JIT: Unroll more Equals/StartsWith/EndsWith on arm64 (dotnet#109036)

cshung · Nov 20, 2024 · db6cef1 · db6cef1
1 parent 2eb6a2a
commit db6cef1
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Showing 2 changed files with 13 additions and 6 deletions.
diff --git a/src/coreclr/jit/compiler.h b/src/coreclr/jit/compiler.h
@@ -9573,6 +9573,7 @@ class Compiler
         Memset,
         Memcpy,
         Memmove,
+        MemcmpU16,
         ProfiledMemmove,
         ProfiledMemcmp
     };
@@ -9649,6 +9650,14 @@ class Compiler
             threshold = maxRegSize * 4;
         }
 
+        if (type == UnrollKind::MemcmpU16)
+        {
+            threshold = maxRegSize * 2;
+#ifdef TARGET_ARM64
+            threshold = maxRegSize * 6;
+#endif
+        }
+
         // For profiled memcmp/memmove we don't want to unroll too much as it's just a guess,
         // and it works better for small sizes.
         if ((type == UnrollKind::ProfiledMemcmp) || (type == UnrollKind::ProfiledMemmove))

diff --git a/src/coreclr/jit/importervectorization.cpp b/src/coreclr/jit/importervectorization.cpp
@@ -6,8 +6,8 @@
 #pragma hdrstop
 #endif
 
-// For now the max possible size is Vector512<ushort>.Count * 2
-#define MaxPossibleUnrollSize 64
+// Overestimated threshold to avoid memory allocations,
+#define MaxPossibleUnrollSize 128
 
 //------------------------------------------------------------------------
 // importer_vectorization.cpp
@@ -484,9 +484,8 @@ GenTree* Compiler::impUtf16StringComparison(StringComparisonKind kind, CORINFO_S
             // We were unable to get the literal (e.g. dynamic context)
             return nullptr;
         }
-        if (cnsLength > (int)genTypeSize(roundDownMaxType(MaxPossibleUnrollSize * 2)))
+        if (cnsLength > ((int)getUnrollThreshold(MemcmpU16) / 2))
         {
-            // Not more than two loads (of max width)
             JITDUMP("UTF16 data is too long to unroll - bail out.\n");
             return nullptr;
         }
@@ -642,9 +641,8 @@ GenTree* Compiler::impUtf16SpanComparison(StringComparisonKind kind, CORINFO_SIG
             // We were unable to get the literal (e.g. dynamic context)
             return nullptr;
         }
-        if (cnsLength > (int)genTypeSize(roundDownMaxType(MaxPossibleUnrollSize * 2)))
+        if (cnsLength > ((int)getUnrollThreshold(MemcmpU16) / 2))
         {
-            // Not more than two loads (of max width)
             JITDUMP("UTF16 data is too long to unroll - bail out.\n");
             return nullptr;
         }