Merge pull request #18891 from CarolEidt/Fix18153

Ensure BuildUse uses the correct reg number

1 files changed, 44 insertions, 0 deletions

diff --git a/src/jit/gentree.h b/src/jit/gentree.h
index 3bddf61077..83f07d3213 100644
--- a/src/jit/gentree.h
+++ b/src/jit/gentree.h
@@ -1721,6 +1721,9 @@ public:
     // Returns true if it is a node returning its value in more than one register
     inline bool IsMultiRegNode() const;
 
+    // Returns the regIndex'th register defined by a possibly-multireg node.
+    regNumber GetRegByIndex(int regIndex);
+
     // Returns true if it is a GT_COPY or GT_RELOAD node
     inline bool IsCopyOrReload() const;
 
@@ -6006,6 +6009,47 @@ inline bool GenTree::IsMultiRegNode() const
     return false;
 }
 
+//-----------------------------------------------------------------------------------
+// GetRegByIndex: Get a specific register, based on regIndex, that is produced
+//                by this node.
+//
+// Arguments:
+//     regIndex - which register to return (must be 0 for non-multireg nodes)
+//
+// Return Value:
+//     The register, if any, assigned to this index for this node.
+//
+inline regNumber GenTree::GetRegByIndex(int regIndex)
+{
+    if (regIndex == 0)
+    {
+        return gtRegNum;
+    }
+    if (IsMultiRegCall())
+    {
+        return AsCall()->GetRegNumByIdx(regIndex);
+    }
+
+#if FEATURE_ARG_SPLIT
+    if (OperIsPutArgSplit())
+    {
+        return AsPutArgSplit()->GetRegNumByIdx(regIndex);
+    }
+#endif
+#if defined(_TARGET_ARM_)
+    if (OperIsMultiRegOp())
+    {
+        return AsMultiRegOp()->GetRegNumByIdx(regIndex);
+    }
+    if (OperIs(GT_COPY, GT_RELOAD))
+    {
+        return AsCopyOrReload()->GetRegNumByIdx(regIndex);
+    }
+#endif
+    assert(!"Invalid regIndex for GetRegFromMultiRegNode");
+    return REG_NA;
+}
+
 //-------------------------------------------------------------------------
 // IsCopyOrReload: whether this is a GT_COPY or GT_RELOAD node.
 //