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3 files changed, 94 insertions, 78 deletions

diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index c45d637177e..085935b94df 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -549,7 +549,11 @@ pub(crate) unsafe fn optimize(
                     continue;
                 }
                 if pass_name == "insert-gcov-profiling" || pass_name == "instrprof" {
-                    // Instrumentation should be inserted before optimization.
+                    // Instrumentation must be inserted before optimization,
+                    // otherwise LLVM may optimize some functions away which
+                    // breaks llvm-cov.
+                    //
+                    // This mirrors what Clang does in lib/CodeGen/BackendUtil.cpp.
                     llvm::LLVMRustAddPass(mpm, find_pass(pass_name).unwrap());
                     continue;
                 }
diff --git a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_inline_crate.txt b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_inline_crate.txt
index c38d2f87ace..cc98956e307 100644
--- a/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_inline_crate.txt
+++ b/src/test/run-make-fulldeps/coverage-reports/expected_show_coverage.uses_inline_crate.txt
@@ -31,103 +31,109 @@
    29|      1|    use_this_lib_crate();
    30|      1|}
    31|       |
-   32|       |#[inline(always)]
-   33|      2|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
-   34|      2|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
-   35|      2|}
+   32|       |
+   33|       |
+   34|       |
+   35|       |
+   36|       |
+   37|       |
+   38|       |#[inline(always)]
+   39|      2|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
+   40|      2|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
+   41|      2|}
   ------------------
   | used_inline_crate::used_only_from_bin_crate_generic_function::<&alloc::vec::Vec<i32>>:
-  |   33|      1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
-  |   34|      1|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
-  |   35|      1|}
+  |   39|      1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
+  |   40|      1|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
+  |   41|      1|}
   ------------------
   | used_inline_crate::used_only_from_bin_crate_generic_function::<&str>:
-  |   33|      1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
-  |   34|      1|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
-  |   35|      1|}
+  |   39|      1|pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
+  |   40|      1|    println!("used_only_from_bin_crate_generic_function with {:?}", arg);
+  |   41|      1|}
   ------------------
   | Unexecuted instantiation: used_inline_crate::used_only_from_bin_crate_generic_function::<_>
   ------------------
-   36|       |// Expect for above function: `Unexecuted instantiation` (see notes in `used_crate.rs`)
-   37|       |
-   38|       |#[inline(always)]
-   39|      4|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
-   40|      4|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
-   41|      4|}
+   42|       |// Expect for above function: `Unexecuted instantiation` (see notes in `used_crate.rs`)
+   43|       |
+   44|       |#[inline(always)]
+   45|      4|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
+   46|      4|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
+   47|      4|}
   ------------------
   | used_inline_crate::used_only_from_this_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
-  |   39|      2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   40|      2|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
-  |   41|      2|}
+  |   45|      2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   46|      2|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
+  |   47|      2|}
   ------------------
   | used_inline_crate::used_only_from_this_lib_crate_generic_function::<&str>:
-  |   39|      2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   40|      2|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
-  |   41|      2|}
+  |   45|      2|pub fn used_only_from_this_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   46|      2|    println!("used_only_from_this_lib_crate_generic_function with {:?}", arg);
+  |   47|      2|}
   ------------------
-   42|       |
-   43|       |#[inline(always)]
-   44|      3|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-   45|      3|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-   46|      3|}
+   48|       |
+   49|       |#[inline(always)]
+   50|      3|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+   51|      3|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+   52|      3|}
   ------------------
   | used_inline_crate::used_from_bin_crate_and_lib_crate_generic_function::<alloc::vec::Vec<i32>>:
-  |   44|      1|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   45|      1|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-  |   46|      1|}
+  |   50|      1|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   51|      1|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+  |   52|      1|}
   ------------------
   | used_inline_crate::used_from_bin_crate_and_lib_crate_generic_function::<&str>:
-  |   44|      2|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   45|      2|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-  |   46|      2|}
+  |   50|      2|pub fn used_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   51|      2|    println!("used_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+  |   52|      2|}
   ------------------
-   47|       |
-   48|       |#[inline(always)]
-   49|      3|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-   50|      3|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-   51|      3|}
+   53|       |
+   54|       |#[inline(always)]
+   55|      3|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+   56|      3|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+   57|      3|}
   ------------------
   | used_inline_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>:
-  |   49|      1|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   50|      1|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-  |   51|      1|}
+  |   55|      1|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   56|      1|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+  |   57|      1|}
   ------------------
   | used_inline_crate::used_with_same_type_from_bin_crate_and_lib_crate_generic_function::<&str>:
-  |   49|      2|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
-  |   50|      2|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
-  |   51|      2|}
+  |   55|      2|pub fn used_with_same_type_from_bin_crate_and_lib_crate_generic_function<T: Debug>(arg: T) {
+  |   56|      2|    println!("used_with_same_type_from_bin_crate_and_lib_crate_generic_function with {:?}", arg);
+  |   57|      2|}
   ------------------
-   52|       |
-   53|       |#[inline(always)]
-   54|      0|pub fn unused_generic_function<T: Debug>(arg: T) {
-   55|      0|    println!("unused_generic_function with {:?}", arg);
-   56|      0|}
-   57|       |
-   58|       |#[inline(always)]
-   59|      0|pub fn unused_function() {
-   60|      0|    let is_true = std::env::args().len() == 1;
-   61|      0|    let mut countdown = 2;
-   62|      0|    if !is_true {
-   63|      0|        countdown = 20;
-   64|      0|    }
-   65|      0|}
-   66|       |
-   67|       |#[inline(always)]
-   68|      0|fn unused_private_function() {
-   69|      0|    let is_true = std::env::args().len() == 1;
-   70|      0|    let mut countdown = 2;
-   71|      0|    if !is_true {
-   72|      0|        countdown = 20;
-   73|      0|    }
-   74|      0|}
-   75|       |
-   76|      2|fn use_this_lib_crate() {
-   77|      2|    used_from_bin_crate_and_lib_crate_generic_function("used from library used_crate.rs");
-   78|      2|    used_with_same_type_from_bin_crate_and_lib_crate_generic_function(
-   79|      2|        "used from library used_crate.rs",
-   80|      2|    );
-   81|      2|    let some_vec = vec![5, 6, 7, 8];
-   82|      2|    used_only_from_this_lib_crate_generic_function(some_vec);
-   83|      2|    used_only_from_this_lib_crate_generic_function("used ONLY from library used_crate.rs");
-   84|      2|}
+   58|       |
+   59|       |#[inline(always)]
+   60|      0|pub fn unused_generic_function<T: Debug>(arg: T) {
+   61|      0|    println!("unused_generic_function with {:?}", arg);
+   62|      0|}
+   63|       |
+   64|       |#[inline(always)]
+   65|      0|pub fn unused_function() {
+   66|      0|    let is_true = std::env::args().len() == 1;
+   67|      0|    let mut countdown = 2;
+   68|      0|    if !is_true {
+   69|      0|        countdown = 20;
+   70|      0|    }
+   71|      0|}
+   72|       |
+   73|       |#[inline(always)]
+   74|      0|fn unused_private_function() {
+   75|      0|    let is_true = std::env::args().len() == 1;
+   76|      0|    let mut countdown = 2;
+   77|      0|    if !is_true {
+   78|      0|        countdown = 20;
+   79|      0|    }
+   80|      0|}
+   81|       |
+   82|      2|fn use_this_lib_crate() {
+   83|      2|    used_from_bin_crate_and_lib_crate_generic_function("used from library used_crate.rs");
+   84|      2|    used_with_same_type_from_bin_crate_and_lib_crate_generic_function(
+   85|      2|        "used from library used_crate.rs",
+   86|      2|    );
+   87|      2|    let some_vec = vec![5, 6, 7, 8];
+   88|      2|    used_only_from_this_lib_crate_generic_function(some_vec);
+   89|      2|    used_only_from_this_lib_crate_generic_function("used ONLY from library used_crate.rs");
+   90|      2|}
 
diff --git a/src/test/run-make-fulldeps/coverage/lib/used_inline_crate.rs b/src/test/run-make-fulldeps/coverage/lib/used_inline_crate.rs
index 249e99fccb8..4a052756d4e 100644
--- a/src/test/run-make-fulldeps/coverage/lib/used_inline_crate.rs
+++ b/src/test/run-make-fulldeps/coverage/lib/used_inline_crate.rs
@@ -29,6 +29,12 @@ pub fn used_inline_function() {
     use_this_lib_crate();
 }
 
+
+
+
+
+
+
 #[inline(always)]
 pub fn used_only_from_bin_crate_generic_function<T: Debug>(arg: T) {
     println!("used_only_from_bin_crate_generic_function with {:?}", arg);