Auto merge of #44440 - cuviper:min_global_align, r=japaric

Add `TargetOptions::min_global_align`, with s390x at 16-bit

The SystemZ `LALR` instruction provides PC-relative addressing for globals,
but only to *even* addresses, so other compilers make sure that such
globals are always 2-byte aligned.  In Clang, this is modeled with
`TargetInfo::MinGlobalAlign`, and `TargetOptions::min_global_align` now
serves the same purpose for rustc.

In Clang, the only targets that set this are SystemZ, Lanai, and NVPTX, and
the latter two don't have targets in rust master.

Fixes #44411.
r? @eddyb

2 files changed, 60 insertions, 0 deletions

diff --git a/src/test/run-make/min-global-align/Makefile b/src/test/run-make/min-global-align/Makefile
new file mode 100644
index 00000000000..2eacc36f380
--- /dev/null
+++ b/src/test/run-make/min-global-align/Makefile
@@ -0,0 +1,22 @@
+-include ../tools.mk
+
+# This tests ensure that global variables respect the target minimum alignment.
+# The three bools `STATIC_BOOL`, `STATIC_MUT_BOOL`, and `CONST_BOOL` all have
+# type-alignment of 1, but some targets require greater global alignment.
+
+SRC = min_global_align.rs
+LL = $(TMPDIR)/min_global_align.ll
+
+all:
+ifeq ($(UNAME),Linux)
+# Most targets are happy with default alignment -- take i686 for example.
+ifeq ($(filter x86,$(LLVM_COMPONENTS)),x86)
+	$(RUSTC) --target=i686-unknown-linux-gnu --emit=llvm-ir $(SRC)
+	[ "$$(grep -c 'align 1' "$(LL)")" -eq "3" ]
+endif
+# SystemZ requires even alignment for PC-relative addressing.
+ifeq ($(filter systemz,$(LLVM_COMPONENTS)),systemz)
+	$(RUSTC) --target=s390x-unknown-linux-gnu --emit=llvm-ir $(SRC)
+	[ "$$(grep -c 'align 2' "$(LL)")" -eq "3" ]
+endif
+endif
diff --git a/src/test/run-make/min-global-align/min_global_align.rs b/src/test/run-make/min-global-align/min_global_align.rs
new file mode 100644
index 00000000000..3d4f9001a74
--- /dev/null
+++ b/src/test/run-make/min-global-align/min_global_align.rs
@@ -0,0 +1,38 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(no_core, lang_items)]
+#![crate_type="rlib"]
+#![no_core]
+
+pub static STATIC_BOOL: bool = true;
+
+pub static mut STATIC_MUT_BOOL: bool = true;
+
+const CONST_BOOL: bool = true;
+pub static CONST_BOOL_REF: &'static bool = &CONST_BOOL;
+
+
+#[lang = "sized"]
+trait Sized {}
+
+#[lang = "copy"]
+trait Copy {}
+
+#[lang = "freeze"]
+trait Freeze {}
+
+#[lang = "sync"]
+trait Sync {}
+impl Sync for bool {}
+impl Sync for &'static bool {}
+
+#[lang="drop_in_place"]
+pub unsafe fn drop_in_place<T: ?Sized>(_: *mut T) { }