[LV][BUG] Tiny fix for printing debug locations for absolute paths.

[zinovy.nis]

Summary

If a loop was defined in a file referenced by an absolute path (for ex. STL header from the system dir), then DEBUG print would print module dir and then that absolute path, which is wrong.

LV: Checking a loop in "Foo" from /home/myhome//usr/lib/gcc/z42_128-greencap-linux/1.2.3/../../../../include/c++/9.8.7/bits/list.tcc:171

The correct behavior is to just print the absolute path and skip module dir.

LV: Checking a loop in "Foo" from /usr/lib/gcc/z42_128-greencap-linux/1.2.3/../../../../include/c++/9.8.7/bits/list.tcc:171

[echristo]

Seems reasonable.

[zinovy.nis]

1. Slightly refactored to get rid of ugly format<..> calls.
2. Use path::append instead of string concatenation.

[nadav]

Zinovy,

Why is getDebugLocString defined in LoopVectorize.cpp? I am expecting other passes to also need this utility. Please refactor this function and put this function in a place where other passes would be able to use it.

Nadav

[yaron.keren]

If factored out as a function accepting a DebugLoc rather than an llvm::Instruction, it may be mergable with most of printDebugLoc from lib/CodeGen/MachineInstr.cpp. The print format is not identical but I'm not sure if this is a problem.

[zinovy.nis]

Thanks to Nadav and Yaron I refactored the code and significantly simplified it compared to my first patch. Also I added method 'print" to DebugLoc class which does the job.

Please re-review my new patch.

[nadav]

LGTM.

[echristo]

One small nit, otherwise LGTM.

-eric

lib/IR/DebugLoc.cpp

170 ↗

(On Diff #9106)

Formatting looks wrong here.

[zinovy.nis]

Nadav, Eric thanks!

lib/Transforms/Vectorize/LoopVectorize.cpp

 #include "llvm/IR/Value.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/BranchProbability.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Format.h"
+#include "llvm/Support/Path.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetLibraryInfo.h"
 #include "llvm/Transforms/Scalar.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
 #include "llvm/Transforms/Utils/VectorUtils.h"
 #include <algorithm>
 #include <map>
getDebugLocString(const Instruction *I) {
   if (!N) {
     const StringRef ModuleName =
         I->getParent()->getParent()->getParent()->getModuleIdentifier();
     return format<const char *, const char *, unsigned>("%s", ModuleName.data(),
                                                         "", 0U);
   }
   const DILocation Loc(N);
   const unsigned LineNo = Loc.getLineNumber();
-  const char *DirName = Loc.getDirectory().data();
   const char *FileName = Loc.getFilename().data();
+  // Absolute path doesn't need DirName.
+  if (sys::path::is_absolute(FileName))
+    return format<const char *, const char *, unsigned>("%s%s:%u", "", FileName,
+                                                        LineNo);
+  const char *DirName = Loc.getDirectory().data();
   return format("%s/%s:%u", DirName, FileName, LineNo);
 }
 #endif
 
 /// LoopVectorizationLegality checks if it is legal to vectorize a loop, and
 /// to what vectorization factor.
 /// This class does not look at the profitability of vectorization, only the
 /// legality. This class has two main kinds of checks: