Auto merge of #27076 - alexcrichton:update-llvm, r=brson

LLVM has recently created their 3.7 release branch, and this PR updates us to that point. This should hopefully mean that we're basically compatible with the upcoming 3.7 release. Additionally, there are a number of goodies on this branch.

* This contains a fix for https://llvm.org/bugs/show_bug.cgi?id=23957
  which should help us bootstrap farther on 32-bit MSVC targets.
* There is better support for writing multiple flavors of archives, allowing us
  to use the built-in LLVM support instead of the system `ar` on all current
  platforms of the compiler.
* This LLVM has SafeStack support
* An [optimization patch](rust-lang/llvm@7cf5e26) by @pcwalton is included.
* A number of other minor test fixes here and there.

Due to problems dealing with the data layout we pass to LLVM, this PR also takes the time to clean up how we specific this. We no longer specify a data layout to LLVM by default and instead take the default for the target from LLVM to pass to the module that we're building. This should be more robust going into the future, and I'm also not sure we know what any of these arcane strings are any more...

Author: bors

src/librustc/lib.rs

@@ -99,14 +99,8 @@ pub mod diagnostics;
 
 pub mod back {
     pub use rustc_back::abi;
-    pub use rustc_back::arm;
-    pub use rustc_back::mips;
-    pub use rustc_back::mipsel;
     pub use rustc_back::rpath;
     pub use rustc_back::svh;
-    pub use rustc_back::target_strs;
-    pub use rustc_back::x86;
-    pub use rustc_back::x86_64;
 }
 
 pub mod ast_map;

src/librustc_back/arm.rs

@@ -52,13 +52,7 @@ extern crate rustc_llvm;
 
 pub mod abi;
 pub mod tempdir;
-pub mod arm;
-pub mod mips;
-pub mod mipsel;
 pub mod rpath;
 pub mod sha2;
 pub mod svh;
-pub mod target_strs;
-pub mod x86;
-pub mod x86_64;
 pub mod target;

src/librustc_back/lib.rs

@@ -13,10 +13,6 @@ use super::apple_ios_base::{opts, Arch};
 
 pub fn target() -> Target {
     Target {
-        // reference layout: e-m:o-i64:64-i128:128-n32:64-S128
-        data_layout: "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
-                      i128:128-f32:32:32-f64:64:64-v64:64:64-v128:128:128-\
-                      a:0:64-n32:64-S128".to_string(),
         llvm_target: "arm64-apple-ios".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),

src/librustc_back/mips.rs

@@ -12,9 +12,6 @@ use target::Target;
 
 pub fn target() -> Target {
     Target {
-        data_layout: "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
-                      f32:32:32-f64:64:64-v64:64:64-v128:128:128-a:0:64-\
-                      n32:64-S128".to_string(),
         llvm_target: "aarch64-linux-android".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),

src/librustc_back/mipsel.rs

@@ -13,9 +13,6 @@ use target::Target;
 pub fn target() -> Target {
     let base = super::linux_base::opts();
     Target {
-        data_layout: "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
-                      f32:32:32-f64:64:64-v64:64:64-v128:128:128-a:0:64-\
-                      n32:64-S128".to_string(),
         llvm_target: "aarch64-unknown-linux-gnu".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "64".to_string(),

src/librustc_back/target/aarch64_apple_ios.rs

@@ -23,6 +23,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         dll_prefix: "lib".to_string(),
         dll_suffix: ".dylib".to_string(),
+        archive_format: "bsd".to_string(),
         pre_link_args: Vec::new(),
         .. Default::default()
     }

src/librustc_back/target/aarch64_linux_android.rs

@@ -15,9 +15,6 @@ pub fn target() -> Target {
     base.features = "+v7".to_string();
 
     Target {
-        data_layout: "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-\
-                      f32:32:32-f64:64:64-v64:64:64-v128:64:128-a:0:64-\
-                      n32".to_string(),
         llvm_target: "arm-linux-androideabi".to_string(),
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),