Auto merge of #94402 - erikdesjardins:revert-coldland, r=nagisa

Revert "Auto merge of #92419 - erikdesjardins:coldland, r=nagisa"

Should fix (untested) #94390

Reopens #46515, #87055

r? `@ehuss`

compiler/rustc_codegen_gcc/src/builder.rs

@@ -1403,7 +1403,7 @@ impl<'a, 'gcc, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'gcc, 'tcx> {
         self.cx
     }
 
-    fn apply_attrs_to_cleanup_callsite(&mut self, _llret: RValue<'gcc>) {
+    fn do_not_inline(&mut self, _llret: RValue<'gcc>) {
         unimplemented!();
     }
 

compiler/rustc_codegen_llvm/src/builder.rs

@@ -23,7 +23,6 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
 use rustc_target::abi::{self, call::FnAbi, Align, Size, WrappingRange};
 use rustc_target::spec::{HasTargetSpec, Target};
-use smallvec::SmallVec;
 use std::borrow::Cow;
 use std::ffi::CStr;
 use std::iter;
@@ -1179,19 +1178,9 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
         unsafe { llvm::LLVMBuildZExt(self.llbuilder, val, dest_ty, UNNAMED) }
     }
 
-    fn apply_attrs_to_cleanup_callsite(&mut self, llret: &'ll Value) {
+    fn do_not_inline(&mut self, llret: &'ll Value) {
-        let mut attrs = SmallVec::<[_; 2]>::new();
+        let noinline = llvm::AttributeKind::NoInline.create_attr(self.llcx);
-
+        attributes::apply_to_callsite(llret, llvm::AttributePlace::Function, &[noinline]);
-        // Cleanup is always the cold path.
-        attrs.push(llvm::AttributeKind::Cold.create_attr(self.llcx));
-
-        // In LLVM versions with deferred inlining (currently, system LLVM < 14),
-        // inlining drop glue can lead to exponential size blowup, see #41696 and #92110.
-        if !llvm_util::is_rust_llvm() && llvm_util::get_version() < (14, 0, 0) {
-            attrs.push(llvm::AttributeKind::NoInline.create_attr(self.llcx));
-        }
-
-        attributes::apply_to_callsite(llret, llvm::AttributePlace::Function, &attrs);
     }
 }
 

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -1933,8 +1933,6 @@ extern "C" {
     pub fn LLVMRustVersionMinor() -> u32;
     pub fn LLVMRustVersionPatch() -> u32;
 
-    pub fn LLVMRustIsRustLLVM() -> bool;
-
     /// Add LLVM module flags.
     ///
     /// In order for Rust-C LTO to work, module flags must be compatible with Clang. What

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -257,12 +257,6 @@ pub fn get_version() -> (u32, u32, u32) {
     }
 }
 
-/// Returns `true` if this LLVM is Rust's bundled LLVM (and not system LLVM).
-pub fn is_rust_llvm() -> bool {
-    // Can be called without initializing LLVM
-    unsafe { llvm::LLVMRustIsRustLLVM() }
-}
-
 pub fn print_passes() {
     // Can be called without initializing LLVM
     unsafe {

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -166,7 +166,7 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
                 bx.invoke(fn_ty, fn_ptr, &llargs, ret_llbb, unwind_block, self.funclet(fx));
             bx.apply_attrs_callsite(&fn_abi, invokeret);
             if fx.mir[self.bb].is_cleanup {
-                bx.apply_attrs_to_cleanup_callsite(invokeret);
+                bx.do_not_inline(invokeret);
             }
 
             if let Some((ret_dest, target)) = destination {
@@ -178,7 +178,11 @@ impl<'a, 'tcx> TerminatorCodegenHelper<'tcx> {
             let llret = bx.call(fn_ty, fn_ptr, &llargs, self.funclet(fx));
             bx.apply_attrs_callsite(&fn_abi, llret);
             if fx.mir[self.bb].is_cleanup {
-                bx.apply_attrs_to_cleanup_callsite(llret);
+                // Cleanup is always the cold path. Don't inline
+                // drop glue. Also, when there is a deeply-nested
+                // struct, there are "symmetry" issues that cause
+                // exponential inlining - see issue #41696.
+                bx.do_not_inline(llret);
             }
 
             if let Some((ret_dest, target)) = destination {
@@ -1444,7 +1448,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
             let llret = bx.call(fn_ty, fn_ptr, &[], None);
             bx.apply_attrs_callsite(&fn_abi, llret);
-            bx.apply_attrs_to_cleanup_callsite(llret);
+            bx.do_not_inline(llret);
 
             bx.unreachable();
 

compiler/rustc_codegen_ssa/src/traits/builder.rs

@@ -479,5 +479,5 @@ pub trait BuilderMethods<'a, 'tcx>:
     ) -> Self::Value;
     fn zext(&mut self, val: Self::Value, dest_ty: Self::Type) -> Self::Value;
 
-    fn apply_attrs_to_cleanup_callsite(&mut self, llret: Self::Value);
+    fn do_not_inline(&mut self, llret: Self::Value);
 }

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -694,14 +694,6 @@ extern "C" uint32_t LLVMRustVersionMinor() { return LLVM_VERSION_MINOR; }
 
 extern "C" uint32_t LLVMRustVersionMajor() { return LLVM_VERSION_MAJOR; }
 
-extern "C" bool LLVMRustIsRustLLVM() {
-#ifdef LLVM_RUSTLLVM
-  return true;
-#else
-  return false;
-#endif
-}
-
 extern "C" void LLVMRustAddModuleFlag(
     LLVMModuleRef M,
     Module::ModFlagBehavior MergeBehavior,

src/test/codegen/unwind-landingpad-cold.rs

@@ -1,15 +0,0 @@
-// no-system-llvm: needs #92110
-// compile-flags: -Cno-prepopulate-passes
-#![crate_type = "lib"]
-
-// This test checks that drop calls in unwind landing pads
-// get the `cold` attribute.
-
-// CHECK-LABEL: @check_cold
-// CHECK: {{(call|invoke) void .+}}drop_in_place{{.+}} [[ATTRIBUTES:#[0-9]+]]
-// CHECK: attributes [[ATTRIBUTES]] = { cold }
-#[no_mangle]
-pub fn check_cold(f: fn(), x: Box<u32>) {
-    // this may unwind
-    f();
-}

src/test/codegen/unwind-landingpad-inline.rs

@@ -1,37 +0,0 @@
-// no-system-llvm: needs #92110 + patch for Rust alloc/dealloc functions
-// compile-flags: -Copt-level=3
-#![crate_type = "lib"]
-
-// This test checks that we can inline drop_in_place in
-// unwind landing pads.
-
-// Without inlining, the box pointers escape via the call to drop_in_place,
-// and LLVM will not optimize out the pointer comparison.
-// With inlining, everything should be optimized out.
-// See https://github.com/rust-lang/rust/issues/46515
-// CHECK-LABEL: @check_no_escape_in_landingpad
-// CHECK: start:
-// CHECK-NEXT: ret void
-#[no_mangle]
-pub fn check_no_escape_in_landingpad(f: fn()) {
-    let x = &*Box::new(0);
-    let y = &*Box::new(0);
-
-    if x as *const _ == y as *const _ {
-        f();
-    }
-}
-
-// Without inlining, the compiler can't tell that
-// dropping an empty string (in a landing pad) does nothing.
-// With inlining, the landing pad should be optimized out.
-// See https://github.com/rust-lang/rust/issues/87055
-// CHECK-LABEL: @check_eliminate_noop_drop
-// CHECK: start:
-// CHECK-NEXT: call void %g()
-// CHECK-NEXT: ret void
-#[no_mangle]
-pub fn check_eliminate_noop_drop(g: fn()) {
-    let _var = String::new();
-    g();
-}

src/test/codegen/vec-shrink-panik.rs

@@ -16,6 +16,14 @@ pub fn shrink_to_fit(vec: &mut Vec<u32>) {
 // CHECK-LABEL: @issue71861
 #[no_mangle]
 pub fn issue71861(vec: Vec<u32>) -> Box<[u32]> {
+    // CHECK-NOT: panic
+
+    // Call to panic_no_unwind in case of double-panic is expected,
+    // but other panics are not.
+    // CHECK: cleanup
+    // CHECK-NEXT: ; call core::panicking::panic_no_unwind
+    // CHECK-NEXT: panic_no_unwind
+
     // CHECK-NOT: panic
     vec.into_boxed_slice()
 }
@@ -23,6 +31,17 @@ pub fn issue71861(vec: Vec<u32>) -> Box<[u32]> {
 // CHECK-LABEL: @issue75636
 #[no_mangle]
 pub fn issue75636<'a>(iter: &[&'a str]) -> Box<[&'a str]> {
+    // CHECK-NOT: panic
+
+    // Call to panic_no_unwind in case of double-panic is expected,
+    // but other panics are not.
+    // CHECK: cleanup
+    // CHECK-NEXT: ; call core::panicking::panic_no_unwind
+    // CHECK-NEXT: panic_no_unwind
+
     // CHECK-NOT: panic
     iter.iter().copied().collect()
 }
+
+// CHECK: ; core::panicking::panic_no_unwind
+// CHECK: declare void @{{.*}}panic_no_unwind