-ftime-report: reorganize timers

The code generation time is unclear in the -ftime-report output:

* The two clang timers "Code Generation Time" and "LLVM IR Generation
  Time" are in the default group "Miscellaneous Ungrouped Timers".
* There is also a "Clang front-end time" group, which actually includes
  code generation time.

```
===-------------------------------------------------------------------------===
                         Miscellaneous Ungrouped Timers
===-------------------------------------------------------------------------===

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   0.0611 (  1.7%)   0.0099 (  4.4%)   0.0710 (  1.9%)   0.0713 (  1.9%)  LLVM IR Generation Time
   3.5140 ( 98.3%)   0.2165 ( 95.6%)   3.7306 ( 98.1%)   3.7342 ( 98.1%)  Code Generation Time
   3.5751 (100.0%)   0.2265 (100.0%)   3.8016 (100.0%)   3.8055 (100.0%)  Total
...
===-------------------------------------------------------------------------===
                          Clang front-end time report
===-------------------------------------------------------------------------===
  Total Execution Time: 3.9108 seconds (3.9146 wall clock)

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   3.6802 (100.0%)   0.2306 (100.0%)   3.9108 (100.0%)   3.9146 (100.0%)  Clang front-end timer
   3.6802 (100.0%)   0.2306 (100.0%)   3.9108 (100.0%)   3.9146 (100.0%)  Total
```

This patch

* renames "Clang front-end time report" (FrontendAction time) to "Clang
  time report",
* renames "Clang front-end" to "Front end",
* moves "LLVM IR Generation" into the group,
* replaces "Code Generation time" with "Optimizer" (middle end) and
  "Machine code generation" (back end).

```
% clang -c sqlite3.i -w -ftime-report -mllvm -sort-timers=0
...
===-------------------------------------------------------------------------===
                               Clang time report
===-------------------------------------------------------------------------===
  Total Execution Time: 1.5922 seconds (1.5972 wall clock)

   ---User Time---   --System Time--   --User+System--   ---Wall Time---  --- Name ---
   0.5107 ( 35.9%)   0.0105 (  6.2%)   0.5211 ( 32.7%)   0.5222 ( 32.7%)  Front end
   0.2464 ( 17.3%)   0.0340 ( 20.0%)   0.2804 ( 17.6%)   0.2814 ( 17.6%)  LLVM IR generation
   0.6240 ( 43.9%)   0.1235 ( 72.7%)   0.7475 ( 47.0%)   0.7503 ( 47.0%)  Machine code generation
   0.0413 (  2.9%)   0.0018 (  1.0%)   0.0431 (  2.7%)   0.0433 (  2.7%)  Optimizer
   1.4224 (100.0%)   0.1698 (100.0%)   1.5922 (100.0%)   1.5972 (100.0%)  Total
```

Pull Request: https://github.com/llvm/llvm-project/pull/122225

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Support/Timer.cpp b/llvm/lib/Support/Timer.cpp
index 1fa2cdf..fbf3bec 100644
--- a/llvm/lib/Support/Timer.cpp
+++ b/llvm/lib/Support/Timer.cpp
@@ -166,6 +166,11 @@ void Timer::clear() {
   Time = StartTime = TimeRecord();
 }
 
+void Timer::yieldTo(Timer &O) {
+  stopTimer();
+  O.startTimer();
+}
+
 static void printVal(double Val, double Total, raw_ostream &OS) {
   if (Total < 1e-7)   // Avoid dividing by zero.
     OS << "        -----     ";