JIT: Unroll Equals and StartsWith for constant strings and spans. [0..32] chars

src/coreclr/jit/compiler.h

@@ -3014,6 +3014,7 @@ class Compiler
     // For binary opers.
     GenTree* gtNewOperNode(genTreeOps oper, var_types type, GenTree* op1, GenTree* op2);
 
+    GenTreeColon* gtNewColonNode(var_types type, GenTree* elseNode, GenTree* thenNode);
     GenTreeQmark* gtNewQmarkNode(var_types type, GenTree* cond, GenTreeColon* colon);
 
     GenTree* gtNewLargeOperNode(genTreeOps oper,
@@ -3023,6 +3024,9 @@ class Compiler
 
     GenTreeIntCon* gtNewIconNode(ssize_t value, var_types type = TYP_INT);
     GenTreeIntCon* gtNewIconNode(unsigned fieldOffset, FieldSeqNode* fieldSeq);
+    GenTreeIntCon* gtNull();
+    GenTreeIntCon* gtTrue();
+    GenTreeIntCon* gtFalse();
 
     GenTree* gtNewPhysRegNode(regNumber reg, var_types type);
 
@@ -4392,6 +4396,13 @@ class Compiler
     void impResetLeaveBlock(BasicBlock* block, unsigned jmpAddr);
     GenTree* impTypeIsAssignable(GenTree* typeTo, GenTree* typeFrom);
 
+    GenTree* impExpandHalfConstEqualsSWAR(GenTree* data, WCHAR* cns, int len, int dataOffset);
+    GenTree* impExpandHalfConstEqualsSIMD(GenTree* data, WCHAR* cns, int len, int dataOffset);
+    GenTree* impExpandHalfConstEquals(
+        GenTree* data, GenTree* lengthFld, bool checkForNull, bool startsWith, WCHAR* cnsData, int len, int dataOffset);
+    GenTreeStrCon* impGetStrConFromSpan(GenTree* span);
+    GenTree* impStringEqualsOrStartsWith(bool startsWith, CORINFO_SIG_INFO* sig, unsigned methodFlags);
+
     GenTree* impIntrinsic(GenTree*                newobjThis,
                           CORINFO_CLASS_HANDLE    clsHnd,
                           CORINFO_METHOD_HANDLE   method,
@@ -4508,7 +4519,7 @@ class Compiler
     void impInsertTreeBefore(GenTree* tree, const DebugInfo& di, Statement* stmtBefore);
     void impAssignTempGen(unsigned         tmp,
                           GenTree*         val,
-                          unsigned         curLevel,
+                          unsigned         curLevel   = (unsigned)CHECK_SPILL_NONE,
                           Statement**      pAfterStmt = nullptr,
                           const DebugInfo& di         = DebugInfo(),
                           BasicBlock*      block      = nullptr);

src/coreclr/jit/gentree.cpp

@@ -5685,6 +5685,11 @@ GenTree* Compiler::gtNewOperNode(genTreeOps oper, var_types type, GenTree* op1,
     return node;
 }
 
+GenTreeColon* Compiler::gtNewColonNode(var_types type, GenTree* elseNode, GenTree* thenNode)
+{
+    return new (this, GT_COLON) GenTreeColon(TYP_INT, elseNode, thenNode);
+}
+
 GenTreeQmark* Compiler::gtNewQmarkNode(var_types type, GenTree* cond, GenTreeColon* colon)
 {
     compQmarkUsed        = true;
@@ -5703,6 +5708,21 @@ GenTreeIntCon* Compiler::gtNewIconNode(ssize_t value, var_types type)
     return new (this, GT_CNS_INT) GenTreeIntCon(type, value);
 }
 
+GenTreeIntCon* Compiler::gtNull()
+{
+    return gtNewIconNode(0, TYP_REF);
+}
+
+GenTreeIntCon* Compiler::gtTrue()
+{
+    return gtNewIconNode(1, TYP_INT);
+}
+
+GenTreeIntCon* Compiler::gtFalse()
+{
+    return gtNewIconNode(0, TYP_INT);
+}
+
 GenTreeIntCon* Compiler::gtNewIconNode(unsigned fieldOffset, FieldSeqNode* fieldSeq)
 {
     GenTreeIntCon* node = new (this, GT_CNS_INT) GenTreeIntCon(TYP_I_IMPL, static_cast<ssize_t>(fieldOffset));