From 93adcb770b99351b18553089c164fe3ef2119699 Mon Sep 17 00:00:00 2001 From: Sam Clegg Date: Fri, 25 Aug 2023 13:56:16 -0700 Subject: [PATCH] [lld][WebAssembly] Add `--table-base` setting This is similar to `--global-base` but determines where to place the table segments rather than that data segments. See https://github.com/emscripten-core/emscripten/issues/20097 Differential Revision: https://reviews.llvm.org/D158892 --- test/wasm/table-base.s | 72 ++++++++++++++++++++++++++++++++++++++ wasm/Driver.cpp | 19 ++++++++-- wasm/Options.td | 5 ++- wasm/Writer.cpp | 8 ----- 4 files changed, 93 insertions(+), 11 deletions(-) create mode 100644 test/wasm/table-base.s diff --git a/test/wasm/table-base.s b/test/wasm/table-base.s new file mode 100644 index 000000000000000..56fff414fd31d96 --- /dev/null +++ b/test/wasm/table-base.s @@ -0,0 +1,72 @@ +# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %s -o %t.o + +# RUN: wasm-ld --export=__table_base -o %t.wasm %t.o +# RUN: obj2yaml %t.wasm | FileCheck %s -check-prefix=CHECK-DEFAULT + +# RUN: wasm-ld --table-base=100 --export=__table_base -o %t.wasm %t.o +# RUN: obj2yaml %t.wasm | FileCheck %s -check-prefix=CHECK-100 + +.globl _start +_start: + .functype _start () -> () + i32.const _start + drop + end_function + +# CHECK-DEFAULT: - Type: TABLE +# CHECK-DEFAULT-NEXT: Tables: +# CHECK-DEFAULT-NEXT: - Index: 0 +# CHECK-DEFAULT-NEXT: ElemType: FUNCREF +# CHECK-DEFAULT-NEXT: Limits: +# CHECK-DEFAULT-NEXT: Flags: [ HAS_MAX ] +# CHECK-DEFAULT-NEXT: Minimum: 0x2 +# CHECK-DEFAULT-NEXT: Maximum: 0x2 + +# CHECK-DEFAULT: - Type: GLOBAL +# CHECK-DEFAULT-NEXT: Globals: +# CHECK-DEFAULT-NEXT: - Index: 0 +# CHECK-DEFAULT-NEXT: Type: I32 +# CHECK-DEFAULT-NEXT: Mutable: true +# CHECK-DEFAULT-NEXT: InitExpr: +# CHECK-DEFAULT-NEXT: Opcode: I32_CONST +# CHECK-DEFAULT-NEXT: Value: 66560 +# CHECK-DEFAULT-NEXT: - Index: 1 +# CHECK-DEFAULT-NEXT: Type: I32 +# CHECK-DEFAULT-NEXT: Mutable: false +# CHECK-DEFAULT-NEXT: InitExpr: +# CHECK-DEFAULT-NEXT: Opcode: I32_CONST +# CHECK-DEFAULT-NEXT: Value: 1 + +# CHECK-DEFAULT: - Type: EXPORT +# CHECK-DEFAULT: - Name: __table_base +# CHECK-DEFAULT-NEXT: Kind: GLOBAL +# CHECK-DEFAULT-NEXT: Index: 1 + +# CHECK-100: - Type: TABLE +# CHECK-100-NEXT: Tables: +# CHECK-100-NEXT: - Index: 0 +# CHECK-100-NEXT: ElemType: FUNCREF +# CHECK-100-NEXT: Limits: +# CHECK-100-NEXT: Flags: [ HAS_MAX ] +# CHECK-100-NEXT: Minimum: 0x65 +# CHECK-100-NEXT: Maximum: 0x65 + +# CHECK-100: - Type: GLOBAL +# CHECK-100-NEXT: Globals: +# CHECK-100-NEXT: - Index: 0 +# CHECK-100-NEXT: Type: I32 +# CHECK-100-NEXT: Mutable: true +# CHECK-100-NEXT: InitExpr: +# CHECK-100-NEXT: Opcode: I32_CONST +# CHECK-100-NEXT: Value: 66560 +# CHECK-100-NEXT: - Index: 1 +# CHECK-100-NEXT: Type: I32 +# CHECK-100-NEXT: Mutable: false +# CHECK-100-NEXT: InitExpr: +# CHECK-100-NEXT: Opcode: I32_CONST +# CHECK-100-NEXT: Value: 100 + +# CHECK-100: - Type: EXPORT +# CHECK-100: - Name: __table_base +# CHECK-100-NEXT: Kind: GLOBAL +# CHECK-100-NEXT: Index: 1 diff --git a/wasm/Driver.cpp b/wasm/Driver.cpp index 84304881f5ca34e..c2f5f0185781f36 100644 --- a/wasm/Driver.cpp +++ b/wasm/Driver.cpp @@ -502,6 +502,7 @@ static void readConfigs(opt::InputArgList &args) { config->initialMemory = args::getInteger(args, OPT_initial_memory, 0); config->globalBase = args::getInteger(args, OPT_global_base, 0); + config->tableBase = args::getInteger(args, OPT_table_base, 0); config->maxMemory = args::getInteger(args, OPT_max_memory, 0); config->zStackSize = args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize); @@ -573,6 +574,17 @@ static void setConfigs() { if (config->exportTable) error("-shared/-pie is incompatible with --export-table"); config->importTable = true; + } else { + // Default table base. Defaults to 1, reserving 0 for the NULL function + // pointer. + if (!config->tableBase) + config->tableBase = 1; + // The default offset for static/global data, for when --global-base is + // not specified on the command line. The precise value of 1024 is + // somewhat arbitrary, and pre-dates wasm-ld (Its the value that + // emscripten used prior to wasm-ld). + if (!config->globalBase && !config->relocatable && !config->stackFirst) + config->globalBase = 1024; } if (config->relocatable) { @@ -666,8 +678,11 @@ static void checkOptions(opt::InputArgList &args) { warn("-Bsymbolic is only meaningful when combined with -shared"); } - if (config->globalBase && config->isPic) { - error("--global-base may not be used with -shared/-pie"); + if (config->isPic) { + if (config->globalBase) + error("--global-base may not be used with -shared/-pie"); + if (config->tableBase) + error("--table-base may not be used with -shared/-pie"); } } diff --git a/wasm/Options.td b/wasm/Options.td index 50417d2928e0a34..bb764396bf4df14 100644 --- a/wasm/Options.td +++ b/wasm/Options.td @@ -191,7 +191,7 @@ def growable_table: FF<"growable-table">, HelpText<"Remove maximum size from function table, allowing table to grow">; def global_base: JJ<"global-base=">, - HelpText<"Where to start to place global data">; + HelpText<"Memory offset at which to place global data (Defaults to 1024)">; def import_memory: FF<"import-memory">, HelpText<"Import the module's memory from the default module of \"env\" with the name \"memory\".">; @@ -224,6 +224,9 @@ def no_entry: FF<"no-entry">, def stack_first: FF<"stack-first">, HelpText<"Place stack at start of linear memory rather than after data">; +def table_base: JJ<"table-base=">, + HelpText<"Table offset at which to place address taken functions (Defaults to 1)">; + defm whole_archive: B<"whole-archive", "Force load of all members in a static library", "Do not force load of all members in a static library (default)">; diff --git a/wasm/Writer.cpp b/wasm/Writer.cpp index f25d358dc5bae6f..0576bf2907e49c4 100644 --- a/wasm/Writer.cpp +++ b/wasm/Writer.cpp @@ -358,13 +358,6 @@ void Writer::layoutMemory() { memoryPtr = config->globalBase; } } else { - if (!config->globalBase && !config->relocatable && !config->isPic) { - // The default offset for static/global data, for when --global-base is - // not specified on the command line. The precise value of 1024 is - // somewhat arbitrary, and pre-dates wasm-ld (Its the value that - // emscripten used prior to wasm-ld). - config->globalBase = 1024; - } memoryPtr = config->globalBase; } @@ -1685,7 +1678,6 @@ void Writer::run() { // For PIC code the table base is assigned dynamically by the loader. // For non-PIC, we start at 1 so that accessing table index 0 always traps. if (!config->isPic) { - config->tableBase = 1; if (WasmSym::definedTableBase) WasmSym::definedTableBase->setVA(config->tableBase); if (WasmSym::definedTableBase32)