commit 2e1504091e2b6e949290b4792224c4b833acda99
author Thomas Lively <tlively@google.com> Tue Feb 19 22:56:19 2019 +0000
committer Thomas Lively <tlively@google.com> Tue Feb 19 22:56:19 2019 +0000
tree b579df67b6a3b560a5520fea45f235e069588e3b
parent 8eade092497e17ad1cfbb1a7c3d9156686b229cc

[WebAssembly] Update MC for bulk memory

Summary:
Rename MemoryIndex to InitFlags and implement logic for determining
data segment layout in ObjectYAML and MC. Also adds a "passive" flag
for the .section assembler directive although this cannot be assembled
yet because the assembler does not support data sections.

Reviewers: sbc100, aardappel, aheejin, dschuff

Subscribers: jgravelle-google, hiraditya, sunfish, rupprecht, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57938

llvm-svn: 354397

llvm/lib/MC/MCParser/WasmAsmParser.cpp

diff --git a/llvm/lib/MC/MCParser/WasmAsmParser.cpp b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
index 17d86aa..a8a48d1 100644
--- a/llvm/lib/MC/MCParser/WasmAsmParser.cpp
+++ b/llvm/lib/MC/MCParser/WasmAsmParser.cpp
@@ -81,13 +81,53 @@
     return false;
   }
 
+  bool parseSectionFlags(StringRef FlagStr, bool &Passive) {
+    SmallVector<StringRef, 2> Flags;
+    // If there are no flags, keep Flags empty
+    FlagStr.split(Flags, ",", -1, false);
+    for (auto &Flag : Flags) {
+      if (Flag == "passive")
+        Passive = true;
+      else
+        return error("Expected section flags, instead got: ", Lexer->getTok());
+    }
+    return false;
+  }
+
   bool parseSectionDirective(StringRef, SMLoc) {
     StringRef Name;
     if (Parser->parseIdentifier(Name))
       return TokError("expected identifier in directive");
-    // FIXME: currently requiring this very fixed format.
-    if (expect(AsmToken::Comma, ",") || expect(AsmToken::String, "string") ||
-        expect(AsmToken::Comma, ",") || expect(AsmToken::At, "@") ||
+
+    if (expect(AsmToken::Comma, ","))
+      return true;
+
+    if (Lexer->isNot(AsmToken::String))
+      return error("expected string in directive, instead got: ", Lexer->getTok());
+
+    SectionKind Kind = StringSwitch<SectionKind>(Name)
+                       .StartsWith(".data", SectionKind::getData())
+                       .StartsWith(".rodata", SectionKind::getReadOnly())
+                       .StartsWith(".text", SectionKind::getText())
+                       .StartsWith(".custom_section", SectionKind::getMetadata());
+
+    MCSectionWasm* Section = getContext().getWasmSection(Name, Kind);
+
+    // Update section flags if present in this .section directive
+    bool Passive = false;
+    if (parseSectionFlags(getTok().getStringContents(), Passive))
+      return true;
+
+    if (Passive) {
+      if (!Section->isWasmData())
+        return Parser->Error(getTok().getLoc(),
+                             "Only data sections can be passive");
+      Section->setPassive();
+    }
+
+    Lex();
+
+    if (expect(AsmToken::Comma, ",") || expect(AsmToken::At, "@") ||
         expect(AsmToken::EndOfStatement, "eol"))
       return true;
     // This is done automatically by the assembler for text sections currently,

llvm/lib/MC/MCSectionWasm.cpp

diff --git a/llvm/lib/MC/MCSectionWasm.cpp b/llvm/lib/MC/MCSectionWasm.cpp
index 164ded9..8633c10 100644
--- a/llvm/lib/MC/MCSectionWasm.cpp
+++ b/llvm/lib/MC/MCSectionWasm.cpp
@@ -62,7 +62,8 @@
   printName(OS, getSectionName());
   OS << ",\"";
 
-  // TODO: Print section flags.
+  if (IsPassive)
+    OS << "passive";
 
   OS << '"';
 

llvm/lib/MC/WasmObjectWriter.cpp

diff --git a/llvm/lib/MC/WasmObjectWriter.cpp b/llvm/lib/MC/WasmObjectWriter.cpp
index 600928c..10f16ba 100644
--- a/llvm/lib/MC/WasmObjectWriter.cpp
+++ b/llvm/lib/MC/WasmObjectWriter.cpp
@@ -106,9 +106,10 @@
 struct WasmDataSegment {
   MCSectionWasm *Section;
   StringRef Name;
+  uint32_t InitFlags;
   uint32_t Offset;
   uint32_t Alignment;
-  uint32_t Flags;
+  uint32_t LinkerFlags;
   SmallVector<char, 4> Data;
 };
 
@@ -899,10 +900,14 @@
   encodeULEB128(DataSegments.size(), W.OS); // count
 
   for (const WasmDataSegment &Segment : DataSegments) {
-    encodeULEB128(0, W.OS); // memory index
-    W.OS << char(wasm::WASM_OPCODE_I32_CONST);
-    encodeSLEB128(Segment.Offset, W.OS); // offset
-    W.OS << char(wasm::WASM_OPCODE_END);
+    encodeULEB128(Segment.InitFlags, W.OS); // flags
+    if (Segment.InitFlags & wasm::WASM_SEGMENT_HAS_MEMINDEX)
+      encodeULEB128(0, W.OS); // memory index
+    if ((Segment.InitFlags & wasm::WASM_SEGMENT_IS_PASSIVE) == 0) {
+      W.OS << char(wasm::WASM_OPCODE_I32_CONST);
+      encodeSLEB128(Segment.Offset, W.OS); // offset
+      W.OS << char(wasm::WASM_OPCODE_END);
+    }
     encodeULEB128(Segment.Data.size(), W.OS); // size
     Segment.Section->setSectionOffset(W.OS.tell() - Section.ContentsOffset);
     W.OS << Segment.Data; // data
@@ -1013,7 +1018,7 @@
     for (const WasmDataSegment &Segment : DataSegments) {
       writeString(Segment.Name);
       encodeULEB128(Segment.Alignment, W.OS);
-      encodeULEB128(Segment.Flags, W.OS);
+      encodeULEB128(Segment.LinkerFlags, W.OS);
     }
     endSection(SubSection);
   }
@@ -1253,11 +1258,12 @@
       DataSegments.emplace_back();
       WasmDataSegment &Segment = DataSegments.back();
       Segment.Name = SectionName;
+      Segment.InitFlags = Section.getPassive() ? wasm::WASM_SEGMENT_IS_PASSIVE : 0;
       Segment.Offset = DataSize;
       Segment.Section = &Section;
       addData(Segment.Data, Section);
       Segment.Alignment = Log2_32(Section.getAlignment());
-      Segment.Flags = 0;
+      Segment.LinkerFlags = 0;
       DataSize += Segment.Data.size();
       Section.setSegmentIndex(SegmentIndex);