Improve codegen for Span/ReadOnlySpan indexer

GrabYourPitchforks · Mar 8, 2019 · d14b977 · d14b977
1 parent 24d05f5
commit d14b977
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Showing 2 changed files with 8 additions and 4 deletions.
diff --git a/src/jit/compiler.h b/src/jit/compiler.h
@@ -3423,7 +3423,7 @@ class Compiler
 
     static void impBashVarAddrsToI(GenTree* tree1, GenTree* tree2 = nullptr);
 
-    GenTree* impImplicitIorI4Cast(GenTree* tree, var_types dstTyp);
+    GenTree* impImplicitIorI4Cast(GenTree* tree, var_types dstTyp, bool zeroExtend = false);
 
     GenTree* impImplicitR4orR8Cast(GenTree* tree, var_types dstTyp);
 

diff --git a/src/jit/importer.cpp b/src/jit/importer.cpp
@@ -2946,9 +2946,13 @@ void Compiler::impBashVarAddrsToI(GenTree* tree1, GenTree* tree2)
  *  exist in the IL (at least on 64-bit where TYP_I_IMPL != TYP_INT) are
  *  turned into explicit casts here.
  *  We also allow an implicit conversion of a ldnull into a TYP_I_IMPL(0)
+ *  
+ *  If zeroExtend = false (default), if a non-const 32-bit input is
+ *  widened to 64 bits it will be sign-extended. If zeroExtend = true, it
+ *  will instead be zero-extended.
  */
 
-GenTree* Compiler::impImplicitIorI4Cast(GenTree* tree, var_types dstTyp)
+GenTree* Compiler::impImplicitIorI4Cast(GenTree* tree, var_types dstTyp, bool zeroExtend)
 {
     var_types currType   = genActualType(tree->gtType);
     var_types wantedType = genActualType(dstTyp);
@@ -2967,7 +2971,7 @@ GenTree* Compiler::impImplicitIorI4Cast(GenTree* tree, var_types dstTyp)
         else if (varTypeIsI(wantedType) && (currType == TYP_INT))
         {
             // Note that this allows TYP_INT to be cast to a TYP_I_IMPL when wantedType is a TYP_BYREF or TYP_REF
-            tree = gtNewCastNode(TYP_I_IMPL, tree, false, TYP_I_IMPL);
+            tree = gtNewCastNode(TYP_I_IMPL, tree, zeroExtend /* fromUnsigned */, TYP_I_IMPL);
         }
         else if ((wantedType == TYP_INT) && varTypeIsI(currType))
         {
@@ -3885,7 +3889,7 @@ GenTree* Compiler::impIntrinsic(GenTree*                newobjThis,
                 GenTreeBoundsChk(GT_ARR_BOUNDS_CHECK, TYP_VOID, index, length, SCK_RNGCHK_FAIL);
 
             // Element access
-            GenTree*             indexIntPtr = impImplicitIorI4Cast(indexClone, TYP_I_IMPL);
+            GenTree*             indexIntPtr = impImplicitIorI4Cast(indexClone, TYP_I_IMPL, true /* zeroExtend */);
             GenTree*             sizeofNode  = gtNewIconNode(elemSize);
             GenTree*             mulNode     = gtNewOperNode(GT_MUL, TYP_I_IMPL, indexIntPtr, sizeofNode);
             CORINFO_FIELD_HANDLE ptrHnd      = info.compCompHnd->getFieldInClass(clsHnd, 0);