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[WebAssembly] Write initial memory in pages not bytes

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Subscribers: jfb, dschuff

Differential Revision: https://reviews.llvm.org/D32660

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301687 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sam Clegg 2017-04-28 21:12:09 +00:00
parent 8c9ed246f2
commit 649003c411
5 changed files with 29 additions and 3 deletions
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2
include/llvm/Support/Wasm.h
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@ -24,6 +24,8 @@ namespace wasm {
const char WasmMagic[] = {'\0', 'a', 's', 'm'};
// Wasm binary format version
const uint32_t WasmVersion = 0x1;
// Wasm uses a 64k page size
const uint32_t WasmPageSize = 65536;
struct WasmObjectHeader {
StringRef Magic;

6
lib/MC/WasmObjectWriter.cpp
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@ -913,12 +913,14 @@ void WasmObjectWriter::writeObject(MCAssembler &Asm,
// For now, always emit the memory section, since loads and stores are not
// valid without it. In the future, we could perhaps be more clever and omit
// it if there are no loads or stores.
startSection(Section, wasm::WASM_SEC_MEMORY);
uint32_t NumPages =
(DataBytes.size() + wasm::WasmPageSize - 1) / wasm::WasmPageSize;
startSection(Section, wasm::WASM_SEC_MEMORY);
encodeULEB128(1, getStream()); // number of memory spaces
encodeULEB128(0, getStream()); // flags
encodeULEB128(DataBytes.size(), getStream()); // initial
encodeULEB128(NumPages, getStream()); // initial
endSection(Section);

5
test/MC/WebAssembly/sections.ll
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@ -32,6 +32,11 @@ entry:
; CHECK: }
; CHECK: Section {
; CHECK: Type: MEMORY (0x5)
; CHECK: Memories [
; CHECK: Memory {
; CHECK: InitialPages: 1
; CHECK: }
; CHECK: ]
; CHECK: }
; CHECK: Section {
; CHECK: Type: GLOBAL (0x6)

5
test/tools/llvm-readobj/sections.test
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@ -518,6 +518,11 @@ WASM-NEXT: Section {
WASM-NEXT: Type: MEMORY (0x5)
WASM-NEXT: Size: 3
WASM-NEXT: Offset: 66
WASM-NEXT: Memories [
WASM-NEXT: Memory {
WASM-NEXT: InitialPages: 0
WASM-NEXT: }
WASM-NEXT: ]
WASM-NEXT: }
WASM-NEXT: Section {
WASM-NEXT: Type: EXPORT (0x7)

14
tools/llvm-readobj/WasmDumper.cpp
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@ -150,8 +150,20 @@ void WasmDumper::printSections() {
W.printEnum("Type", WasmSec.Type, makeArrayRef(WasmSectionTypes));
W.printNumber("Size", (uint64_t)WasmSec.Content.size());
W.printNumber("Offset", WasmSec.Offset);
if (WasmSec.Type == wasm::WASM_SEC_CUSTOM) {
switch (WasmSec.Type) {
case wasm::WASM_SEC_CUSTOM:
W.printString("Name", WasmSec.Name);
break;
case wasm::WASM_SEC_MEMORY:
ListScope Group(W, "Memories");
for (const wasm::WasmLimits &Memory : Obj->memories()) {
DictScope Group(W, "Memory");
W.printNumber("InitialPages", Memory.Initial);
if (Memory.Flags & wasm::WASM_LIMITS_FLAG_HAS_MAX) {
W.printNumber("MaxPages", WasmSec.Offset);
}
}
break;
}
if (opts::SectionRelocations) {