[lld] e29ee27 - [lld][WebAssembly] Allow `--no-stack-first` in addition to `--stack-first` (#166384)

[via llvm-commits]

Author: Sam Clegg
Date: 2025-11-04T18:40:46Z
New Revision: e29ee270615f3c8e3c9a0a657c0be43f9d76f441

URL: https://github.com/llvm/llvm-project/commit/e29ee270615f3c8e3c9a0a657c0be43f9d76f441
DIFF: https://github.com/llvm/llvm-project/commit/e29ee270615f3c8e3c9a0a657c0be43f9d76f441.diff

LOG: [lld][WebAssembly] Allow `--no-stack-first` in addition to `--stack-first` (#166384)

This paves the way to make `--stack-first` the default.

See: #151015

Added: 
    

Modified: 
    lld/test/wasm/stack-first.test
    lld/wasm/Driver.cpp
    lld/wasm/Options.td

Removed: 
    


################################################################################
diff  --git a/lld/test/wasm/stack-first.test b/lld/test/wasm/stack-first.test
index 72e1a006d5700..46e8c6ebc2381 100644
--- a/lld/test/wasm/stack-first.test
+++ b/lld/test/wasm/stack-first.test
@@ -8,6 +8,15 @@ RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/stack-first.
 RUN: wasm-ld -z stack-size=512 --stack-first --export=__data_end --export=__heap_base --export=someByte -o %t.wasm %t.o
 RUN: obj2yaml %t.wasm | FileCheck %s
 
+; Check `--no-stack-first`
+RUN: wasm-ld -z stack-size=512 --stack-first --no-stack-first --export=__data_end --export=__heap_base --export=someByte -o %t.wasm %t.o
+RUN: obj2yaml %t.wasm | FileCheck %s --check-prefix=NOT-FIRST
+
+; Check that the default is no-stack-first
+RUN: wasm-ld -z stack-size=512 --export=__data_end --export=__heap_base --export=someByte -o %t.wasm %t.o
+RUN: obj2yaml %t.wasm | FileCheck %s --check-prefix=NOT-FIRST
+
+
 CHECK:        - Type:            GLOBAL
 CHECK-NEXT:     Globals:         
 CHECK-NEXT:       - Index:           0
@@ -51,3 +60,19 @@ CHECK-NEXT:         Index:           2
 CHECK-NEXT:       - Name:            __heap_base
 CHECK-NEXT:         Kind:            GLOBAL
 CHECK-NEXT:         Index:           3
+
+NOT-FIRST:        - Type:            GLOBAL
+NOT-FIRST-NEXT:     Globals:
+NOT-FIRST-NEXT:       - Index:           0
+NOT-FIRST-NEXT:         Type:            I32
+NOT-FIRST-NEXT:         Mutable:         true
+NOT-FIRST-NEXT:         InitExpr:
+NOT-FIRST-NEXT:           Opcode:          I32_CONST
+NOT-FIRST-NEXT:           Value:           1552
+NOT-FIRST-NEXT:       - Index:           1
+NOT-FIRST-NEXT:         Type:            I32
+NOT-FIRST-NEXT:         Mutable:         false
+NOT-FIRST-NEXT:         InitExpr:
+NOT-FIRST-NEXT:           Opcode:          I32_CONST
+NOT-FIRST-NEXT:           Value:           1024
+

diff  --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
index 9c0e1b58e62f9..aad8095881bba 100644
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -595,7 +595,7 @@ static void readConfigs(opt::InputArgList &args) {
   ctx.arg.shlibSigCheck = !args.hasArg(OPT_no_shlib_sigcheck);
   ctx.arg.stripAll = args.hasArg(OPT_strip_all);
   ctx.arg.stripDebug = args.hasArg(OPT_strip_debug);
-  ctx.arg.stackFirst = args.hasArg(OPT_stack_first);
+  ctx.arg.stackFirst = args.hasFlag(OPT_stack_first, OPT_no_stack_first, false);
   ctx.arg.trace = args.hasArg(OPT_trace);
   ctx.arg.thinLTOCacheDir = args.getLastArgValue(OPT_thinlto_cache_dir);
   ctx.arg.thinLTOCachePolicy = CHECK(

diff  --git a/lld/wasm/Options.td b/lld/wasm/Options.td
index 2f699e2f68350..0ed69258d99aa 100644
--- a/lld/wasm/Options.td
+++ b/lld/wasm/Options.td
@@ -250,8 +250,9 @@ def no_entry: FF<"no-entry">,
 def no_shlib_sigcheck: FF<"no-shlib-sigcheck">,
   HelpText<"Do not check signatures of functions defined in shared libraries.">;
 
-def stack_first: FF<"stack-first">,
-  HelpText<"Place stack at start of linear memory rather than after data">;
+defm stack_first: B<"stack-first",
+    "Place stack at start of linear memory",
+    "Place the stack after static data refion (default)">;
 
 def table_base: JJ<"table-base=">,
   HelpText<"Table offset at which to place address taken functions (Defaults to 1)">;