[lld] Teach LLD how to parse most linker scripts

This patch does *not* implement any semantic actions, but it is a first step to
teach LLD how to read complete linker scripts. The additional linker scripts
statements whose parsing is now supported are:

* SEARCH_DIR directive
* SECTIONS directive
* Symbol definitions inside SECTIONS including PROVIDE and PROVIDE_HIDDEN
* C-like expressions used in many places in linker scripts
* Input to output sections mapping

The goal of this commit was guided towards completely parsing a default GNU ld
linker script and the linker script used to link the FreeBSD kernel. Thus, it
also adds a test case based on the default linker script used in GNU ld for
x86_64 ELF targets. I tested SPEC userland programs linked by GNU ld, using the
linker script dump'ed by this parser, and everything went fine. I then tested
linking the FreeBSD kernel with a dump'ed linker script, installed the new
kernel and booted it, everything went fine.

Directives that still need to be implemented:
* MEMORY
* PHDRS

Reviewers: silvas, shankarke and ruiu

http://reviews.llvm.org/D5852

llvm-svn: 221126

1 files changed, 25 insertions, 0 deletions

diff --git a/lld/test/LinkerScript/missing-output-section-name.test b/lld/test/LinkerScript/missing-output-section-name.test
new file mode 100644
index 00000000000..79792982b61
--- /dev/null
+++ b/lld/test/LinkerScript/missing-output-section-name.test
@@ -0,0 +1,25 @@
+/*
+  RUN: linker-script-test %s 2> %t | FileCheck %s
+  RUN: FileCheck -input-file %t -check-prefix=CHECK-ERR %s
+*/
+SECTIONS {
+    : { *()}
+/*
+CHECK-ERR: [[@LINE-2]]:5: error: expected symbol assignment, entry, overlay or output section name
+CHECK-ERR-NEXT: {{^    : { \*\(\)}}}
+CHECK-ERR-NEXT: {{^    \^}}
+*/
+}
+
+/*
+CHECK: kw_sections: SECTIONS
+CHECK: l_brace: {
+CHECK: colon: :
+CHECK: l_brace: {
+CHECK: star: *
+CHECK: l_paren: (
+CHECK: r_paren: )
+CHECK: r_brace: }
+CHECK: r_brace: }
+CHECK: eof:
+*/