Support using sample profiles with partial debug info (driver)

Summary:
When using a profile, we used to require the use -gmlt so that we could
get access to the line locations. This is used to match line numbers in
the input profile to the line numbers in the function's IR.

But this is actually not necessary. The driver can provide source
location tracking without the emission of debug information. In these
cases, the annotation 'llvm.dbg.cu' is missing from the IR, but the
actual line location annotations are still present.

This patch tells the driver to only emit source location tracking
when -fprofile-sample-use is present in the command line.

Reviewers: echristo, dblaikie

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D5888

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@220383 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 2 deletions

diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 2c4118c279..9bf14c791b 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -575,8 +575,14 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
     NeedLocTracking = true;
   }
 
-  // If the user requested one of the flags in the -Rpass family, make sure
-  // that the backend tracks source location information.
+  // If the user requested to use a sample profile for PGO, then the
+  // backend will need to track source location information so the profile
+  // can be incorporated into the IR.
+  if (!Opts.SampleProfileFile.empty())
+    NeedLocTracking = true;
+
+  // If the user requested a flag that requires source locations available in
+  // the backend, make sure that the backend tracks source location information.
   if (NeedLocTracking && Opts.getDebugInfo() == CodeGenOptions::NoDebugInfo)
     Opts.setDebugInfo(CodeGenOptions::LocTrackingOnly);