Auto merge of #62474 - nikic:update-llvm, r=<try>

[WIP] Update to LLVM 9

Main changes:

 * In preparation for opaque pointer types, the `byval` attribute now takes a type. As such, the argument type needs to be threaded through to the function/callsite attribute application logic.
 * On ARM the `+fp-only-sp` and `+d16` features have become `-fp64` and `-d32`. I've switched the target definitions to use the new names, but also added bidirectional emulation so either can be used on any LLVM version for backwards compatibility.
 * The datalayout can now specify function pointer alignment. In particular on ARM `Fi8` is specified, which means that function pointer alignment is independent of function alignment. I've added this to our datalayouts to match LLVM (which is something we check) and strip the fnptr alignment for older LLVM versions.
 * The fmul/fadd reductions now always respect the accumulator (including for unordered reductions), so we should pass the identity instead of undef.

Open issues:

 * https://reviews.llvm.org/D62106 causes linker errors with ld.bdf due to https://sourceware.org/bugzilla/show_bug.cgi?id=24784. To avoid this I've enabled `RelaxELFRelocations`, which results in a GOTPCRELX relocation for `__tls_get_addr` and avoids the issue. However, this is likely not acceptable because relax relocations are not supported by older linker versions. We may need an LLVM option to keep using PLT for `__tls_get_addr` despite `RtLibUseGOT`.

r? @ghost

src/librustc_codegen_llvm/abi.rs

@@ -34,17 +34,17 @@ trait ArgAttributeExt {
 impl ArgAttributeExt for ArgAttribute {
     fn for_each_kind<F>(&self, mut f: F) where F: FnMut(llvm::Attribute) {
         for_each_kind!(self, f,
-                       ByVal, NoAlias, NoCapture, NonNull, ReadOnly, SExt, StructRet, ZExt, InReg)
+                       NoAlias, NoCapture, NonNull, ReadOnly, SExt, StructRet, ZExt, InReg)
     }
 }
 
 pub trait ArgAttributesExt {
-    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value);
-    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value);
+    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value, ty: Option<&Type>);
+    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value, ty: Option<&Type>);
 }
 
 impl ArgAttributesExt for ArgAttributes {
-    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value) {
+    fn apply_llfn(&self, idx: AttributePlace, llfn: &Value, ty: Option<&Type>) {
         let mut regular = self.regular;
         unsafe {
             let deref = self.pointee_size.bytes();
@@ -65,11 +65,14 @@ impl ArgAttributesExt for ArgAttributes {
                                                idx.as_uint(),
                                                align.bytes() as u32);
             }
+            if regular.contains(ArgAttribute::ByVal) {
+                llvm::LLVMRustAddByValAttr(llfn, idx.as_uint(), ty.unwrap());
+            }
             regular.for_each_kind(|attr| attr.apply_llfn(idx, llfn));
         }
     }
 
-    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value) {
+    fn apply_callsite(&self, idx: AttributePlace, callsite: &Value, ty: Option<&Type>) {
         let mut regular = self.regular;
         unsafe {
             let deref = self.pointee_size.bytes();
@@ -90,6 +93,9 @@ impl ArgAttributesExt for ArgAttributes {
                                                        idx.as_uint(),
                                                        align.bytes() as u32);
             }
+            if regular.contains(ArgAttribute::ByVal) {
+                llvm::LLVMRustAddByValCallSiteAttr(callsite, idx.as_uint(), ty.unwrap());
+            }
             regular.for_each_kind(|attr| attr.apply_callsite(idx, callsite));
         }
     }
@@ -298,7 +304,7 @@ pub trait FnTypeLlvmExt<'tcx> {
     fn llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
     fn ptr_to_llvm_type(&self, cx: &CodegenCx<'ll, 'tcx>) -> &'ll Type;
     fn llvm_cconv(&self) -> llvm::CallConv;
-    fn apply_attrs_llfn(&self, llfn: &'ll Value);
+    fn apply_attrs_llfn(&self, cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value);
     fn apply_attrs_callsite(&self, bx: &mut Builder<'a, 'll, 'tcx>, callsite: &'ll Value);
 }
 
@@ -384,51 +390,51 @@ impl<'tcx> FnTypeLlvmExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
         }
     }
 
-    fn apply_attrs_llfn(&self, llfn: &'ll Value) {
+    fn apply_attrs_llfn(&self, cx: &CodegenCx<'ll, 'tcx>, llfn: &'ll Value) {
         let mut i = 0;
-        let mut apply = |attrs: &ArgAttributes| {
-            attrs.apply_llfn(llvm::AttributePlace::Argument(i), llfn);
+        let mut apply = |attrs: &ArgAttributes, ty: Option<&Type>| {
+            attrs.apply_llfn(llvm::AttributePlace::Argument(i), llfn, ty);
             i += 1;
         };
         match self.ret.mode {
             PassMode::Direct(ref attrs) => {
-                attrs.apply_llfn(llvm::AttributePlace::ReturnValue, llfn);
+                attrs.apply_llfn(llvm::AttributePlace::ReturnValue, llfn, None);
             }
-            PassMode::Indirect(ref attrs, _) => apply(attrs),
+            PassMode::Indirect(ref attrs, _) => apply(attrs, Some(self.ret.layout.llvm_type(cx))),
             _ => {}
         }
         for arg in &self.args {
             if arg.pad.is_some() {
-                apply(&ArgAttributes::new());
+                apply(&ArgAttributes::new(), None);
             }
             match arg.mode {
                 PassMode::Ignore(_) => {}
                 PassMode::Direct(ref attrs) |
-                PassMode::Indirect(ref attrs, None) => apply(attrs),
+                PassMode::Indirect(ref attrs, None) => apply(attrs, Some(arg.layout.llvm_type(cx))),
                 PassMode::Indirect(ref attrs, Some(ref extra_attrs)) => {
-                    apply(attrs);
-                    apply(extra_attrs);
+                    apply(attrs, None);
+                    apply(extra_attrs, None);
                 }
                 PassMode::Pair(ref a, ref b) => {
-                    apply(a);
-                    apply(b);
+                    apply(a, None);
+                    apply(b, None);
                 }
-                PassMode::Cast(_) => apply(&ArgAttributes::new()),
+                PassMode::Cast(_) => apply(&ArgAttributes::new(), None),
             }
         }
     }
 
     fn apply_attrs_callsite(&self, bx: &mut Builder<'a, 'll, 'tcx>, callsite: &'ll Value) {
         let mut i = 0;
-        let mut apply = |attrs: &ArgAttributes| {
-            attrs.apply_callsite(llvm::AttributePlace::Argument(i), callsite);
+        let mut apply = |attrs: &ArgAttributes, ty: Option<&Type>| {
+            attrs.apply_callsite(llvm::AttributePlace::Argument(i), callsite, ty);
             i += 1;
         };
         match self.ret.mode {
             PassMode::Direct(ref attrs) => {
-                attrs.apply_callsite(llvm::AttributePlace::ReturnValue, callsite);
+                attrs.apply_callsite(llvm::AttributePlace::ReturnValue, callsite, None);
             }
-            PassMode::Indirect(ref attrs, _) => apply(attrs),
+            PassMode::Indirect(ref attrs, _) => apply(attrs, Some(self.ret.layout.llvm_type(bx))),
             _ => {}
         }
         if let layout::Abi::Scalar(ref scalar) = self.ret.layout.abi {
@@ -446,21 +452,21 @@ impl<'tcx> FnTypeLlvmExt<'tcx> for FnType<'tcx, Ty<'tcx>> {
         }
         for arg in &self.args {
             if arg.pad.is_some() {
-                apply(&ArgAttributes::new());
+                apply(&ArgAttributes::new(), None);
             }
             match arg.mode {
                 PassMode::Ignore(_) => {}
                 PassMode::Direct(ref attrs) |
-                PassMode::Indirect(ref attrs, None) => apply(attrs),
+                PassMode::Indirect(ref attrs, None) => apply(attrs, Some(arg.layout.llvm_type(bx))),
                 PassMode::Indirect(ref attrs, Some(ref extra_attrs)) => {
-                    apply(attrs);
-                    apply(extra_attrs);
+                    apply(attrs, None);
+                    apply(extra_attrs, None);
                 }
                 PassMode::Pair(ref a, ref b) => {
-                    apply(a);
-                    apply(b);
+                    apply(a, None);
+                    apply(b, None);
                 }
-                PassMode::Cast(_) => apply(&ArgAttributes::new()),
+                PassMode::Cast(_) => apply(&ArgAttributes::new(), None),
             }
         }
 

src/librustc_codegen_llvm/attributes.rs

@@ -119,6 +119,29 @@ pub fn set_probestack(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {
         const_cstr!("probe-stack"), const_cstr!("__rust_probestack"));
 }
 
+fn translate_obsolete_target_features(feature: &str) -> &str {
+    const LLVM9_FEATURE_CHANGES: &[(&str, &str)] = &[
+        ("+fp-only-sp", "-fp64"),
+        ("-fp-only-sp", "+fp64"),
+        ("+d16", "-d32"),
+        ("-d16", "+d32"),
+    ];
+    if llvm_util::get_major_version() >= 9 {
+        for &(old, new) in LLVM9_FEATURE_CHANGES {
+            if feature == old {
+                return new;
+            }
+        }
+    } else {
+        for &(old, new) in LLVM9_FEATURE_CHANGES {
+            if feature == new {
+                return old;
+            }
+        }
+    }
+    feature
+}
+
 pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {
     const RUSTC_SPECIFIC_FEATURES: &[&str] = &[
         "crt-static",
@@ -129,6 +152,7 @@ pub fn llvm_target_features(sess: &Session) -> impl Iterator<Item = &str> {
     sess.target.target.options.features.split(',')
         .chain(cmdline)
         .filter(|l| !l.is_empty())
+        .map(translate_obsolete_target_features)
 }
 
 pub fn apply_target_cpu_attr(cx: &CodegenCx<'ll, '_>, llfn: &'ll Value) {

src/librustc_codegen_llvm/common.rs

@@ -249,6 +249,10 @@ impl ConstMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         self.const_uint(self.type_i8(), i as u64)
     }
 
+    fn const_real(&self, t: &'ll Type, val: f64) -> &'ll Value {
+        unsafe { llvm::LLVMConstReal(t, val) }
+    }
+
     fn const_struct(
         &self,
         elts: &[&'ll Value],

src/librustc_codegen_llvm/context.rs

@@ -1,5 +1,6 @@
 use crate::attributes;
 use crate::llvm;
+use crate::llvm_util;
 use crate::debuginfo;
 use crate::value::Value;
 use rustc::dep_graph::DepGraphSafe;
@@ -140,6 +141,11 @@ pub fn is_pie_binary(sess: &Session) -> bool {
     !is_any_library(sess) && get_reloc_model(sess) == llvm::RelocMode::PIC
 }
 
+fn strip_function_ptr_alignment(data_layout: String) -> String {
+    // FIXME: Make this more general.
+    data_layout.replace("-Fi8-", "-")
+}
+
 pub unsafe fn create_module(
     tcx: TyCtxt<'_>,
     llcx: &'ll llvm::Context,
@@ -149,14 +155,19 @@ pub unsafe fn create_module(
     let mod_name = SmallCStr::new(mod_name);
     let llmod = llvm::LLVMModuleCreateWithNameInContext(mod_name.as_ptr(), llcx);
 
+    let mut target_data_layout = sess.target.target.data_layout.clone();
+    if llvm_util::get_major_version() < 9 {
+        target_data_layout = strip_function_ptr_alignment(target_data_layout);
+    }
+
     // Ensure the data-layout values hardcoded remain the defaults.
     if sess.target.target.options.is_builtin {
         let tm = crate::back::write::create_informational_target_machine(&tcx.sess, false);
         llvm::LLVMRustSetDataLayoutFromTargetMachine(llmod, tm);
         llvm::LLVMRustDisposeTargetMachine(tm);
 
-        let data_layout = llvm::LLVMGetDataLayout(llmod);
-        let data_layout = str::from_utf8(CStr::from_ptr(data_layout).to_bytes())
+        let llvm_data_layout = llvm::LLVMGetDataLayout(llmod);
+        let llvm_data_layout = str::from_utf8(CStr::from_ptr(llvm_data_layout).to_bytes())
             .ok().expect("got a non-UTF8 data-layout from LLVM");
 
         // Unfortunately LLVM target specs change over time, and right now we
@@ -177,16 +188,16 @@ pub unsafe fn create_module(
         let cfg_llvm_root = option_env!("CFG_LLVM_ROOT").unwrap_or("");
         let custom_llvm_used = cfg_llvm_root.trim() != "";
 
-        if !custom_llvm_used && sess.target.target.data_layout != data_layout {
+        if !custom_llvm_used && target_data_layout != llvm_data_layout {
             bug!("data-layout for builtin `{}` target, `{}`, \
                   differs from LLVM default, `{}`",
                  sess.target.target.llvm_target,
-                 sess.target.target.data_layout,
-                 data_layout);
+                 target_data_layout,
+                 llvm_data_layout);
         }
     }
 
-    let data_layout = SmallCStr::new(&sess.target.target.data_layout);
+    let data_layout = SmallCStr::new(&target_data_layout);
     llvm::LLVMSetDataLayout(llmod, data_layout.as_ptr());
 
     let llvm_target = SmallCStr::new(&sess.target.target.llvm_target);

src/librustc_codegen_llvm/declare.rs

@@ -107,7 +107,7 @@ impl DeclareMethods<'tcx> for CodegenCx<'ll, 'tcx> {
             llvm::Attribute::NoReturn.apply_llfn(Function, llfn);
         }
 
-        fty.apply_attrs_llfn(llfn);
+        fty.apply_attrs_llfn(self, llfn);
 
         llfn
     }

src/librustc_codegen_llvm/intrinsic.rs

@@ -1663,9 +1663,10 @@ fn generic_simd_intrinsic(
                             acc
                         } else {
                             // unordered arithmetic reductions do not:
+                            let identity_acc = if $name.contains("mul") { 1.0 } else { 0.0 };
                             match f.bit_width() {
-                                32 => bx.const_undef(bx.type_f32()),
-                                64 => bx.const_undef(bx.type_f64()),
+                                32 => bx.const_real(bx.type_f32(), identity_acc),
+                                64 => bx.const_real(bx.type_f64(), identity_acc),
                                 v => {
                                     return_error!(r#"
 unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,

src/librustc_codegen_llvm/llvm/ffi.rs

@@ -715,6 +715,7 @@ extern "C" {
     // Operations on scalar constants
     pub fn LLVMConstInt(IntTy: &Type, N: c_ulonglong, SignExtend: Bool) -> &Value;
     pub fn LLVMConstIntOfArbitraryPrecision(IntTy: &Type, Wn: c_uint, Ws: *const u64) -> &Value;
+    pub fn LLVMConstReal(RealTy: &Type, N: f64) -> &Value;
     pub fn LLVMConstIntGetZExtValue(ConstantVal: &Value) -> c_ulonglong;
     pub fn LLVMRustConstInt128Get(ConstantVal: &Value, SExt: bool,
                                   high: &mut u64, low: &mut u64) -> bool;
@@ -794,6 +795,7 @@ extern "C" {
     pub fn LLVMRustAddAlignmentAttr(Fn: &Value, index: c_uint, bytes: u32);
     pub fn LLVMRustAddDereferenceableAttr(Fn: &Value, index: c_uint, bytes: u64);
     pub fn LLVMRustAddDereferenceableOrNullAttr(Fn: &Value, index: c_uint, bytes: u64);
+    pub fn LLVMRustAddByValAttr(Fn: &Value, index: c_uint, ty: &Type);
     pub fn LLVMRustAddFunctionAttribute(Fn: &Value, index: c_uint, attr: Attribute);
     pub fn LLVMRustAddFunctionAttrStringValue(Fn: &Value,
                                               index: c_uint,
@@ -824,6 +826,7 @@ extern "C" {
     pub fn LLVMRustAddDereferenceableOrNullCallSiteAttr(Instr: &Value,
                                                         index: c_uint,
                                                         bytes: u64);
+    pub fn LLVMRustAddByValCallSiteAttr(Instr: &Value, index: c_uint, ty: &Type);
 
     // Operations on load/store instructions (only)
     pub fn LLVMSetVolatile(MemoryAccessInst: &Value, volatile: Bool);

src/librustc_codegen_ssa/traits/consts.rs

@@ -17,6 +17,7 @@ pub trait ConstMethods<'tcx>: BackendTypes {
     fn const_u64(&self, i: u64) -> Self::Value;
     fn const_usize(&self, i: u64) -> Self::Value;
     fn const_u8(&self, i: u8) -> Self::Value;
+    fn const_real(&self, t: Self::Type, val: f64) -> Self::Value;
 
     fn const_struct(&self, elts: &[Self::Value], packed: bool) -> Self::Value;
 

src/librustc_target/spec/arm_linux_androideabi.rs

@@ -11,7 +11,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "android".to_string(),
         target_env: String::new(),

src/librustc_target/spec/arm_unknown_linux_gnueabi.rs

@@ -8,7 +8,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
         target_env: "gnu".to_string(),

src/librustc_target/spec/arm_unknown_linux_gnueabihf.rs

@@ -8,7 +8,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
         target_env: "gnu".to_string(),

src/librustc_target/spec/arm_unknown_linux_musleabi.rs

@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
         target_env: "musl".to_string(),

src/librustc_target/spec/arm_unknown_linux_musleabihf.rs

@@ -15,7 +15,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
         target_env: "musl".to_string(),

src/librustc_target/spec/armebv7r_none_eabi.rs

@@ -9,7 +9,7 @@ pub fn target() -> TargetResult {
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "E-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "E-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "none".to_string(),
         target_env: "".to_string(),

src/librustc_target/spec/armebv7r_none_eabihf.rs

@@ -9,7 +9,7 @@ pub fn target() -> TargetResult {
         target_endian: "big".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "E-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "E-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "none".to_string(),
         target_env: String::new(),
@@ -21,7 +21,7 @@ pub fn target() -> TargetResult {
             linker: Some("rust-lld".to_owned()),
             relocation_model: "static".to_string(),
             panic_strategy: PanicStrategy::Abort,
-            features: "+vfp3,+d16,+fp-only-sp".to_string(),
+            features: "+vfp3,-d32,-fp16".to_string(),
             max_atomic_width: Some(32),
             abi_blacklist: super::arm_base::abi_blacklist(),
             emit_debug_gdb_scripts: false,

src/librustc_target/spec/armv4t_unknown_linux_gnueabi.rs

@@ -7,7 +7,7 @@ pub fn target() -> TargetResult {
         target_endian: "little".to_string(),
         target_pointer_width: "32".to_string(),
         target_c_int_width: "32".to_string(),
-        data_layout: "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
+        data_layout: "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64".to_string(),
         arch: "arm".to_string(),
         target_os: "linux".to_string(),
         target_env: "gnu".to_string(),