[Strings] Remove stringview types and instructions (#6579)

The stringview types from the stringref proposal have three irregularities that
break common invariants and require pervasive special casing to handle properly:
they are supertypes of `none` but not subtypes of `any`, they cannot be the
targets of casts, and they cannot be used to construct nullable references. At
the same time, the stringref proposal has been superseded by the imported
strings proposal, which does not have these irregularities. The cost of
maintaing and improving our support for stringview types is no longer worth the
benefit of supporting them.

Simplify the code base by entirely removing the stringview types and related
instructions that do not have analogues in the imported strings proposal and do
not make sense in the absense of stringviews.

Three remaining instructions, `stringview_wtf16.get_codeunit`,
`stringview_wtf16.slice`, and `stringview_wtf16.length` take stringview operands
in the stringref proposal but cannot be removed because they lower to operations
from the imported strings proposal. These instructions are changed to take
stringref operands in Binaryen IR, and to allow a graceful upgrade path for
users of these instructions, the text and binary parsers still accept but ignore
`string.as_wtf16`, which is the instruction used to convert stringrefs to
stringviews. The binary writer emits code sequences that use scratch locals and `string.as_wtf16` to keep the output valid.

Future PRs will further align binaryen with the imported strings proposal
instead of the stringref proposal, for example by making `string` a subtype of
`extern` instead of a subtype of `any` and by removing additional instructions
that do not have analogues in the imported strings proposal.

1 files changed, 0 insertions, 81 deletions

diff --git a/src/binaryen-c.h b/src/binaryen-c.h
index 595086d6a..f01b4c3be 100644
--- a/src/binaryen-c.h
+++ b/src/binaryen-c.h
@@ -107,9 +107,6 @@ BINARYEN_API BinaryenType BinaryenTypeI31ref(void);
 BINARYEN_API BinaryenType BinaryenTypeStructref(void);
 BINARYEN_API BinaryenType BinaryenTypeArrayref(void);
 BINARYEN_API BinaryenType BinaryenTypeStringref(void);
-BINARYEN_API BinaryenType BinaryenTypeStringviewWTF8(void);
-BINARYEN_API BinaryenType BinaryenTypeStringviewWTF16(void);
-BINARYEN_API BinaryenType BinaryenTypeStringviewIter(void);
 BINARYEN_API BinaryenType BinaryenTypeNullref(void);
 BINARYEN_API BinaryenType BinaryenTypeNullExternref(void);
 BINARYEN_API BinaryenType BinaryenTypeNullFuncref(void);
@@ -149,9 +146,6 @@ BINARYEN_API BinaryenHeapType BinaryenHeapTypeI31(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeStruct(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeArray(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeString(void);
-BINARYEN_API BinaryenHeapType BinaryenHeapTypeStringviewWTF8(void);
-BINARYEN_API BinaryenHeapType BinaryenHeapTypeStringviewWTF16(void);
-BINARYEN_API BinaryenHeapType BinaryenHeapTypeStringviewIter(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeNone(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeNoext(void);
 BINARYEN_API BinaryenHeapType BinaryenHeapTypeNofunc(void);
@@ -701,7 +695,6 @@ BINARYEN_API BinaryenOp BinaryenStringMeasureUTF8(void);
 BINARYEN_API BinaryenOp BinaryenStringMeasureWTF8(void);
 BINARYEN_API BinaryenOp BinaryenStringMeasureWTF16(void);
 BINARYEN_API BinaryenOp BinaryenStringMeasureIsUSV(void);
-BINARYEN_API BinaryenOp BinaryenStringMeasureWTF16View(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeUTF8(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeLossyUTF8(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeWTF8(void);
@@ -710,13 +703,6 @@ BINARYEN_API BinaryenOp BinaryenStringEncodeUTF8Array(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeLossyUTF8Array(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeWTF8Array(void);
 BINARYEN_API BinaryenOp BinaryenStringEncodeWTF16Array(void);
-BINARYEN_API BinaryenOp BinaryenStringAsWTF8(void);
-BINARYEN_API BinaryenOp BinaryenStringAsWTF16(void);
-BINARYEN_API BinaryenOp BinaryenStringAsIter(void);
-BINARYEN_API BinaryenOp BinaryenStringIterMoveAdvance(void);
-BINARYEN_API BinaryenOp BinaryenStringIterMoveRewind(void);
-BINARYEN_API BinaryenOp BinaryenStringSliceWTF8(void);
-BINARYEN_API BinaryenOp BinaryenStringSliceWTF16(void);
 BINARYEN_API BinaryenOp BinaryenStringEqEqual(void);
 BINARYEN_API BinaryenOp BinaryenStringEqCompare(void);
 
@@ -1130,9 +1116,6 @@ BinaryenStringEq(BinaryenModuleRef module,
                  BinaryenOp op,
                  BinaryenExpressionRef left,
                  BinaryenExpressionRef right);
-BINARYEN_API BinaryenExpressionRef BinaryenStringAs(BinaryenModuleRef module,
-                                                    BinaryenOp op,
-                                                    BinaryenExpressionRef ref);
 BINARYEN_API BinaryenExpressionRef
 BinaryenStringWTF8Advance(BinaryenModuleRef module,
                           BinaryenExpressionRef ref,
@@ -1151,7 +1134,6 @@ BinaryenStringIterMove(BinaryenModuleRef module,
                        BinaryenExpressionRef num);
 BINARYEN_API BinaryenExpressionRef
 BinaryenStringSliceWTF(BinaryenModuleRef module,
-                       BinaryenOp op,
                        BinaryenExpressionRef ref,
                        BinaryenExpressionRef start,
                        BinaryenExpressionRef end);
@@ -2619,34 +2601,6 @@ BinaryenStringEqGetRight(BinaryenExpressionRef expr);
 BINARYEN_API void BinaryenStringEqSetRight(BinaryenExpressionRef expr,
                                            BinaryenExpressionRef rightExpr);
 
-// StringAs
-
-BINARYEN_API BinaryenOp BinaryenStringAsGetOp(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringAsSetOp(BinaryenExpressionRef expr,
-                                        BinaryenOp op);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringAsGetRef(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringAsSetRef(BinaryenExpressionRef expr,
-                                         BinaryenExpressionRef refExpr);
-
-// StringWTF8Advance
-
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringWTF8AdvanceGetRef(BinaryenExpressionRef expr);
-BINARYEN_API void
-BinaryenStringWTF8AdvanceSetRef(BinaryenExpressionRef expr,
-                                BinaryenExpressionRef refExpr);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringWTF8AdvanceGetPos(BinaryenExpressionRef expr);
-BINARYEN_API void
-BinaryenStringWTF8AdvanceSetPos(BinaryenExpressionRef expr,
-                                BinaryenExpressionRef posExpr);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringWTF8AdvanceGetBytes(BinaryenExpressionRef expr);
-BINARYEN_API void
-BinaryenStringWTF8AdvanceSetBytes(BinaryenExpressionRef expr,
-                                  BinaryenExpressionRef bytesExpr);
-
 // StringWTF16Get
 
 BINARYEN_API BinaryenExpressionRef
@@ -2658,32 +2612,8 @@ BinaryenStringWTF16GetGetPos(BinaryenExpressionRef expr);
 BINARYEN_API void BinaryenStringWTF16GetSetPos(BinaryenExpressionRef expr,
                                                BinaryenExpressionRef posExpr);
 
-// StringIterNext
-
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringIterNextGetRef(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringIterNextSetRef(BinaryenExpressionRef expr,
-                                               BinaryenExpressionRef refExpr);
-
-// StringIterMove
-
-BINARYEN_API BinaryenOp BinaryenStringIterMoveGetOp(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringIterMoveSetOp(BinaryenExpressionRef expr,
-                                              BinaryenOp op);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringIterMoveGetRef(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringIterMoveSetRef(BinaryenExpressionRef expr,
-                                               BinaryenExpressionRef refExpr);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringIterMoveGetNum(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringIterMoveSetNum(BinaryenExpressionRef expr,
-                                               BinaryenExpressionRef numExpr);
-
 // StringSliceWTF
 
-BINARYEN_API BinaryenOp BinaryenStringSliceWTFGetOp(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringSliceWTFSetOp(BinaryenExpressionRef expr,
-                                              BinaryenOp op);
 BINARYEN_API BinaryenExpressionRef
 BinaryenStringSliceWTFGetRef(BinaryenExpressionRef expr);
 BINARYEN_API void BinaryenStringSliceWTFSetRef(BinaryenExpressionRef expr,
@@ -2698,17 +2628,6 @@ BinaryenStringSliceWTFGetEnd(BinaryenExpressionRef expr);
 BINARYEN_API void BinaryenStringSliceWTFSetEnd(BinaryenExpressionRef expr,
                                                BinaryenExpressionRef endExpr);
 
-// StringSliceIter
-
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringSliceIterGetRef(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringSliceIterSetRef(BinaryenExpressionRef expr,
-                                                BinaryenExpressionRef refExpr);
-BINARYEN_API BinaryenExpressionRef
-BinaryenStringSliceIterGetNum(BinaryenExpressionRef expr);
-BINARYEN_API void BinaryenStringSliceIterSetNum(BinaryenExpressionRef expr,
-                                                BinaryenExpressionRef numExpr);
-
 // Functions
 
 BINARYEN_REF(Function);