JIT: Intrinsify UTF16->UTF8 conversion for string literals (Encoding.UTF8.TryGetBytes) (#85328)

Co-authored-by: Jakob Botsch Nielsen <[email protected]>

Author: EgorBo

src/coreclr/jit/compiler.cpp

@@ -4877,6 +4877,7 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
         bool doBranchOpt               = true;
         bool doCse                     = true;
         bool doAssertionProp           = true;
+        bool doVNBasedIntrinExpansion  = true;
         bool doRangeAnalysis           = true;
         bool doVNBasedDeadStoreRemoval = true;
         int  iterations                = 1;
@@ -4890,6 +4891,7 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
         doBranchOpt               = doValueNum && (JitConfig.JitDoRedundantBranchOpts() != 0);
         doCse                     = doValueNum;
         doAssertionProp           = doValueNum && (JitConfig.JitDoAssertionProp() != 0);
+        doVNBasedIntrinExpansion  = doValueNum;
         doRangeAnalysis           = doAssertionProp && (JitConfig.JitDoRangeAnalysis() != 0);
         doVNBasedDeadStoreRemoval = doValueNum && (JitConfig.JitDoVNBasedDeadStoreRemoval() != 0);
 
@@ -4973,6 +4975,13 @@ void Compiler::compCompile(void** methodCodePtr, uint32_t* methodCodeSize, JitFl
                 DoPhase(this, PHASE_ASSERTION_PROP_MAIN, &Compiler::optAssertionPropMain);
             }
 
+            if (doVNBasedIntrinExpansion)
+            {
+                // Expand some intrinsics based on VN data
+                //
+                DoPhase(this, PHASE_VN_BASED_INTRINSIC_EXPAND, &Compiler::fgVNBasedIntrinsicExpansion);
+            }
+
             if (doRangeAnalysis)
             {
                 // Bounds check elimination via range analysis

src/coreclr/jit/compiler.h

@@ -5214,6 +5214,8 @@ class Compiler
         }
     }
 
+    bool GetObjectHandleAndOffset(GenTree* tree, ssize_t* byteOffset, CORINFO_OBJECT_HANDLE* pObj);
+
     // Convert a BYTE which represents the VM's CorInfoGCtype to the JIT's var_types
     var_types getJitGCType(BYTE gcType);
 
@@ -5357,6 +5359,10 @@ class Compiler
     PhaseStatus fgExpandStaticInit();
     bool fgExpandStaticInitForCall(BasicBlock** pBlock, Statement* stmt, GenTreeCall* call);
 
+    PhaseStatus fgVNBasedIntrinsicExpansion();
+    bool fgVNBasedIntrinsicExpansionForCall(BasicBlock** pBlock, Statement* stmt, GenTreeCall* call);
+    bool fgVNBasedIntrinsicExpansionForCall_ReadUtf8(BasicBlock** pBlock, Statement* stmt, GenTreeCall* call);
+
     PhaseStatus fgInsertGCPolls();
     BasicBlock* fgCreateGCPoll(GCPollType pollType, BasicBlock* block);
 
@@ -7087,6 +7093,7 @@ class Compiler
 #define OMF_HAS_MDARRAYREF                     0x00004000 // Method contains multi-dimensional intrinsic array element loads or stores.
 #define OMF_HAS_STATIC_INIT                    0x00008000 // Method has static initializations we might want to partially inline
 #define OMF_HAS_TLS_FIELD                      0x00010000 // Method contains TLS field access
+#define OMF_HAS_SPECIAL_INTRINSICS             0x00020000 // Method contains special intrinsics expanded in late phases
 
     // clang-format on
 
@@ -7147,6 +7154,16 @@ class Compiler
         optMethodFlags |= OMF_HAS_TLS_FIELD;
     }
 
+    bool doesMethodHaveSpecialIntrinsics()
+    {
+        return (optMethodFlags & OMF_HAS_SPECIAL_INTRINSICS) != 0;
+    }
+
+    void setMethodHasSpecialIntrinsics()
+    {
+        optMethodFlags |= OMF_HAS_SPECIAL_INTRINSICS;
+    }
+
     void pickGDV(GenTreeCall*           call,
                  IL_OFFSET              ilOffset,
                  bool                   isInterface,
@@ -8947,7 +8964,7 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
 
 public:
     // Similar to roundUpSIMDSize, but for General Purpose Registers (GPR)
-    unsigned int roundUpGPRSize(unsigned size)
+    unsigned roundUpGPRSize(unsigned size)
     {
         if (size > 4 && (REGSIZE_BYTES == 8))
         {
@@ -8960,6 +8977,33 @@ XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
         return size; // 2, 1, 0
     }
 
+    var_types roundDownMaxType(unsigned size)
+    {
+        assert(size > 0);
+        var_types result = TYP_UNDEF;
+#ifdef FEATURE_SIMD
+        if (IsBaselineSimdIsaSupported() && (roundDownSIMDSize(size) > 0))
+        {
+            return getSIMDTypeForSize(roundDownSIMDSize(size));
+        }
+#endif
+        int nearestPow2 = 1 << BitOperations::Log2((unsigned)size);
+        switch (min(nearestPow2, REGSIZE_BYTES))
+        {
+            case 1:
+                return TYP_UBYTE;
+            case 2:
+                return TYP_USHORT;
+            case 4:
+                return TYP_INT;
+            case 8:
+                assert(REGSIZE_BYTES == 8);
+                return TYP_LONG;
+            default:
+                unreached();
+        }
+    }
+
     enum UnrollKind
     {
         Memset,

src/coreclr/jit/compphases.h

@@ -86,6 +86,7 @@ CompPhaseNameMacro(PHASE_VALUE_NUMBER,               "Do value numbering",
 CompPhaseNameMacro(PHASE_OPTIMIZE_INDEX_CHECKS,      "Optimize index checks",          false, -1, false)
 CompPhaseNameMacro(PHASE_OPTIMIZE_VALNUM_CSES,       "Optimize Valnum CSEs",           false, -1, false)
 CompPhaseNameMacro(PHASE_VN_COPY_PROP,               "VN based copy prop",             false, -1, false)
+CompPhaseNameMacro(PHASE_VN_BASED_INTRINSIC_EXPAND,  "VN based intrinsic expansion",   false, -1, false)
 CompPhaseNameMacro(PHASE_OPTIMIZE_BRANCHES,          "Redundant branch opts",          false, -1, false)
 CompPhaseNameMacro(PHASE_ASSERTION_PROP_MAIN,        "Assertion prop",                 false, -1, false)
 CompPhaseNameMacro(PHASE_IF_CONVERSION,              "If conversion",                  false, -1, false)