Support -Z merge-functions with gcc and add stack-protector asm tests

compiler/rustc_codegen_gcc/src/gcc_util.rs

@@ -9,7 +9,9 @@ use rustc_codegen_ssa::target_features;
 use rustc_data_structures::smallvec::{SmallVec, smallvec};
 use rustc_session::config::NATIVE_CPU;
 use rustc_session::{EarlySession, Session};
-use rustc_target::spec::{Arch, RelocModel, StackProbeType, StackProtector, Target};
+use rustc_target::spec::{
+    Arch, MergeFunctions, RelocModel, StackProbeType, StackProtector, Target,
+};
 
 fn gcc_features_by_flags(sess: &EarlySession, features: &mut Vec<String>) {
     target_features::retpoline_features_by_flags(sess, features);
@@ -220,6 +222,16 @@ pub fn new_context<'gcc>(sess: &Session) -> Context<'gcc> {
         StackProtector::None => (),
     }
 
+    match sess.merge_functions() {
+        MergeFunctions::Disabled => {
+            context.add_command_line_option("-fno-ipa-icf-functions");
+        }
+        // GCC always merges functions with trampolines rather than aliases, so we don't
+        // need to differentiate MergeFunctions::Trampolines and MergeFunctions::Aliases
+        // as trampolines are allowed either way.
+        MergeFunctions::Trampolines | MergeFunctions::Aliases => {}
+    }
+
     match sess.target.stack_probes {
         StackProbeType::None => (),
         StackProbeType::Inline | StackProbeType::InlineOrCall { .. } => {

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -120,7 +120,7 @@ unsafe fn configure_llvm(sess: &EarlySession) {
             add("-generate-arange-section", false);
         }
 
-        match sess.opts.unstable_opts.merge_functions.unwrap_or(sess.target.merge_functions) {
+        match sess.merge_functions() {
             MergeFunctions::Disabled | MergeFunctions::Trampolines => {}
             MergeFunctions::Aliases => {
                 add("-mergefunc-use-aliases", false);

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -244,12 +244,7 @@ impl ModuleConfig {
             // backends (again, NVPTX). Therefore, allow targets to opt out of
             // the MergeFunctions pass, but otherwise keep the pass enabled (at
             // O2 and O3) since it can be useful for reducing code size.
-            merge_functions: match sess
-                .opts
-                .unstable_opts
-                .merge_functions
-                .unwrap_or(sess.target.merge_functions)
-            {
+            merge_functions: match sess.merge_functions() {
                 MergeFunctions::Disabled => false,
                 MergeFunctions::Trampolines | MergeFunctions::Aliases => {
                     use config::OptLevel::*;

compiler/rustc_session/src/options.rs

@@ -2643,6 +2643,7 @@ options! {
     maximal_hir_to_mir_coverage: bool = (false, parse_bool, [TRACKED],
         "save as much information as possible about the correspondence between MIR and HIR \
         as source scopes (default: no)"),
+    #[rustc_lint_opt_deny_field_access("use `Session::merge_functions` instead of this field")]
     merge_functions: Option<MergeFunctions> = (None, parse_merge_functions, [TRACKED],
         "control the operation of the MergeFunctions LLVM pass, taking \
         the same values as the target option of the same name"),

compiler/rustc_session/src/session.rs

@@ -28,9 +28,9 @@ use rustc_span::{RealFileName, Span, Symbol};
 use rustc_structures::{CrateType, Limit};
 use rustc_target::asm::InlineAsmArch;
 use rustc_target::spec::{
-    Arch, CfgAbi, CodeModel, DebuginfoKind, Os, PanicStrategy, RelocModel, RelroLevel,
-    SanitizerSet, SmallDataThresholdSupport, SplitDebuginfo, StackProtector, SymbolVisibility,
-    Target, TargetTuple, TlsModel, apple,
+    Arch, CfgAbi, CodeModel, DebuginfoKind, MergeFunctions, Os, PanicStrategy, RelocModel,
+    RelroLevel, SanitizerSet, SmallDataThresholdSupport, SplitDebuginfo, StackProtector,
+    SymbolVisibility, Target, TargetTuple, TlsModel, apple,
 };
 
 use crate::code_stats::CodeStats;
@@ -423,6 +423,10 @@ impl EarlySession {
             .sanitizer
             .combine_with_defaults(self.target.options.default_sanitizers)
     }
+
+    pub fn merge_functions(&self) -> MergeFunctions {
+        self.opts.unstable_opts.merge_functions.unwrap_or(self.target.merge_functions)
+    }
 }
 
 /// Some info about the backend, returned by `CodegenBackend::init` and put into the `Session`.

compiler/rustc_target/src/spec/mod.rs

@@ -927,8 +927,15 @@ impl ToJson for SmallDataThresholdSupport {
 
 crate::target_spec_enum! {
     pub enum MergeFunctions {
+        /// Disable function merging entirely.
         Disabled = "disabled",
+        /// Allow function merging via trampolines (i.e., functions can be implemented
+        /// in terms of a jump to an unrelated function with identical behavior), but
+        /// not via object-format-level global aliases.
         Trampolines = "trampolines",
+        /// (Default) allow function merging via either trampolines or (object format
+        /// level) global aliases. LLVM will normally use global aliases for merging, but
+        /// trampolines are also permissible.
         Aliases = "aliases",
     }
 

src/bootstrap/src/core/build_steps/test.rs

@@ -2040,6 +2040,12 @@ test!(BuildStd {
     default: false
 });
 
+test!(AssemblyGcc {
+    path: "tests/assembly-gcc",
+    mode: CompiletestMode::Assembly,
+    suite: "assembly-gcc",
+    default: true
+});
 test!(AssemblyLlvm {
     path: "tests/assembly-llvm",
     mode: CompiletestMode::Assembly,

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test.snap

@@ -23,6 +23,9 @@ expression: test
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage.snap

@@ -20,6 +20,9 @@ expression: test --skip=coverage
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_map.snap

@@ -23,6 +23,9 @@ expression: test --skip=coverage-map
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_coverage_run.snap

@@ -23,6 +23,9 @@ expression: test --skip=coverage-run
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_skip_tests_coverage.snap

@@ -20,6 +20,9 @@ expression: test --skip=tests/coverage
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_tests.snap

@@ -20,6 +20,9 @@ expression: test tests
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/cli_paths/snapshots/x_test_tests_skip_coverage.snap

@@ -17,6 +17,9 @@ expression: test tests --skip=coverage
 [Test] test::CodegenUnits
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/codegen-units)
+[Test] test::AssemblyGcc
+    targets: [aarch64-unknown-linux-gnu]
+    - Suite(tests/assembly-gcc)
 [Test] test::AssemblyLlvm
     targets: [aarch64-unknown-linux-gnu]
     - Suite(tests/assembly-llvm)

src/bootstrap/src/core/builder/mod.rs

@@ -886,6 +886,7 @@ impl<'a> Builder<'a> {
                 test::MirOpt,
                 test::CodegenLlvm,
                 test::CodegenUnits,
+                test::AssemblyGcc,
                 test::AssemblyLlvm,
                 test::Incremental,
                 test::Debuginfo,

src/bootstrap/src/core/builder/tests.rs

@@ -1943,6 +1943,7 @@ mod snapshot {
         [test] compiletest-mir-opt 1 <host>
         [test] compiletest-codegen-llvm 1 <host>
         [test] compiletest-codegen-units 1 <host>
+        [test] compiletest-assembly-gcc 1 <host>
         [test] compiletest-assembly-llvm 1 <host>
         [test] compiletest-incremental 1 <host>
         [test] compiletest-debuginfo 1 <host>
@@ -2124,6 +2125,7 @@ mod snapshot {
         [test] compiletest-mir-opt 2 <host>
         [test] compiletest-codegen-llvm 2 <host>
         [test] compiletest-codegen-units 2 <host>
+        [test] compiletest-assembly-gcc 2 <host>
         [test] compiletest-assembly-llvm 2 <host>
         [test] compiletest-incremental 2 <host>
         [test] compiletest-debuginfo 2 <host>

src/tools/compiletest/src/common.rs

@@ -60,6 +60,7 @@ impl TestMode {
 string_enum! {
     #[derive(Clone, Copy, PartialEq, Debug)]
     pub(crate) enum TestSuite {
+        AssemblyGcc => "assembly-gcc",
         AssemblyLlvm => "assembly-llvm",
         CodegenLlvm => "codegen-llvm",
         CodegenUnits => "codegen-units",

src/tools/compiletest/src/runtest.rs

@@ -1604,7 +1604,8 @@ impl<'test> TestCx<'test> {
             // Exhaustively match all other suites.
             // Note that some suites never actually use this method, so the
             // return value for those suites is not necessarily meaningful.
-            TestSuite::AssemblyLlvm
+            TestSuite::AssemblyGcc
+            | TestSuite::AssemblyLlvm
             | TestSuite::BuildStd
             | TestSuite::CodegenLlvm
             | TestSuite::CodegenUnits