[WebAssembly] Define a new "Lime1" CPU

First, define some new target features. These are subsets of existing features
that reflect implemenetation concerns:

 - "call-indirect-overlong" - implied by "reference-types"; just the overlong
   encoding for the `call_indirect` immediate, and not the actual reference
   types.

 - "bulk-memory-opt" - implied by "bulk-memory": just `memory.copy` and
   `memory.fill`, and not the other instructions in the bulk-memory
    proposal.

Next, define a new target CPU, "Lime1", which enables mutable-globals,
bulk-memory-opt, multivalue, sign-ext, nontrapping-fptoint, extended-const,
and call-indirect-overlong. Unlike the default "generic" CPU, "lime1" is meant
to be frozen, and followed up by "lime2" and so on when new features are
desired.

Author: sunfishcode

clang/lib/Basic/Targets/WebAssembly.cpp

@@ -47,6 +47,8 @@ bool WebAssemblyTargetInfo::hasFeature(StringRef Feature) const {
   return llvm::StringSwitch<bool>(Feature)
       .Case("atomics", HasAtomics)
       .Case("bulk-memory", HasBulkMemory)
+      .Case("bulk-memory-opt", HasBulkMemoryOpt)
+      .Case("call-indirect-overlong", HasCallIndirectOverlong)
       .Case("exception-handling", HasExceptionHandling)
       .Case("extended-const", HasExtendedConst)
       .Case("fp16", HasFP16)
@@ -79,6 +81,8 @@ void WebAssemblyTargetInfo::getTargetDefines(const LangOptions &Opts,
     Builder.defineMacro("__wasm_atomics__");
   if (HasBulkMemory)
     Builder.defineMacro("__wasm_bulk_memory__");
+  if (HasBulkMemoryOpt)
+    Builder.defineMacro("__wasm_bulk_memory_opt__");
   if (HasExceptionHandling)
     Builder.defineMacro("__wasm_exception_handling__");
   if (HasExtendedConst)
@@ -155,12 +159,23 @@ bool WebAssemblyTargetInfo::initFeatureMap(
     const std::vector<std::string> &FeaturesVec) const {
   auto addGenericFeatures = [&]() {
     Features["bulk-memory"] = true;
+    Features["bulk-memory-opt"] = true;
+    Features["call-indirect-overlong"] = true;
     Features["multivalue"] = true;
     Features["mutable-globals"] = true;
     Features["nontrapping-fptoint"] = true;
     Features["reference-types"] = true;
     Features["sign-ext"] = true;
   };
+  auto addLime1Features = [&]() {
+    Features["multivalue"] = true;
+    Features["mutable-globals"] = true;
+    Features["call-indirect-overlong"] = true;
+    Features["sign-ext"] = true;
+    Features["bulk-memory-opt"] = true;
+    Features["nontrapping-fptoint"] = true;
+    Features["extended-const"] = true;
+  };
   auto addBleedingEdgeFeatures = [&]() {
     addGenericFeatures();
     Features["atomics"] = true;
@@ -174,6 +189,8 @@ bool WebAssemblyTargetInfo::initFeatureMap(
   };
   if (CPU == "generic") {
     addGenericFeatures();
+  } else if (CPU == "lime1") {
+    addLime1Features();
   } else if (CPU == "bleeding-edge") {
     addBleedingEdgeFeatures();
   }
@@ -200,6 +217,14 @@ bool WebAssemblyTargetInfo::handleTargetFeatures(
       HasBulkMemory = false;
       continue;
     }
+    if (Feature == "+bulk-memory-opt") {
+      HasBulkMemoryOpt = true;
+      continue;
+    }
+    if (Feature == "-bulk-memory-opt") {
+      HasBulkMemoryOpt = false;
+      continue;
+    }
     if (Feature == "+exception-handling") {
       HasExceptionHandling = true;
       continue;
@@ -265,6 +290,14 @@ bool WebAssemblyTargetInfo::handleTargetFeatures(
       HasReferenceTypes = false;
       continue;
     }
+    if (Feature == "+call-indirect-overlong") {
+      HasCallIndirectOverlong = true;
+      continue;
+    }
+    if (Feature == "-call-indirect-overlong") {
+      HasCallIndirectOverlong = false;
+      continue;
+    }
     if (Feature == "+relaxed-simd") {
       SIMDLevel = std::max(SIMDLevel, RelaxedSIMD);
       continue;
@@ -310,6 +343,18 @@ bool WebAssemblyTargetInfo::handleTargetFeatures(
         << Feature << "-target-feature";
     return false;
   }
+
+  // The reference-types feature included the change to `call_indirect`
+  // encodings to support overlong immediates.
+  if (HasReferenceTypes) {
+    HasCallIndirectOverlong = true;
+  }
+
+  // bulk-memory-opt is a subset of bulk-memory.
+  if (HasBulkMemory) {
+    HasBulkMemoryOpt = true;
+  }
+
   return true;
 }
 

clang/lib/Basic/Targets/WebAssembly.h

@@ -55,6 +55,7 @@ class LLVM_LIBRARY_VISIBILITY WebAssemblyTargetInfo : public TargetInfo {
 
   bool HasAtomics = false;
   bool HasBulkMemory = false;
+  bool HasBulkMemoryOpt = false;
   bool HasExceptionHandling = false;
   bool HasExtendedConst = false;
   bool HasFP16 = false;
@@ -63,6 +64,7 @@ class LLVM_LIBRARY_VISIBILITY WebAssemblyTargetInfo : public TargetInfo {
   bool HasMutableGlobals = false;
   bool HasNontrappingFPToInt = false;
   bool HasReferenceTypes = false;
+  bool HasCallIndirectOverlong = false;
   bool HasSignExt = false;
   bool HasTailCall = false;
   bool HasWideArithmetic = false;

lld/test/wasm/compress-relocs.ll

@@ -1,5 +1,5 @@
 ; RUN: llc -filetype=obj %s -o %t.o
-; RUN: llvm-mc -mattr=+reference-types -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/call-indirect.s -o %t2.o
+; RUN: llvm-mc -mattr=+call-indirect-overlong -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/call-indirect.s -o %t2.o
 ; RUN: wasm-ld --export-dynamic -o %t.wasm %t2.o %t.o
 ; RUN: obj2yaml %t.wasm | FileCheck %s
 ; RUN: wasm-ld --export-dynamic -O2 -o %t-opt.wasm %t2.o %t.o

lld/test/wasm/import-table-explicit.s

@@ -1,4 +1,4 @@
-# RUN: llvm-mc -mattr=+reference-types -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
+# RUN: llvm-mc -mattr=+call-indirect-overlong -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o
 # RUN: wasm-ld --import-table -o %t.wasm %t.o
 # RUN: obj2yaml %t.wasm | FileCheck %s
 

lld/test/wasm/invalid-mvp-table-use.s

@@ -1,7 +1,7 @@
 # RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
 #
 # If any table is defined or declared besides the __indirect_function_table,
-# the compilation unit should be compiled with -mattr=+reference-types,
+# the compilation unit should be compiled with -mattr=+call-indirect-overlong,
 # causing symbol table entries to be emitted for all tables.
 # RUN: not wasm-ld --no-entry %t.o -o %t.wasm 2>&1 | FileCheck -check-prefix=CHECK-ERR %s
 

lld/test/wasm/lto/Inputs/libcall-archive.ll

@@ -5,4 +5,4 @@ define void @memcpy() #0 {
   ret void
 }
 
-attributes #0 = { "target-features"="-bulk-memory" }
+attributes #0 = { "target-features"="-bulk-memory,-bulk-memory-opt" }

lld/test/wasm/lto/libcall-archive.ll

@@ -16,7 +16,7 @@ entry:
 
 declare void @llvm.memcpy.p0.p0.i64(ptr nocapture, ptr nocapture, i64, i1)
 
-attributes #0 = { "target-features"="-bulk-memory" }
+attributes #0 = { "target-features"="-bulk-memory,-bulk-memory-opt" }
 
 ; CHECK:       - Type:            CUSTOM
 ; CHECK-NEXT:    Name:            name

lld/test/wasm/lto/stub-library-libcall.s

@@ -2,7 +2,7 @@
 # RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t_main.o %t/main.s
 # RUN: llvm-as %S/Inputs/foo.ll -o %t_foo.o
 # RUN: llvm-as %S/Inputs/libcall.ll -o %t_libcall.o
-# RUN: wasm-ld -mllvm -mattr=-bulk-memory %t_main.o %t_libcall.o %t_foo.o %p/Inputs/stub.so -o %t.wasm
+# RUN: wasm-ld -mllvm -mattr=-bulk-memory,-bulk-memory-opt %t_main.o %t_libcall.o %t_foo.o %p/Inputs/stub.so -o %t.wasm
 # RUN: obj2yaml %t.wasm | FileCheck %s
 
 # The function `func_with_libcall` will generate an undefined reference to
@@ -12,7 +12,7 @@
 # If %t_foo.o is not included in the link we get an undefined symbol reported
 # to the dependency of memcpy on the foo export:
 
-# RUN: not wasm-ld -mllvm -mattr=-bulk-memory %t_main.o %t_libcall.o %p/Inputs/stub.so -o %t.wasm 2>&1 | FileCheck --check-prefix=MISSING %s
+# RUN: not wasm-ld -mllvm -mattr=-bulk-memory,-bulk-memory-opt %t_main.o %t_libcall.o %p/Inputs/stub.so -o %t.wasm 2>&1 | FileCheck --check-prefix=MISSING %s
 # MISSING: stub.so: undefined symbol: foo. Required by memcpy
 
 #--- main.s

lld/test/wasm/multi-table.s

@@ -26,7 +26,7 @@ call_indirect_explicit_tables:
   call_indirect table_b, () -> ()
   end_function
 
-# RT-MVP: wasm-ld: error: object file not built with 'reference-types' feature conflicts with import of table table_a by file
+# RT-MVP: wasm-ld: error: object file not built with 'call-indirect-overlong' feature conflicts with import of table table_a by file
 
 # CHECK:      --- !WASM
 # CHECK-NEXT: FileHeader:

lld/wasm/InputFiles.cpp

@@ -248,10 +248,11 @@ static void setRelocs(const std::vector<T *> &chunks,
   }
 }
 
-// An object file can have two approaches to tables.  With the reference-types
-// feature enabled, input files that define or use tables declare the tables
-// using symbols, and record each use with a relocation.  This way when the
-// linker combines inputs, it can collate the tables used by the inputs,
+// An object file can have two approaches to tables.  With the
+// call-indirect-overlong feature enabled (explicitly, or implied by the
+// reference-types feature), input files that define or use tables declare the
+// tables using symbols, and record each use with a relocation.  This way when
+// the linker combines inputs, it can collate the tables used by the inputs,
 // assigning them distinct table numbers, and renumber all the uses as
 // appropriate.  At the same time, the linker has special logic to build the
 // indirect function table if it is needed.
@@ -277,7 +278,7 @@ void ObjFile::addLegacyIndirectFunctionTableIfNeeded(
     return;
 
   // It's possible for an input to define tables and also use the indirect
-  // function table, but forget to compile with -mattr=+reference-types.
+  // function table, but forget to compile with -mattr=+call-indirect-overlong.
   // For these newer files, we require symbols for all tables, and
   // relocations for all of their uses.
   if (tableSymbolCount != 0) {