Allow /STACK in #pragma comment(linker, ...)

[alexreinking]

Summary

The Halide project uses #pragma comment(linker, "/STACK:...") to set the stack size high enough for our embedded compiler to run in end-user programs on Windows.

Unfortunately, lld-link.exe breaks on this when embedded in a COFF object, despite supporting the flag on the command line. MSVC's link.exe supports this fine. This patch extends support for this to lld-link.exe for better compatibility with MSVC projects.

[alexreinking]

Fix formatting.

[mstorsjo]

This looks sensible to me (especially assuming that link.exe allows /stack options in directives - I didn't verify this myself). It will need a testcase added before it can be landed though.

[rnk]

I verified MSVC supports this. This does need a test, and one can be made by combining the techniques in the lld/test/COFF/stack.test test and the directives.s test.

[thakis]

(marking this "Request Changes" for the missing test)

[rnk]

I found a spare moment to add the test and went ahead and pushed this. Thanks!

[alexreinking]

No, thank you, @rnk, for adding the test! I've been busy with my grad school obligations lately and this wound up pretty far down my to-do list. I'm happy this could get merged 🙂

lld/COFF/Driver.cpp

case OPT_merge:
       parseMerge(arg->getValue());
       break;
     case OPT_nodefaultlib:
       config->noDefaultLibs.insert(doFindLib(arg->getValue()).lower());
       break;
     case OPT_section:
       parseSection(arg->getValue());
       break;
+    case OPT_stack:
+      parseNumbers(arg->getValue(), &config->stackReserve,
+                   &config->stackCommit);
+      break;
     case OPT_subsystem: {
       bool gotVersion = false;
       parseSubsystem(arg->getValue(), &config->subsystem,
                      &config->majorSubsystemVersion,
                      &config->minorSubsystemVersion, &gotVersion);
       if (gotVersion) {
         config->majorOSVersion = config->majorSubsystemVersion;
         config->minorOSVersion = config->minorSubsystemVersion;

lld/test/COFF/stack-drectve.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-win32 %s -o %t.obj
+# RUN: lld-link /out:%t.exe /entry:main %t.obj
+# RUN: llvm-readobj --file-headers %t.exe | FileCheck %s
+
+# CHECK: SizeOfStackReserve: 20480
+# CHECK: SizeOfStackCommit: 12288
+
+  .text
+  .globl main
+main:
+  mov $42, %eax
+  ret
+
+  .section  .drectve,"yn"
+  .ascii  " -stack:0x5000,0x3000"