[PATCH] D79806: [CodeGen] Specify meaning of ISD opcodes for scalable vectors

[Sander de Smalen via Phabricator via llvm-commits]

sdesmalen updated this revision to Diff 265769.
sdesmalen added a comment.

- Added clarification that extract_subvector does not support extracting a scalable vector from a fixed-width vector (and similar for insert_subvector).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D79806/new/

https://reviews.llvm.org/D79806

Files:
  llvm/include/llvm/CodeGen/ISDOpcodes.h


Index: llvm/include/llvm/CodeGen/ISDOpcodes.h
===================================================================
--- llvm/include/llvm/CodeGen/ISDOpcodes.h
+++ llvm/include/llvm/CodeGen/ISDOpcodes.h
@@ -445,44 +445,59 @@
   /// Returns platform specific canonical encoding of a floating point number.
   FCANONICALIZE,
 
-  /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a vector with the
-  /// specified, possibly variable, elements.  The number of elements is
-  /// required to be a power of two.  The types of the operands must all be
-  /// the same and must match the vector element type, except that integer
-  /// types are allowed to be larger than the element type, in which case
-  /// the operands are implicitly truncated.
+  /// BUILD_VECTOR(ELT0, ELT1, ELT2, ELT3,...) - Return a fixed-width vector
+  /// with the specified, possibly variable, elements.  The number of elements
+  /// is required to be a power of two. The types of the operands must all be
+  /// the same and must match the vector element type, except that integer types
+  /// are allowed to be larger than the element type, in which case the operands
+  /// are implicitly truncated.
   BUILD_VECTOR,
 
   /// INSERT_VECTOR_ELT(VECTOR, VAL, IDX) - Returns VECTOR with the element
-  /// at IDX replaced with VAL.  If the type of VAL is larger than the vector
-  /// element type then VAL is truncated before replacement.
+  /// at IDX replaced with VAL. If the type of VAL is larger than the vector
+  /// element type then VAL is truncated before replacement. If VECTOR is a
+  /// scalable vector, then IDX is not first scaled by the runtime scaling
+  /// factor of VECTOR. If VECTOR is a scalable vector and IDX is a constant
+  /// value, then IDX may be larger than the minimum vector width.
   INSERT_VECTOR_ELT,
 
   /// EXTRACT_VECTOR_ELT(VECTOR, IDX) - Returns a single element from VECTOR
-  /// identified by the (potentially variable) element number IDX.  If the
-  /// return type is an integer type larger than the element type of the
-  /// vector, the result is extended to the width of the return type. In
-  /// that case, the high bits are undefined.
+  /// identified by the (potentially variable) element number IDX. If the return
+  /// type is an integer type larger than the element type of the vector, the
+  /// result is extended to the width of the return type. In that case, the high
+  /// bits are undefined. If VECTOR is a scalable vector, then IDX is not first
+  /// scaled by the runtime scaling factor of VECTOR. If VECTOR is a scalable
+  /// vector and IDX is a constant value, then IDX may be larger than the
+  /// minimum vector width.
   EXTRACT_VECTOR_ELT,
 
   /// CONCAT_VECTORS(VECTOR0, VECTOR1, ...) - Given a number of values of
   /// vector type with the same length and element type, this produces a
   /// concatenated vector result value, with length equal to the sum of the
-  /// lengths of the input vectors.
+  /// lengths of the input vectors. If VECTOR0 is a fixed-width vector, then
+  /// VECTOR1..VECTORN must all be fixed-width vectors. Similarly, if VECTOR0
+  /// is a scalable vector, then VECTOR1..VECTORN must all be scalable vectors.
   CONCAT_VECTORS,
 
-  /// INSERT_SUBVECTOR(VECTOR1, VECTOR2, IDX) - Returns a vector
-  /// with VECTOR2 inserted into VECTOR1 at the constant element number
-  /// IDX, which must be a multiple of the VECTOR2 vector length. The
-  /// elements of VECTOR1 starting at IDX are overwritten with VECTOR2.
-  /// Elements IDX through vector_length(VECTOR2) must be valid VECTOR1
-  /// indices.
+  /// INSERT_SUBVECTOR(VECTOR1, VECTOR2, IDX) - Returns a vector with VECTOR2
+  /// inserted into VECTOR1. Let the type of VECTOR2 be T, then IDX is first
+  /// scaled by the same runtime scaling factor of T to form IDX_0, which
+  /// represents the starting element number at which VECTOR2 will be
+  /// inserted. The elements of VECTOR1 starting at IDX_0 are overwritten with
+  /// VECTOR2. Elements IDX_0 through (IDX_0 + vector_length(VECTOR2) - 1)
+  /// must be valid VECTOR1 indices.
+  /// IDX must be a constant multiple of T's known minimum vector length.
+  /// This operation supports inserting a fixed-width vector into a
+  /// scalable vector, but not the other way around.
   INSERT_SUBVECTOR,
 
-  /// EXTRACT_SUBVECTOR(VECTOR, IDX) - Returns a subvector from VECTOR (an
-  /// vector value) starting with the constant element number IDX, which
-  /// must be a multiple of the result vector length. Elements IDX through
-  /// vector_length(VECTOR) must be valid VECTOR indices.
+  /// EXTRACT_SUBVECTOR(VECTOR, IDX) - Returns a subvector from VECTOR.
+  /// Let the result type be T, then IDX is first scaled by the same runtime
+  /// scaling factor of T. The resulting index represents the starting
+  /// element number from which a subvector of type T is extracted.
+  /// IDX must be a constant multiple of T's known minimum vector length.
+  /// This operation supports extracting a fixed-width vector from a
+  /// scalable vector, but not the other way around.
   EXTRACT_SUBVECTOR,
 
   /// VECTOR_SHUFFLE(VEC1, VEC2) - Returns a vector, of the same type as


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