[Driver] -ftime-trace: derive trace file names from -o and -dumpdir

Inspired by D133662.
Close https://github.com/llvm/llvm-project/issues/57285

When -ftime-trace is specified and the driver performs both compilation and
linking phases, the trace files are currently placed in the temporary directory
(/tmp by default on *NIX). A more sensible behavior would be to derive the trace
file names from the -o option, similar to how GCC derives auxiliary and dump
file names. Use -dumpdir (D149193) to implement the -gsplit-dwarf like behavior.

The following script demonstrates the time trace filenames.

```
#!/bin/sh -e
PATH=/tmp/Rel/bin:$PATH                # adapt according to your build directory
mkdir -p d e f
echo 'int main() {}' > d/a.c
echo > d/b.c

a() { rm $1 || exit 1; }

clang -ftime-trace d/a.c d/b.c         # previously /tmp/[ab]-*.json
a a-a.json; a a-b.json
clang -ftime-trace d/a.c d/b.c -o e/x  # previously /tmp/[ab]-*.json
a e/x-a.json; a e/x-b.json
clang -ftime-trace d/a.c d/b.c -o e/x -dumpdir f/
a f/a.json; a f/b.json
clang -ftime-trace=f d/a.c d/b.c -o e/x
a f/a-*.json; a f/b-*.json

clang -c -ftime-trace d/a.c d/b.c
a a.json b.json
clang -c -ftime-trace=f d/a.c d/b.c
a f/a.json f/b.json

clang -c -ftime-trace d/a.c -o e/xa.o
a e/xa.json
clang -c -ftime-trace d/a.c -o e/xa.o -dumpdir f/g
a f/ga.json
```

The driver checks `-ftime-trace` and `-ftime-trace=`, infers the trace file
name, and passes `-ftime-trace=` to cc1. The `-ftime-trace` cc1 option is
removed.

With offloading, previously `-ftime-trace` is passed to all offloading
actions, causing the same trace file to be overwritten by host and
offloading actions. This patch doesn't attempt to support offloading (D133662),
but makes a sensible change (`OffloadingPrefix.empty()`) to ensure we don't
overwrite the trace file.

Minor behavior differences: the trace file is now a result file, which
will be removed upon an error. -ftime-trace-granularity=0, like
-ftime-trace, can now cause a -Wunused-command-line-argument warning.

Reviewed By: Maetveis

Differential Revision: https://reviews.llvm.org/D150282

1 files changed, 33 insertions, 0 deletions

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index 879f3bf..535d9c9 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -5234,6 +5234,37 @@ InputInfoList Driver::BuildJobsForAction(
   return Result;
 }
 
+static void handleTimeTrace(Compilation &C, const ArgList &Args,
+                            const JobAction *JA, const char *BaseInput,
+                            const InputInfo &Result) {
+  Arg *A =
+      Args.getLastArg(options::OPT_ftime_trace, options::OPT_ftime_trace_EQ);
+  if (!A)
+    return;
+  SmallString<128> Path;
+  if (A->getOption().matches(options::OPT_ftime_trace_EQ)) {
+    Path = A->getValue();
+    if (llvm::sys::fs::is_directory(Path)) {
+      SmallString<128> Tmp(Result.getFilename());
+      llvm::sys::path::replace_extension(Tmp, "json");
+      llvm::sys::path::append(Path, llvm::sys::path::filename(Tmp));
+    }
+  } else {
+    if (Arg *DumpDir = Args.getLastArgNoClaim(options::OPT_dumpdir)) {
+      // The trace file is ${dumpdir}${basename}.json. Note that dumpdir may not
+      // end with a path separator.
+      Path = DumpDir->getValue();
+      Path += llvm::sys::path::filename(BaseInput);
+    } else {
+      Path = Result.getFilename();
+    }
+    llvm::sys::path::replace_extension(Path, "json");
+  }
+  const char *ResultFile = C.getArgs().MakeArgString(Path);
+  C.addTimeTraceFile(ResultFile, JA);
+  C.addResultFile(ResultFile, JA);
+}
+
 InputInfoList Driver::BuildJobsForActionNoCache(
     Compilation &C, const Action *A, const ToolChain *TC, StringRef BoundArch,
     bool AtTopLevel, bool MultipleArchs, const char *LinkingOutput,
@@ -5483,6 +5514,8 @@ InputInfoList Driver::BuildJobsForActionNoCache(
                                              AtTopLevel, MultipleArchs,
                                              OffloadingPrefix),
                        BaseInput);
+    if (T->canEmitIR() && OffloadingPrefix.empty())
+      handleTimeTrace(C, Args, JA, BaseInput, Result);
   }
 
   if (CCCPrintBindings && !CCGenDiagnostics) {