[lld] Make ALIGN work with -r in linker scripts

[kettenis]

Summary

Make ALIGN work in linker scripts used with the -r option. This works in GNU ld (ld.bfd) and is used to generate the "random gap" object for linking the OpenBSD kernel.

[ruiu]

LGTM

[jhenderson]

test/ELF/linkerscript/align.s

45 ↗

(On Diff #146641)

Nit: modificator -> modifier or expression

[grimar]

test/ELF/linkerscript/align.s

51 ↗

(On Diff #146641)

This script has no differences from the script right above on lines 35-41.
Hence you do not need it. And actually, you do not use it.

[kettenis]

test/ELF/linkerscript/align.s

45 ↗

(On Diff #146641)

What can I say; just copy and pasted it from the existing example. Want me to cange that one too?

51 ↗

(On Diff #146641)

Right. I'll remove that one and change the command slightly such that it doesn't overwrite the output of the previous test.

[jhenderson]

test/ELF/linkerscript/align.s

45 ↗

(On Diff #146641)

Yes, please. "Modificator" isn't a word.

[kettenis]

New diff that fixes the regression test.

[grimar]

LGTM

[kettenis]

Would one of you be so kind to commit this for me?

lld/trunk/ELF/LinkerScript.cpp

void LinkerScript::adjustSectionsBeforeSorting() {
   // the previous sections. Only a few flags are needed to keep the impact low.
   uint64_t Flags = SHF_ALLOC;
 
   for (BaseCommand *&Cmd : SectionCommands) {
     auto *Sec = dyn_cast<OutputSection>(Cmd);
     if (!Sec)
       continue;
 
+    // Handle align (e.g. ".foo : ALIGN(16) { ... }").
+    if (Sec->AlignExpr)
+      Sec->Alignment =
+          std::max<uint32_t>(Sec->Alignment, Sec->AlignExpr().getValue());
+
     // A live output section means that some input section was added to it. It
     // might have been removed (if it was empty synthetic section), but we at
     // least know the flags.
     if (Sec->Live)
       Flags = Sec->Flags;
 
     // We do not want to keep any special flags for output section
     // in case it is empty.
for (BaseCommand *Base : SectionCommands) {
     if (auto *Sec = dyn_cast<OutputSection>(Base)) {
       if (!Sec->LMARegionName.empty()) {
         if (MemoryRegion *M = MemoryRegions.lookup(Sec->LMARegionName))
           Sec->LMARegion = M;
         else
           error("memory region '" + Sec->LMARegionName + "' not declared");
       }
       Sec->MemRegion = findMemoryRegion(Sec);
-      // Handle align (e.g. ".foo : ALIGN(16) { ... }").
-      if (Sec->AlignExpr)
-        Sec->Alignment =
-            std::max<uint32_t>(Sec->Alignment, Sec->AlignExpr().getValue());
     }
   }
 
   // If output section command doesn't specify any segments,
   // and we haven't previously assigned any section to segment,
   // then we simply assign section to the very first load segment.
   // Below is an example of such linker script:
   // PHDRS { seg PT_LOAD; }

lld/trunk/test/ELF/linkerscript/align-r.test

+# REQUIRES: x86
+
+## Check output section ALIGN modifier with -r
+
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %p/Inputs/align.s -o %t1.o
+# RUN: ld.lld -r -o %t2.o --script %s %t1.o
+# RUN: llvm-readelf -s %t2.o | FileCheck %s
+
+# CHECK:      Section Headers:
+# CHECK-NEXT: Name Type     Address          Off    Size   ES Flg Lk Inf Al
+# CHECK-NEXT:      NULL     0000000000000000 000000 000000 00
+# CHECK-NEXT: .aaa PROGBITS 0000000000000000 000040 000008 00   A  0   0   1
+# CHECK-NEXT: .bbb PROGBITS 0000000000000000 001000 000008 00   A  0   0  4096
+# CHECK-NEXT: .ccc PROGBITS 0000000000000000 004000 000008 00   A  0   0  16384
+
+SECTIONS {
+  . = 0x10000;
+  .aaa : { *(.aaa) }
+  .bbb : ALIGN(4096) { *(.bbb) }
+  .ccc : ALIGN(4096 * 4) { *(.ccc) }
+}