[llvm] API for encoding/decoding DWARF discriminators.
Summary:
Added a pair of APIs for encoding/decoding the 3 components of a DWARF discriminator described in http://lists.llvm.org/pipermail/llvm-dev/2016-October/106532.html: the base discriminator, the duplication factor (useful in profile-guided optimization) and the copy index (used to identify copies of code in cases like loop unrolling)
The encoding packs 3 unsigned values in 32 bits. This CL addresses 2 issues:
- communicates overflow back to the user
- supports encoding all 3 components together. Current APIs assume a sequencing of events. For example, creating a new discriminator based on an existing one by changing the base discriminator was not supported.
Reviewers: davidxl, danielcdh, wmi, dblaikie
Reviewed By: dblaikie
Subscribers: zzheng, dmgreen, aprantl, JDevlieghere, llvm-commits
Differential Revision: https://reviews.llvm.org/D55681
llvm-svn: 349973
diff --git a/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp b/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
index 5653bab..fcb7402 100644
--- a/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
+++ b/llvm/lib/Target/X86/X86DiscriminateMemOps.cpp
@@ -21,6 +21,7 @@
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/ProfileData/SampleProf.h"
#include "llvm/ProfileData/SampleProfReader.h"
+#include "llvm/Support/Debug.h"
#include "llvm/Transforms/IPO/SampleProfile.h"
using namespace llvm;
@@ -107,27 +108,36 @@
if (!DI) {
DI = ReferenceDI;
}
- DenseSet<unsigned> &Set = Seen[diToLocation(DI)];
+ Location L = diToLocation(DI);
+ DenseSet<unsigned> &Set = Seen[L];
const std::pair<DenseSet<unsigned>::iterator, bool> TryInsert =
Set.insert(DI->getBaseDiscriminator());
if (!TryInsert.second) {
- DI = DI->setBaseDiscriminator(++MemOpDiscriminators[diToLocation(DI)]);
- updateDebugInfo(&MI, DI);
- Changed = true;
- const std::pair<DenseSet<unsigned>::iterator, bool> MustInsert =
- Set.insert(DI->getBaseDiscriminator());
- // FIXME (mtrofin): check if the to-be inserted base discriminator can
- // be added. This requires a new API on DILocation.
- // The assumption is that this scenario is infrequent/OK not to support.
- // If evidence points otherwise, we can explore synthesize unique DIs by
- // adding fake line numbers.
- if (!MustInsert.second) {
- LLVM_DEBUG(dbgs()
- << "Unable to create a unique discriminator in "
+ unsigned BF, DF, CI = 0;
+ DILocation::decodeDiscriminator(DI->getDiscriminator(), BF, DF, CI);
+ Optional<unsigned> EncodedDiscriminator = DILocation::encodeDiscriminator(
+ MemOpDiscriminators[L] + 1, DF, CI);
+
+ if (!EncodedDiscriminator) {
+ // FIXME(mtrofin): The assumption is that this scenario is infrequent/OK
+ // not to support. If evidence points otherwise, we can explore synthesizeing
+ // unique DIs by adding fake line numbers, or by constructing 64 bit
+ // discriminators.
+ LLVM_DEBUG(dbgs() << "Unable to create a unique discriminator "
+ "for instruction with memory operand in: "
<< DI->getFilename() << " Line: " << DI->getLine()
<< " Column: " << DI->getColumn()
- << ". This is likely due to a large macro expansion.\n");
+ << ". This is likely due to a large macro expansion. \n");
+ continue;
}
+ // Since we were able to encode, bump the MemOpDiscriminators.
+ ++MemOpDiscriminators[L];
+ DI = DI->cloneWithDiscriminator(EncodedDiscriminator.getValue());
+ updateDebugInfo(&MI, DI);
+ Changed = true;
+ std::pair<DenseSet<unsigned>::iterator, bool> MustInsert =
+ Set.insert(DI->getBaseDiscriminator());
+ assert(MustInsert.second && "New discriminator shouldn't be present in set");
}
// Bump the reference DI to avoid cramming discriminators on line 0.