From 183c6c5d9ec892fcb7021991c579549b9e22ce3a Mon Sep 17 00:00:00 2001 From: SingleAccretion Date: Fri, 15 Dec 2023 14:59:48 +0300 Subject: [PATCH] Add an "--initial-heap" option to wasm-ld It is beneficial to preallocate a certain number of pages in the linear memory (i. e. use the "minimum" field of WASM memories) so that fewer "memory.grow"s are needed at startup. So far, the way to do that has been to pass the "--initial-memory" option to the linker. It works, but has the very significant downside of requiring the user to know the size of static data beforehand, as it must not exceed the number of bytes passed-in as "--initial-memory". The new "--initial-heap" option avoids this downside by simply appending the specified number of pages to static data (and stack), regardless of how large they already are. --- lld/docs/WebAssembly.rst | 6 +++++- lld/test/wasm/initial-heap.test | 27 +++++++++++++++++++++++++++ lld/wasm/Config.h | 1 + lld/wasm/Driver.cpp | 5 +++-- lld/wasm/Options.td | 3 +++ lld/wasm/Writer.cpp | 10 ++++++++++ 6 files changed, 49 insertions(+), 3 deletions(-) create mode 100644 lld/test/wasm/initial-heap.test diff --git a/lld/docs/WebAssembly.rst b/lld/docs/WebAssembly.rst index dad3177e2c7df..3f554de46d38a 100644 --- a/lld/docs/WebAssembly.rst +++ b/lld/docs/WebAssembly.rst @@ -123,9 +123,13 @@ WebAssembly-specific options: is not possible for undefined data symbols. Undefined data symbols will still be reported as normal (in accordance with ``--unresolved-symbols``). +.. option:: --initial-heap= + + Initial size of the heap. Default: zero. + .. option:: --initial-memory= - Initial size of the linear memory. Default: static data size. + Initial size of the linear memory. Default: the sum of stack, static data and heap sizes. .. option:: --max-memory= diff --git a/lld/test/wasm/initial-heap.test b/lld/test/wasm/initial-heap.test new file mode 100644 index 0000000000000..3e8bbd36535d3 --- /dev/null +++ b/lld/test/wasm/initial-heap.test @@ -0,0 +1,27 @@ +RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/start.s -o %t.o + +; The initial heap size will be added to the stack size +RUN: wasm-ld %t.o -o %t1.wasm --stack-first -z stack-size=65536 --initial-heap=131072 +RUN: obj2yaml %t1.wasm | FileCheck %s --check-prefixes=CHECK,CHECK-2P + +; Also test that we can parse and process a large size correctly +RUN: wasm-ld %t.o -o %t2.wasm --stack-first -z stack-size=65536 --initial-heap=4294901760 +RUN: obj2yaml %t2.wasm | FileCheck %s --check-prefixes=CHECK,CHECK-4G + +CHECK: - Type: MEMORY +CHECK-NEXT: Memories: +CHECK-2P-NEXT: Minimum: 0x3 +CHECK-4G-NEXT: Minimum: 0x10000 + +; Test various error cases. +RUN: not wasm-ld %t.o -o %t3.wasm --initial-heap=131073 2>&1 | FileCheck %s --check-prefix NOT-PAGE-MULTIPLE +RUN: not wasm-ld %t.o -o %t4.wasm --stack-first -z stack-size=65536 --initial-heap=4295032832 2>&1 | FileCheck %s --check-prefix TOO-LARGE-BY-ITSELF +RUN: not wasm-ld %t.o -o %t5.wasm --stack-first -z stack-size=131072 --initial-heap=4294901760 2>&1 | FileCheck %s --check-prefix TOO-LARGE-WITH-STACK +RUN: not wasm-ld %t.o -o %t6.wasm --stack-first -z stack-size=65536 --initial-heap=131072 --initial-memory=131072 2>&1 | FileCheck %s --check-prefix INITIAL-MEMORY-TOO-SMALL +RUN: not wasm-ld %t.o -o %t7.wasm --stack-first -z stack-size=65536 --initial-heap=131072 --max-memory=131072 2>&1 | FileCheck %s --check-prefix MAX-MEMORY-TOO-SMALL + +NOT-PAGE-MULTIPLE: initial heap must be 65536-byte aligned +TOO-LARGE-BY-ITSELF: initial heap too large, cannot be greater than 4294901760 +TOO-LARGE-WITH-STACK: initial heap too large, cannot be greater than 4294836224 +INITIAL-MEMORY-TOO-SMALL: initial memory too small, 196608 bytes needed +MAX-MEMORY-TOO-SMALL: maximum memory too small, 196608 bytes needed diff --git a/lld/wasm/Config.h b/lld/wasm/Config.h index d76d43852acff..104d470484014 100644 --- a/lld/wasm/Config.h +++ b/lld/wasm/Config.h @@ -68,6 +68,7 @@ struct Configuration { bool isStatic = false; bool trace; uint64_t globalBase; + uint64_t initialHeap; uint64_t initialMemory; uint64_t maxMemory; uint64_t zStackSize; diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp index c68fe33a14e29..a354260c60525 100644 --- a/lld/wasm/Driver.cpp +++ b/lld/wasm/Driver.cpp @@ -502,9 +502,10 @@ static void readConfigs(opt::InputArgList &args) { errorHandler().verbose = args.hasArg(OPT_verbose); LLVM_DEBUG(errorHandler().verbose = true); - 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->globalBase = args::getInteger(args, OPT_global_base, 0); + config->initialHeap = args::getInteger(args, OPT_initial_heap, 0); + config->initialMemory = args::getInteger(args, OPT_initial_memory, 0); config->maxMemory = args::getInteger(args, OPT_max_memory, 0); config->zStackSize = args::getZOptionValue(args, OPT_z, "stack-size", WasmPageSize); diff --git a/lld/wasm/Options.td b/lld/wasm/Options.td index 2df6196d5e8ce..95ebc202a4518 100644 --- a/lld/wasm/Options.td +++ b/lld/wasm/Options.td @@ -215,6 +215,9 @@ defm soname: Eq<"soname", "Set the module name in the generated name section">; def import_table: FF<"import-table">, HelpText<"Import function table from the environment">; +def initial_heap: JJ<"initial-heap=">, + HelpText<"Initial size of the heap">; + def initial_memory: JJ<"initial-memory=">, HelpText<"Initial size of the linear memory">; diff --git a/lld/wasm/Writer.cpp b/lld/wasm/Writer.cpp index 0576bf2907e49..805018c58dccb 100644 --- a/lld/wasm/Writer.cpp +++ b/lld/wasm/Writer.cpp @@ -439,6 +439,16 @@ void Writer::layoutMemory() { maxMemorySetting = 1ULL << 34; } + if (config->initialHeap != 0) { + if (config->initialHeap != alignTo(config->initialHeap, WasmPageSize)) + error("initial heap must be " + Twine(WasmPageSize) + "-byte aligned"); + uint64_t maxInitialHeap = maxMemorySetting - memoryPtr; + if (config->initialHeap > maxInitialHeap) + error("initial heap too large, cannot be greater than " + + Twine(maxInitialHeap)); + memoryPtr += config->initialHeap; + } + if (config->initialMemory != 0) { if (config->initialMemory != alignTo(config->initialMemory, WasmPageSize)) error("initial memory must be " + Twine(WasmPageSize) + "-byte aligned");