[ELF] Use late evaluation for ALIGN in expression

While the following expression is handled fine:

  PROVIDE_HIDDEN(newsym = oldsym + address);

The following expression triggers an error because the expression
is evaluated as absolute:

  PROVIDE_HIDDEN(newsym = ALIGN(oldsym, CONSTANT(MAXPAGESIZE)) + address);

To avoid this error, we use late evaluation for ALIGN by making the
alignment an attribute of the expression itself.

Differential Revision: https://reviews.llvm.org/D33629

llvm-svn: 304185

lld/ELF/LinkerScript.cpp

@@ -52,11 +52,12 @@ LinkerScript *elf::Script;
 uint64_t ExprValue::getValue() const {
   if (Sec) {
     if (Sec->getOutputSection())
-      return Sec->getOffset(Val) + Sec->getOutputSection()->Addr;
+      return alignTo(Sec->getOffset(Val) + Sec->getOutputSection()->Addr,
+                     Alignment);
     error("unable to evaluate expression: input section " + Sec->Name +
           " has no output section assigned");
   }
-  return Val;
+  return alignTo(Val, Alignment);
 }
 
 uint64_t ExprValue::getSecAddr() const {
@@ -143,7 +144,7 @@ void LinkerScript::assignSymbol(SymbolAssignment *Cmd, bool InSec) {
   } else {
     Sym->Section = V.Sec;
     if (Sym->Section->Flags & SHF_ALLOC)
-      Sym->Value = V.Val;
+      Sym->Value = alignTo(V.Val, V.Alignment);
     else
       Sym->Value = V.getValue();
   }

lld/ELF/LinkerScript.h

@@ -41,7 +41,12 @@ struct ExprValue {
   SectionBase *Sec;
   uint64_t Val;
   bool ForceAbsolute;
+  uint64_t Alignment = 1;
 
+  ExprValue(SectionBase *Sec, bool ForceAbsolute, uint64_t Val,
+            uint64_t Alignment)
+      : Sec(Sec), Val(Val), ForceAbsolute(ForceAbsolute), Alignment(Alignment) {
+  }
   ExprValue(SectionBase *Sec, bool ForceAbsolute, uint64_t Val)
       : Sec(Sec), Val(Val), ForceAbsolute(ForceAbsolute) {}
   ExprValue(SectionBase *Sec, uint64_t Val) : ExprValue(Sec, false, Val) {}

lld/ELF/ScriptParser.cpp

@@ -859,7 +859,11 @@ Expr ScriptParser::readPrimary() {
     expect(",");
     Expr E2 = readExpr();
     expect(")");
-    return [=] { return alignTo(E().getValue(), E2().getValue()); };
+    return [=] {
+      ExprValue V = E();
+      V.Alignment = E2().getValue();
+      return V;
+    };
   }
   if (Tok == "ALIGNOF") {
     StringRef Name = readParenLiteral();

lld/test/ELF/linkerscript/align.s

@@ -64,7 +64,7 @@
 # SYMBOLS-NEXT: 0000000000010000         *ABS*           00000000 __code_base__
 # SYMBOLS-NEXT: 0000000000001000         *ABS*           00000000 VAR
 # SYMBOLS-NEXT: 0000000000011000         .bbb            00000000 __start_bbb
-# SYMBOLS-NEXT: 0000000000012000         *ABS*           00000000 __end_bbb
+# SYMBOLS-NEXT: 0000000000012000         .bbb            00000000 __end_bbb
 
 .global _start
 _start:

lld/test/ELF/linkerscript/symbol-reserved.s

@@ -11,6 +11,12 @@
 
 # SHARED: 0000000000000005 .dynsym 00000000 .hidden newsym
 
+# RUN: echo "PROVIDE_HIDDEN(newsym = ALIGN(__ehdr_start, CONSTANT(MAXPAGESIZE)) + 5);" > %t.script
+# RUN: ld.lld -o %t1 %t.script %t
+# RUN: llvm-objdump -t %t1 | FileCheck --check-prefix=ALIGNED %s
+
+# ALIGNED: 0000000000200005 .text 00000000 .hidden newsym
+
 .global _start
 _start:
   lea newsym(%rip),%rax