[PATCH] D44511: [MSan] Introduce ActualFnStart. NFC

[Alexander Potapenko via Phabricator via llvm-commits]

glider created this revision.
glider added reviewers: vitalybuka, dvyukov.
Herald added a subscriber: llvm-commits.

This is a step towards the upcoming KMSAN implementation patch.
KMSAN is going to prepend a special basic block containing tool-specific calls to each function. Because we still want to instrument the original entry block, we'll need to store it in ActualFnStart.
For MSan this will still be F.getEntryBlock(), whereas for KMSAN it'll contain the second BB.


Repository:
  rL LLVM

https://reviews.llvm.org/D44511

Files:
  lib/Transforms/Instrumentation/MemorySanitizer.cpp


Index: lib/Transforms/Instrumentation/MemorySanitizer.cpp
===================================================================
--- lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -715,6 +715,7 @@
   ValueMap<Value*, Value*> ShadowMap, OriginMap;
   std::unique_ptr<VarArgHelper> VAHelper;
   const TargetLibraryInfo *TLI;
+  BasicBlock *ActualFnStart;
 
   // The following flags disable parts of MSan instrumentation based on
   // blacklist contents and command-line options.
@@ -931,6 +932,7 @@
   /// \brief Add MemorySanitizer instrumentation to a function.
   bool runOnFunction() {
     MS.initializeCallbacks(*F.getParent());
+    ActualFnStart = &F.getEntryBlock();
 
     // In the presence of unreachable blocks, we may see Phi nodes with
     // incoming nodes from such blocks. Since InstVisitor skips unreachable
@@ -941,7 +943,7 @@
     // Iterate all BBs in depth-first order and create shadow instructions
     // for all instructions (where applicable).
     // For PHI nodes we create dummy shadow PHIs which will be finalized later.
-    for (BasicBlock *BB : depth_first(&F.getEntryBlock()))
+    for (BasicBlock *BB : depth_first(ActualFnStart))
       visit(*BB);
 
     // Finalize PHI nodes.
@@ -1213,7 +1215,7 @@
       if (*ShadowPtr)
         return *ShadowPtr;
       Function *F = A->getParent();
-      IRBuilder<> EntryIRB(F->getEntryBlock().getFirstNonPHI());
+      IRBuilder<> EntryIRB(ActualFnStart->getFirstNonPHI());
       unsigned ArgOffset = 0;
       const DataLayout &DL = F->getParent()->getDataLayout();
       for (auto &FArg : F->args()) {
@@ -3211,7 +3213,7 @@
     if (!VAStartInstrumentationList.empty()) {
       // If there is a va_start in this function, make a backup copy of
       // va_arg_tls somewhere in the function entry block.
-      IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
+      IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
       VAArgOverflowSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
       Value *CopySize =
         IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AMD64FpEndOffset),
@@ -3333,7 +3335,7 @@
   void finalizeInstrumentation() override {
     assert(!VAArgSize && !VAArgTLSCopy &&
            "finalizeInstrumentation called twice");
-    IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
+    IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
     VAArgSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
     Value *CopySize = IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, 0),
                                     VAArgSize);
@@ -3518,7 +3520,7 @@
     if (!VAStartInstrumentationList.empty()) {
       // If there is a va_start in this function, make a backup copy of
       // va_arg_tls somewhere in the function entry block.
-      IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
+      IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
       VAArgOverflowSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
       Value *CopySize =
         IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, AArch64VAEndOffset),
@@ -3754,7 +3756,7 @@
   void finalizeInstrumentation() override {
     assert(!VAArgSize && !VAArgTLSCopy &&
            "finalizeInstrumentation called twice");
-    IRBuilder<> IRB(F.getEntryBlock().getFirstNonPHI());
+    IRBuilder<> IRB(MSV.ActualFnStart->getFirstNonPHI());
     VAArgSize = IRB.CreateLoad(MS.VAArgOverflowSizeTLS);
     Value *CopySize = IRB.CreateAdd(ConstantInt::get(MS.IntptrTy, 0),
                                     VAArgSize);


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