build: Don't pass inherited PGO flags to GNU compilers (#1363)

Clang and GNU use different PGO libraries, so PGO flags inherited
from rustc should not automatically be passed to GNU compilers.

Fixes #1354

Author: mrkajetanp

src/flags.rs

@@ -174,26 +174,109 @@ impl<'this> RustcCodegenFlags<'this> {
             }
         };
 
-        match family {
-            ToolFamily::Clang { .. } | ToolFamily::Gnu => {
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mbranch-protection
-                if let Some(value) = self.branch_protection {
-                    push_if_supported(
-                        format!("-mbranch-protection={}", value.replace(",", "+")).into(),
-                    );
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mcmodel
-                if let Some(value) = self.code_model {
-                    push_if_supported(format!("-mcmodel={value}").into());
+        let clang_or_gnu =
+            matches!(family, ToolFamily::Clang { .. }) || matches!(family, ToolFamily::Gnu { .. });
+
+        // Flags shared between clang and gnu
+        if clang_or_gnu {
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mbranch-protection
+            if let Some(value) = self.branch_protection {
+                push_if_supported(
+                    format!("-mbranch-protection={}", value.replace(",", "+")).into(),
+                );
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mcmodel
+            if let Some(value) = self.code_model {
+                push_if_supported(format!("-mcmodel={value}").into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-vectorize
+            if self.no_vectorize_loops {
+                push_if_supported("-fno-vectorize".into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-slp-vectorize
+            if self.no_vectorize_slp {
+                push_if_supported("-fno-slp-vectorize".into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mguard
+            if let Some(value) = self.control_flow_guard {
+                let cc_val = match value {
+                    "y" | "yes" | "on" | "true" | "checks" => Some("cf"),
+                    "nochecks" => Some("cf-nochecks"),
+                    "n" | "no" | "off" | "false" => Some("none"),
+                    _ => None,
+                };
+                if let Some(cc_val) = cc_val {
+                    push_if_supported(format!("-mguard={cc_val}").into());
                 }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-vectorize
-                if self.no_vectorize_loops {
-                    push_if_supported("-fno-vectorize".into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-flto
+            if let Some(value) = self.lto {
+                let cc_val = match value {
+                    "y" | "yes" | "on" | "true" | "fat" => Some("full"),
+                    "thin" => Some("thin"),
+                    _ => None,
+                };
+                if let Some(cc_val) = cc_val {
+                    push_if_supported(format!("-flto={cc_val}").into());
                 }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-slp-vectorize
-                if self.no_vectorize_slp {
-                    push_if_supported("-fno-slp-vectorize".into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fPIC
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fPIE
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mdynamic-no-pic
+            if let Some(value) = self.relocation_model {
+                let cc_flag = match value {
+                    "pic" => Some("-fPIC"),
+                    "pie" => Some("-fPIE"),
+                    "dynamic-no-pic" => Some("-mdynamic-no-pic"),
+                    _ => None,
+                };
+                if let Some(cc_flag) = cc_flag {
+                    push_if_supported(cc_flag.into());
                 }
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fembed-bitcode
+            if let Some(value) = self.embed_bitcode {
+                let cc_val = if value { "all" } else { "off" };
+                push_if_supported(format!("-fembed-bitcode={cc_val}").into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-omit-frame-pointer
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fomit-frame-pointer
+            if let Some(value) = self.force_frame_pointers {
+                let cc_flag = if value {
+                    "-fno-omit-frame-pointer"
+                } else {
+                    "-fomit-frame-pointer"
+                };
+                push_if_supported(cc_flag.into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-dead_strip
+            if let Some(false) = self.link_dead_code {
+                push_if_supported("-dead_strip".into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mno-red-zone
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mred-zone
+            if let Some(value) = self.no_redzone {
+                let cc_flag = if value { "-mno-red-zone" } else { "-mred-zone" };
+                push_if_supported(cc_flag.into());
+            }
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-msoft-float
+            // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mno-soft-float
+            if let Some(value) = self.soft_float {
+                let cc_flag = if value {
+                    "-msoft-float"
+                } else {
+                    "-mno-soft-float"
+                };
+                push_if_supported(cc_flag.into());
+            }
+        }
+
+        // Compiler-exclusive flags
+        match family {
+            ToolFamily::Clang { .. } => {
+                // GNU and Clang compilers both support the same PGO flags, but they use different libraries and
+                // different formats for the profile files which are not compatible.
+                // clang and rustc both internally use llvm, so we want to inherit the PGO flags only for clang.
                 // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fprofile-generate
                 if let Some(value) = self.profile_generate {
                     push_if_supported(format!("-fprofile-generate={value}").into());
@@ -202,79 +285,8 @@ impl<'this> RustcCodegenFlags<'this> {
                 if let Some(value) = self.profile_use {
                     push_if_supported(format!("-fprofile-use={value}").into());
                 }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mguard
-                if let Some(value) = self.control_flow_guard {
-                    let cc_val = match value {
-                        "y" | "yes" | "on" | "true" | "checks" => Some("cf"),
-                        "nochecks" => Some("cf-nochecks"),
-                        "n" | "no" | "off" | "false" => Some("none"),
-                        _ => None,
-                    };
-                    if let Some(cc_val) = cc_val {
-                        push_if_supported(format!("-mguard={cc_val}").into());
-                    }
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-flto
-                if let Some(value) = self.lto {
-                    let cc_val = match value {
-                        "y" | "yes" | "on" | "true" | "fat" => Some("full"),
-                        "thin" => Some("thin"),
-                        _ => None,
-                    };
-                    if let Some(cc_val) = cc_val {
-                        push_if_supported(format!("-flto={cc_val}").into());
-                    }
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fPIC
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fPIE
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mdynamic-no-pic
-                if let Some(value) = self.relocation_model {
-                    let cc_flag = match value {
-                        "pic" => Some("-fPIC"),
-                        "pie" => Some("-fPIE"),
-                        "dynamic-no-pic" => Some("-mdynamic-no-pic"),
-                        _ => None,
-                    };
-                    if let Some(cc_flag) = cc_flag {
-                        push_if_supported(cc_flag.into());
-                    }
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fembed-bitcode
-                if let Some(value) = self.embed_bitcode {
-                    let cc_val = if value { "all" } else { "off" };
-                    push_if_supported(format!("-fembed-bitcode={cc_val}").into());
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fno-omit-frame-pointer
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-fomit-frame-pointer
-                if let Some(value) = self.force_frame_pointers {
-                    let cc_flag = if value {
-                        "-fno-omit-frame-pointer"
-                    } else {
-                        "-fomit-frame-pointer"
-                    };
-                    push_if_supported(cc_flag.into());
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-dead_strip
-                if let Some(false) = self.link_dead_code {
-                    push_if_supported("-dead_strip".into());
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mno-red-zone
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mred-zone
-                if let Some(value) = self.no_redzone {
-                    let cc_flag = if value { "-mno-red-zone" } else { "-mred-zone" };
-                    push_if_supported(cc_flag.into());
-                }
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-msoft-float
-                // https://clang.llvm.org/docs/ClangCommandLineReference.html#cmdoption-clang-mno-soft-float
-                if let Some(value) = self.soft_float {
-                    let cc_flag = if value {
-                        "-msoft-float"
-                    } else {
-                        "-mno-soft-float"
-                    };
-                    push_if_supported(cc_flag.into());
-                }
             }
+            ToolFamily::Gnu { .. } => {}
             ToolFamily::Msvc { .. } => {
                 // https://learn.microsoft.com/en-us/cpp/build/reference/guard-enable-control-flow-guard
                 if let Some(value) = self.control_flow_guard {