11d3074267
Use the llvm flag `-pgo-function-entry-coverage` to create single byte "counters" to track functions coverage. This mode has significantly less size overhead in both code and data because * We mark a function as "covered" with a store instead of an increment which generally requires fewer assembly instructions * We use a single byte per function rather than 8 bytes per block The trade off of course is that this mode only tells you if a function has been covered. This is useful, for example, to detect dead code. When combined with debug info correlation [0] we are able to create an instrumented Clang binary that is only 150M (the vanilla Clang binary is 143M). That is an overhead of 7M (4.9%) compared to the default instrumentation (without value profiling) which has an overhead of 31M (21.7%). [0] https://groups.google.com/g/llvm-dev/c/r03Z6JoN7d4 Reviewed By: kyulee Differential Revision: https://reviews.llvm.org/D116180
19 lines
530 B
C
19 lines
530 B
C
// RUN: %clang_pgogen -mllvm -pgo-function-entry-coverage %s -o %t.out
|
|
// RUN: env LLVM_PROFILE_FILE=%t.profraw %run %t.out
|
|
// RUN: llvm-profdata merge -o %t.profdata %t.profraw
|
|
// RUN: llvm-profdata show --covered %t.profdata | FileCheck %s --check-prefix CHECK --implicit-check-not goo
|
|
|
|
int foo(int i) { return 4 * i + 1; }
|
|
int bar(int i) { return 4 * i + 2; }
|
|
int goo(int i) { return 4 * i + 3; }
|
|
|
|
int main(int argc, char *argv[]) {
|
|
foo(5);
|
|
argc ? bar(6) : goo(7);
|
|
return 0;
|
|
}
|
|
|
|
// CHECK: main
|
|
// CHECK: foo
|
|
// CHECK: bar
|