[lld][WebAssembly] Add an --initial-heap option

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=<value>
+
+  Initial size of the heap. Default: zero.
+
 .. option:: --initial-memory=<value>
 
-  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=<value>
 

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

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;

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);

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">;
 

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");