Auto merge of #51966 - alexcrichton:llvm7, r=michaelwoerister

Upgrade to LLVM's master branch (LLVM 7)

### Current status

~~Blocked on a [performance regression](https://github.com/rust-lang/rust/pull/51966#issuecomment-402320576). The performance regression has an [upstream LLVM issue](https://bugs.llvm.org/show_bug.cgi?id=38047) and has also [been bisected](https://reviews.llvm.org/D44282) to an LLVM revision.~~

Ready to merge!

---

This commit upgrades the main LLVM submodule to LLVM's current master branch.
The LLD submodule is updated in tandem as well as compiler-builtins.

Along the way support was also added for LLVM 7's new features. This primarily
includes the support for custom section concatenation natively in LLD so we now
add wasm custom sections in LLVM IR rather than having custom support in rustc
itself for doing so.

Some other miscellaneous changes are:

* We now pass `--gc-sections` to `wasm-ld`
* The optimization level is now passed to `wasm-ld`
* A `--stack-first` option is passed to LLD to have stack overflow always cause
  a trap instead of corrupting static data
* The wasm target for LLVM switched to `wasm32-unknown-unknown`.
* The syntax for aligned pointers has changed in LLVM IR and tests are updated
  to reflect this.
* ~~The `thumbv6m-none-eabi` target is disabled due to an [LLVM bug][llbug]~~

Nowadays we've been mostly only upgrading whenever there's a major release of
LLVM but enough changes have been happening on the wasm target that there's been
growing motivation for quite some time now to upgrade out version of LLD. To
upgrade LLD, however, we need to upgrade LLVM to avoid needing to build yet
another version of LLVM on the builders.

The revision of LLVM in use here is arbitrarily chosen. We will likely need to
continue to update it over time if and when we discover bugs. Once LLVM 7 is
fully released we can switch to that channel as well.

[llbug]: https://bugs.llvm.org/show_bug.cgi?id=37382

cc #50543

6 files changed, 26 insertions, 20 deletions

diff --git a/src/test/codegen/align-struct.rs b/src/test/codegen/align-struct.rs
index f306608f432..bf119da2e82 100644
--- a/src/test/codegen/align-struct.rs
+++ b/src/test/codegen/align-struct.rs
@@ -10,6 +10,7 @@
 
 // compile-flags: -C no-prepopulate-passes
 // ignore-tidy-linelength
+// min-llvm-version 7.0
 
 #![crate_type = "lib"]
 
@@ -42,7 +43,7 @@ pub enum Enum64 {
 #[no_mangle]
 pub fn align64(i : i32) -> Align64 {
 // CHECK: %a64 = alloca %Align64, align 64
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 64, i32 64, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 64 %{{.*}}, i8* align 64 %{{.*}}, i{{[0-9]+}} 64, i1 false)
     let a64 = Align64(i);
     a64
 }
diff --git a/src/test/codegen/consts.rs b/src/test/codegen/consts.rs
index 007fb7f4596..30fffbb769b 100644
--- a/src/test/codegen/consts.rs
+++ b/src/test/codegen/consts.rs
@@ -10,6 +10,7 @@
 
 // compile-flags: -C no-prepopulate-passes
 // ignore-tidy-linelength
+// min-llvm-version 7.0
 
 #![crate_type = "lib"]
 
@@ -54,7 +55,7 @@ pub fn inline_enum_const() -> E<i8, i16> {
 #[no_mangle]
 pub fn low_align_const() -> E<i16, [i16; 3]> {
 // Check that low_align_const and high_align_const use the same constant
-// CHECK: i8* getelementptr inbounds (<{ [8 x i8] }>, <{ [8 x i8] }>* [[LOW_HIGH]], i32 0, i32 0, i32 0),
+// CHECK: i8* align 2 getelementptr inbounds (<{ [8 x i8] }>, <{ [8 x i8] }>* [[LOW_HIGH]], i32 0, i32 0, i32 0),
     *&E::A(0)
 }
 
@@ -62,6 +63,6 @@ pub fn low_align_const() -> E<i16, [i16; 3]> {
 #[no_mangle]
 pub fn high_align_const() -> E<i16, i32> {
 // Check that low_align_const and high_align_const use the same constant
-// CHECK: i8* getelementptr inbounds (<{ [8 x i8] }>, <{ [8 x i8] }>* [[LOW_HIGH]], i32 0, i32 0, i32 0),
+// CHECK: i8* align 4 getelementptr inbounds (<{ [8 x i8] }>, <{ [8 x i8] }>* [[LOW_HIGH]], i32 0, i32 0, i32 0),
     *&E::A(0)
 }
diff --git a/src/test/codegen/packed.rs b/src/test/codegen/packed.rs
index 0693eae7d78..10dd12909b6 100644
--- a/src/test/codegen/packed.rs
+++ b/src/test/codegen/packed.rs
@@ -8,7 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-tidy-linelength
 // compile-flags: -C no-prepopulate-passes
+// min-llvm-version 7.0
 
 #![crate_type = "lib"]
 #![feature(repr_packed)]
@@ -63,7 +65,7 @@ pub struct BigPacked2 {
 pub fn call_pkd1(f: fn() -> Array) -> BigPacked1 {
 // CHECK: [[ALLOCA:%[_a-z0-9]+]] = alloca %Array
 // CHECK: call void %{{.*}}(%Array* noalias nocapture sret dereferenceable(32) [[ALLOCA]])
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 32, i32 1, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 1 %{{.*}}, i8* align 1 %{{.*}}, i{{[0-9]+}} 32, i1 false)
     // check that calls whose destination is a field of a packed struct
     // go through an alloca rather than calling the function with an
     // unaligned destination.
@@ -75,7 +77,7 @@ pub fn call_pkd1(f: fn() -> Array) -> BigPacked1 {
 pub fn call_pkd2(f: fn() -> Array) -> BigPacked2 {
 // CHECK: [[ALLOCA:%[_a-z0-9]+]] = alloca %Array
 // CHECK: call void %{{.*}}(%Array* noalias nocapture sret dereferenceable(32) [[ALLOCA]])
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 32, i32 2, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 2 %{{.*}}, i8* align 2 %{{.*}}, i{{[0-9]+}} 32, i1 false)
     // check that calls whose destination is a field of a packed struct
     // go through an alloca rather than calling the function with an
     // unaligned destination.
@@ -93,14 +95,14 @@ pub struct Packed2Pair(u8, u32);
 // CHECK-LABEL: @pkd1_pair
 #[no_mangle]
 pub fn pkd1_pair(pair1: &mut Packed1Pair, pair2: &mut Packed1Pair) {
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 5, i32 1, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 1 %{{.*}}, i8* align 1 %{{.*}}, i{{[0-9]+}} 5, i1 false)
     *pair2 = *pair1;
 }
 
 // CHECK-LABEL: @pkd2_pair
 #[no_mangle]
 pub fn pkd2_pair(pair1: &mut Packed2Pair, pair2: &mut Packed2Pair) {
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 6, i32 2, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 2 %{{.*}}, i8* align 2 %{{.*}}, i{{[0-9]+}} 6, i1 false)
     *pair2 = *pair1;
 }
 
@@ -115,14 +117,14 @@ pub struct Packed2NestedPair((u32, u32));
 // CHECK-LABEL: @pkd1_nested_pair
 #[no_mangle]
 pub fn pkd1_nested_pair(pair1: &mut Packed1NestedPair, pair2: &mut Packed1NestedPair) {
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 8, i32 1, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 1 %{{.*}}, i8* align 1 %{{.*}}, i{{[0-9]+}} 8, i1 false)
     *pair2 = *pair1;
 }
 
 // CHECK-LABEL: @pkd2_nested_pair
 #[no_mangle]
 pub fn pkd2_nested_pair(pair1: &mut Packed2NestedPair, pair2: &mut Packed2NestedPair) {
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* %{{.*}}, i8* %{{.*}}, i{{[0-9]+}} 8, i32 2, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 2 %{{.*}}, i8* align 2 %{{.*}}, i{{[0-9]+}} 8, i1 false)
     *pair2 = *pair1;
 }
 
diff --git a/src/test/codegen/repeat-trusted-len.rs b/src/test/codegen/repeat-trusted-len.rs
index 8b3294281e9..8565335bd75 100644
--- a/src/test/codegen/repeat-trusted-len.rs
+++ b/src/test/codegen/repeat-trusted-len.rs
@@ -10,6 +10,7 @@
 
 // compile-flags: -O
 // ignore-tidy-linelength
+// min-llvm-version 7.0
 
 #![crate_type = "lib"]
 
@@ -23,6 +24,6 @@ pub fn helper(_: usize) {
 // CHECK-LABEL: @repeat_take_collect
 #[no_mangle]
 pub fn repeat_take_collect() -> Vec<u8> {
-// CHECK: call void @llvm.memset.p0i8.[[USIZE]](i8* {{(nonnull )?}}%{{[0-9]+}}, i8 42, [[USIZE]] 100000, i32 1, i1 false)
+// CHECK: call void @llvm.memset.p0i8.[[USIZE]](i8* {{(nonnull )?}}align 1 %{{[0-9]+}}, i8 42, [[USIZE]] 100000, i1 false)
     iter::repeat(42).take(100000).collect()
 }
diff --git a/src/test/codegen/simd-intrinsic-float-minmax.rs b/src/test/codegen/simd-intrinsic-float-minmax.rs
index d963c7e8ddf..16f86735c2e 100644
--- a/src/test/codegen/simd-intrinsic-float-minmax.rs
+++ b/src/test/codegen/simd-intrinsic-float-minmax.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 // ignore-emscripten
-// min-llvm-version 6.0
+// min-llvm-version 7.0
 
 // compile-flags: -C no-prepopulate-passes
 
@@ -34,10 +34,9 @@ pub unsafe fn fmin(a: f32x4, b: f32x4) -> f32x4 {
     simd_fmin(a, b)
 }
 
-// FIXME(49261)
-// // C_HECK-LABEL: @fmax
-// #[no_mangle]
-// pub unsafe fn fmax(a: f32x4, b: f32x4) -> f32x4 {
-// // C_HECK: call <4 x float> @llvm.maxnum.v4f32
-//     simd_fmax(a, b)
-// }
+// CHECK-LABEL: @fmax
+#[no_mangle]
+pub unsafe fn fmax(a: f32x4, b: f32x4) -> f32x4 {
+    // CHECK: call <4 x float> @llvm.maxnum.v4f32
+    simd_fmax(a, b)
+}
diff --git a/src/test/codegen/stores.rs b/src/test/codegen/stores.rs
index 08f5038fb18..0aaf00bfdbe 100644
--- a/src/test/codegen/stores.rs
+++ b/src/test/codegen/stores.rs
@@ -9,6 +9,8 @@
 // except according to those terms.
 
 // compile-flags: -C no-prepopulate-passes
+// ignore-tidy-linelength
+// min-llvm-version 7.0
 
 #![crate_type = "lib"]
 
@@ -29,7 +31,7 @@ pub fn small_array_alignment(x: &mut [i8; 4], y: [i8; 4]) {
 // CHECK: store i32 %0, i32* [[TMP]]
 // CHECK: [[Y8:%[0-9]+]] = bitcast [4 x i8]* %y to i8*
 // CHECK: [[TMP8:%[0-9]+]] = bitcast i32* [[TMP]] to i8*
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[Y8]], i8* [[TMP8]], i{{[0-9]+}} 4, i32 1, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 1 [[Y8]], i8* align 1 [[TMP8]], i{{[0-9]+}} 4, i1 false)
     *x = y;
 }
 
@@ -43,6 +45,6 @@ pub fn small_struct_alignment(x: &mut Bytes, y: Bytes) {
 // CHECK: store i32 %0, i32* [[TMP]]
 // CHECK: [[Y8:%[0-9]+]] = bitcast %Bytes* %y to i8*
 // CHECK: [[TMP8:%[0-9]+]] = bitcast i32* [[TMP]] to i8*
-// CHECK: call void @llvm.memcpy.{{.*}}(i8* [[Y8]], i8* [[TMP8]], i{{[0-9]+}} 4, i32 1, i1 false)
+// CHECK: call void @llvm.memcpy.{{.*}}(i8* align 1 [[Y8]], i8* align 1 [[TMP8]], i{{[0-9]+}} 4, i1 false)
     *x = y;
 }