_ARM64
 
     instrDescCns* emitAllocInstrCns(emitAttr attr)
     {
@@ -2686,6 +2732,8 @@ class emitter
 
 #if !defined(TARGET_ARM64)
     instrDescLbl* emitNewInstrLbl();
+#else
+    instrDescLclVarPair* emitNewInstrLclVarPair(emitAttr attr, cnsval_ssize_t cns);
 #endif // !TARGET_ARM64
 
     static const BYTE emitFmtToOps[];
@@ -3249,6 +3297,36 @@ inline emitter::instrDescLbl* emitter::emitNewInstrLbl()
 {
     return emitAllocInstrLbl();
 }
+#else
+inline emitter::instrDescLclVarPair* emitter::emitNewInstrLclVarPair(emitAttr attr, cnsval_ssize_t cns)
+{
+#if EMITTER_STATS
+    emitTotalIDescCnt++;
+    emitTotalIDescCnsCnt++;
+#endif // EMITTER_STATS
+
+    if (instrDesc::fitsInSmallCns(cns))
+    {
+        instrDescLclVarPair* id = emitAllocInstrLclVarPair(attr);
+        id->idSmallCns(cns);
+#if EMITTER_STATS
+        emitSmallCnsCnt++;
+        if ((cns - ID_MIN_SMALL_CNS) >= (SMALL_CNS_TSZ - 1))
+            emitSmallCns[SMALL_CNS_TSZ - 1]++;
+        else
+            emitSmallCns[cns - ID_MIN_SMALL_CNS]++;
+#endif
+        return id;
+    }
+    else
+    {
+        instrDescLclVarPairCns* id = emitAllocInstrLclVarPairCns(attr, cns);
+#if EMITTER_STATS
+        emitLargeCnsCnt++;
+#endif
+        return id;
+    }
+}
 #endif // !TARGET_ARM64
 
 inline emitter::instrDesc* emitter::emitNewInstrDsp(emitAttr attr, target_ssize_t dsp)
@@ -3329,10 +3407,22 @@ inline size_t emitter::emitGetInstrDescSize(const instrDesc* id)
     }
     else if (id->idIsLargeCns())
     {
+#ifdef TARGET_ARM64
+        if (id->idIsLclVarPair())
+        {
+            return sizeof(instrDescLclVarPairCns);
+        }
+#endif
         return sizeof(instrDescCns);
     }
     else
     {
+#ifdef TARGET_ARM64
+        if (id->idIsLclVarPair())
+        {
+            return sizeof(instrDescLclVarPair);
+        }
+#endif
         return sizeof(instrDesc);
     }
 }