Rollup merge of #45094 - japaric:strict-align, r=alexcrichton

enable strict alignment (+strict-align) on ARMv6

As discovered in #44538 ARMv6 devices may or may not support unaligned memory accesses. ARMv6
Linux *seems* to have no problem with unaligned accesses but this is because the kernel is stepping
in to fix each unaligned memory access -- this incurs in a performance penalty.

This commit enforces aligned memory accesses on all our in-tree ARM targets that may be used with
ARMv6 devices. This should improve performance of Rust programs on ARMv6 devices. For the record,
clang also applies this attribute when targeting ARMv6 devices that are not running Darwin or
NetBSD.

closes #44538
r? @alexcrichton

5 files changed, 5 insertions, 5 deletions

diff --git a/src/librustc_back/target/arm_linux_androideabi.rs b/src/librustc_back/target/arm_linux_androideabi.rs
index e93a9a788a4..ba21b1df032 100644
--- a/src/librustc_back/target/arm_linux_androideabi.rs
+++ b/src/librustc_back/target/arm_linux_androideabi.rs
@@ -14,7 +14,7 @@ use target::{Target, TargetOptions, TargetResult};
 pub fn target() -> TargetResult {
     let mut base = super::android_base::opts();
     // https://developer.android.com/ndk/guides/abis.html#armeabi
-    base.features = "+v5te".to_string();
+    base.features = "+strict-align,+v5te".to_string();
     base.max_atomic_width = Some(64);
 
     Ok(Target {
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
index b9f40accaeb..e630376a67d 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabi.rs
@@ -27,7 +27,7 @@ pub fn target() -> TargetResult {
         linker_flavor: LinkerFlavor::Gcc,
 
         options: TargetOptions {
-            features: "+v6".to_string(),
+            features: "+strict-align,+v6".to_string(),
             abi_blacklist: super::arm_base::abi_blacklist(),
             .. base
         },
diff --git a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
index a3ea69caec6..178a948b2b9 100644
--- a/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
+++ b/src/librustc_back/target/arm_unknown_linux_gnueabihf.rs
@@ -27,7 +27,7 @@ pub fn target() -> TargetResult {
         linker_flavor: LinkerFlavor::Gcc,
 
         options: TargetOptions {
-            features: "+v6,+vfp2".to_string(),
+            features: "+strict-align,+v6,+vfp2".to_string(),
             abi_blacklist: super::arm_base::abi_blacklist(),
             .. base
         }
diff --git a/src/librustc_back/target/arm_unknown_linux_musleabi.rs b/src/librustc_back/target/arm_unknown_linux_musleabi.rs
index 598f722d9af..29720ec5efc 100644
--- a/src/librustc_back/target/arm_unknown_linux_musleabi.rs
+++ b/src/librustc_back/target/arm_unknown_linux_musleabi.rs
@@ -16,7 +16,7 @@ pub fn target() -> TargetResult {
 
     // Most of these settings are copied from the arm_unknown_linux_gnueabi
     // target.
-    base.features = "+v6".to_string();
+    base.features = "+strict-align,+v6".to_string();
     base.max_atomic_width = Some(64);
     Ok(Target {
         // It's important we use "gnueabi" and not "musleabi" here. LLVM uses it
diff --git a/src/librustc_back/target/arm_unknown_linux_musleabihf.rs b/src/librustc_back/target/arm_unknown_linux_musleabihf.rs
index ea0bf75b103..fc8313877f6 100644
--- a/src/librustc_back/target/arm_unknown_linux_musleabihf.rs
+++ b/src/librustc_back/target/arm_unknown_linux_musleabihf.rs
@@ -16,7 +16,7 @@ pub fn target() -> TargetResult {
 
     // Most of these settings are copied from the arm_unknown_linux_gnueabihf
     // target.
-    base.features = "+v6,+vfp2".to_string();
+    base.features = "+strict-align,+v6,+vfp2".to_string();
     base.max_atomic_width = Some(64);
     Ok(Target {
         // It's important we use "gnueabihf" and not "musleabihf" here. LLVM