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From 93adcb770b99351b18553089c164fe3ef2119699 Mon Sep 17 00:00:00 2001
From: Sam Clegg <sbc@chromium.org>
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)
|