[gcov] Add spanning tree optimization

gcov is an "Edge Profiling with Edge Counters" application according to Optimally Profiling and Tracing Programs (1994). The minimum number of counters necessary is |E|-(|V|-1). The unmeasured edges form a spanning tree. Both GCC --coverage and clang -fprofile-generate leverage this optimization. This patch implements the optimization for clang --coverage. The produced .gcda files are much smaller now.
llvm · Sep 13, 2020 · 63182c2 · 63182c2
1 parent f086e85
commit 63182c2
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Showing 6 changed files with 326 additions and 151 deletions.
diff --git a/clang/test/CodeGen/code-coverage-tsan.c b/clang/test/CodeGen/code-coverage-tsan.c
@@ -5,7 +5,6 @@
 // CHECK-LABEL: void @foo()
 /// Two counters are incremented by __tsan_atomic64_fetch_add.
 // CHECK:         call i64 @__tsan_atomic64_fetch_add
-// CHECK-NEXT:    call i64 @__tsan_atomic64_fetch_add
 // CHECK-NEXT:    call i32 @__tsan_atomic32_fetch_sub
 
 _Atomic(int) cnt;

diff --git a/compiler-rt/test/profile/Posix/gcov-fork.c b/compiler-rt/test/profile/Posix/gcov-fork.c
@@ -17,7 +17,7 @@ int main(void) {                   // CHECK-NEXT: 1: [[#@LINE]]:
   int status;                      // CHECK-NEXT: -: [[#@LINE]]:
   func1();                         // CHECK-NEXT: 1: [[#@LINE]]:
   pid_t pid = fork();              // CHECK-NEXT: 1: [[#@LINE]]:
-  if (pid == -1) return 1;         // CHECK-NEXT: 2: [[#@LINE]]:
+  if (pid == -1) return 1;         // CHECK-NEXT: 1: [[#@LINE]]:
   if (pid)                         // CHECK-NEXT: 2: [[#@LINE]]:
     wait(&status);                 // CHECK-NEXT: 1: [[#@LINE]]:
   func2();                         // CHECK-NEXT: 2: [[#@LINE]]:

diff --git a/compiler-rt/test/profile/gcov-dump-and-remove.c b/compiler-rt/test/profile/gcov-dump-and-remove.c
@@ -11,10 +11,10 @@
 extern void __gcov_dump(void);
 extern void __gcov_reset(void);
 extern int remove(const char *);   // CHECK:          -: [[#@LINE]]:extern int remove
-int main(void) {                   // CHECK-NEXT: #####: [[#@LINE]]:
-  __gcov_dump();                   // CHECK-NEXT: #####: [[#@LINE]]:
-  __gcov_reset();                  // CHECK-NEXT: #####: [[#@LINE]]:
-  if (remove("gcov-dump-and-remove.gcda") != 0) // CHECK-NEXT: #####: [[#@LINE]]:
+int main(void) {                   // CHECK-NEXT:     1: [[#@LINE]]:
+  __gcov_dump();                   // CHECK-NEXT:     1: [[#@LINE]]:
+  __gcov_reset();                  // CHECK-NEXT:     1: [[#@LINE]]:
+  if (remove("gcov-dump-and-remove.gcda") != 0) // CHECK-NEXT:     1: [[#@LINE]]:
     return 1;                      // CHECK-NEXT: #####: [[#@LINE]]: return 1;
                                    // CHECK-NEXT:     -: [[#@LINE]]:
   __gcov_dump();                   // CHECK-NEXT:     1: [[#@LINE]]: