[LLD] Add memory ORIGIN and LENGTH expression support

[raidiun]

Summary

Adds support for the ORIGIN and LENGTH linker script built in functions.
ORIGIN(memory) Return the origin of the memory region
LENGTH(memory) Return the length of the memory region

Redo of D29775 for refactored linker script parsing

[ruiu]

LGTM

[raidiun]

I don't have commit access. Can someone get this for me? Thanks.

lld/trunk/ELF/ScriptParser.cpp

if (Tok == "DATA_SEGMENT_RELRO_END") {
     readExpr();
     expect(")");
     return [] { return alignTo(Script->getDot(), Target->PageSize); };
   }
   if (Tok == "DEFINED") {
     StringRef Name = readParenLiteral();
     return [=] { return Script->isDefined(Name) ? 1 : 0; };
   }
+  if (Tok == "LENGTH") {
+    StringRef Name = readParenLiteral();
+    if (Script->Opt.MemoryRegions.count(Name) == 0)
+      setError("memory region not defined: " + Name);
+    return [=] { return Script->Opt.MemoryRegions[Name].Length; };
+  }
   if (Tok == "LOADADDR") {
     StringRef Name = readParenLiteral();
     return [=] { return Script->getOutputSection(Location, Name)->getLMA(); };
   }
+  if (Tok == "ORIGIN") {
+    StringRef Name = readParenLiteral();
+    if (Script->Opt.MemoryRegions.count(Name) == 0)
+      setError("memory region not defined: " + Name);
+    return [=] { return Script->Opt.MemoryRegions[Name].Origin; };
+  }
   if (Tok == "SEGMENT_START") {
     expect("(");
     skip();
     expect(",");
     Expr E = readExpr();
     expect(")");
     return [=] { return E(); };
   }

lld/trunk/test/ELF/linkerscript/symbol-memoryexpr.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+
+# RUN: echo "MEMORY { \
+# RUN:   ram (rwx)  : ORIGIN = 0x8000, LENGTH = 256K \
+# RUN: } \
+# RUN: SECTIONS { \
+# RUN:         origin = ORIGIN(ram); \
+# RUN:         length = LENGTH(ram); \
+# RUN:         end    = ORIGIN(ram) + LENGTH(ram); \
+# RUN:       }" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -t %t1 | FileCheck %s
+
+# CHECK:      SYMBOL TABLE:
+# CHECK-NEXT: 0000000000000000 *UND* 00000000
+# CHECK-NEXT: 0000000000008000 .text 00000000 _start
+# CHECK-NEXT: 0000000000008000 *ABS* 00000000 origin
+# CHECK-NEXT: 0000000000040000 *ABS* 00000000 length
+# CHECK-NEXT: 0000000000048000 *ABS* 00000000 end
+
+# RUN: echo "SECTIONS { \
+# RUN:         no_exist_origin = ORIGIN(ram); \
+# RUN:         no_exist_length = LENGTH(ram); \
+# RUN:       }" > %t2.script
+# RUN: not ld.lld -o %t2 --script %t2.script %t 2>&1 \
+# RUN:  | FileCheck -check-prefix=ERR %s
+# ERR: {{.*}}.script:1: memory region not defined: ram
+
+
+.global _start
+_start:
+ nop