[PATCH] D34789: Copy arguments passed by value into explicit allocas for ASan

[Evgenii Stepanov via Phabricator via llvm-commits]

eugenis added inline comments.


================
Comment at: lib/Transforms/Instrumentation/AddressSanitizer.cpp:2544
+  Instruction *InsBefore = dyn_cast<Instruction>(FirstBB.getFirstInsertionPt());
+  IRBuilder<> IRB(InsBefore);
+  for (Argument &Arg : F.args()) {
----------------
You can avoid the cast by using this constructor: http://llvm-cs.pcc.me.uk/include/llvm/IR/IRBuilder.h#703

IRBuilder(BB, BB.getFirstInsertionPt());


================
Comment at: lib/Transforms/Instrumentation/AddressSanitizer.cpp:2551
+      AllocaInst *AI =
+          IRB.CreateAlloca(Ty, nullptr, Twine(Arg.getName()) + ".byval");
+      AI->setAlignment(Align);
----------------
Check what happens if the arg has no name. AFAIK it can be referenced as %0 (%1, etc) in the function body in that case, but getName() would return nullptr.


================
Comment at: lib/Transforms/Instrumentation/AddressSanitizer.cpp:2557
+      uint64_t AllocSize = M->getDataLayout().getTypeAllocSize(Ty);
+      IRB.CreateMemCpy(AI, &Arg, AllocSize, Align);
+    }
----------------
Check what happens when byval argument has not explicit align attribute.
AFAIK, it must be handled this way:
            unsigned ArgAlign = FArg.getParamAlignment();
            if (ArgAlign == 0) {
              Type *EltType = A->getType()->getPointerElementType();
              ArgAlign = DL.getABITypeAlignment(EltType);
            }



https://reviews.llvm.org/D34789