[clang/DIVar] Emit the flag for params that have unmodified value

Emit the debug info flag that indicates that a parameter has unchanged
value throughout a function.

([5/13] Introduce the debug entry values.)

Co-authored-by: Ananth Sowda <asowda@cisco.com>
Co-authored-by: Nikola Prica <nikola.prica@rt-rk.com>
Co-authored-by: Ivan Baev <ibaev@cisco.com>

Differential Revision: https://reviews.llvm.org/D58035

llvm-svn: 364424

1 files changed, 39 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index fce0902f34d..e8a6762d2b8 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -18,6 +18,7 @@
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "ConstantEmitter.h"
+#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclObjC.h"
@@ -3588,6 +3589,12 @@ void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, SourceLocation Loc,
   if (HasDecl && isa<FunctionDecl>(D))
     DeclCache[D->getCanonicalDecl()].reset(SP);
 
+  // We use the SPDefCache only in the case when the debug entry values option
+  // is set, in order to speed up parameters modification analysis.
+  if (CGM.getCodeGenOpts().EnableDebugEntryValues && HasDecl &&
+      isa<FunctionDecl>(D))
+    SPDefCache[cast<FunctionDecl>(D)].reset(SP);
+
   if (CGM.getCodeGenOpts().DwarfVersion >= 5) {
     // Starting with DWARF V5 method declarations are emitted as children of
     // the interface type.
@@ -3964,6 +3971,11 @@ llvm::DILocalVariable *CGDebugInfo::EmitDeclare(const VarDecl *VD,
                          llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
                          Builder.GetInsertBlock());
 
+  if (CGM.getCodeGenOpts().EnableDebugEntryValues && ArgNo) {
+    if (auto *PD = dyn_cast<ParmVarDecl>(VD))
+      ParamCache[PD].reset(D);
+  }
+
   return D;
 }
 
@@ -4555,6 +4567,29 @@ void CGDebugInfo::setDwoId(uint64_t Signature) {
   TheCU->setDWOId(Signature);
 }
 
+/// Analyzes each function parameter to determine whether it is constant
+/// throughout the function body.
+static void analyzeParametersModification(
+    ASTContext &Ctx,
+    llvm::DenseMap<const FunctionDecl *, llvm::TrackingMDRef> &SPDefCache,
+    llvm::DenseMap<const ParmVarDecl *, llvm::TrackingMDRef> &ParamCache) {
+  for (auto &SP : SPDefCache) {
+    auto *FD = SP.first;
+    assert(FD->hasBody() && "Functions must have body here");
+    const Stmt *FuncBody = (*FD).getBody();
+    for (auto Parm : FD->parameters()) {
+      ExprMutationAnalyzer FuncAnalyzer(*FuncBody, Ctx);
+      if (FuncAnalyzer.isMutated(Parm))
+        continue;
+
+      auto I = ParamCache.find(Parm);
+      assert(I != ParamCache.end() && "Parameters should be already cached");
+      auto *DIParm = cast<llvm::DILocalVariable>(I->second);
+      DIParm->setIsNotModified();
+    }
+  }
+}
+
 void CGDebugInfo::finalize() {
   // Creating types might create further types - invalidating the current
   // element and the size(), so don't cache/reference them.
@@ -4627,6 +4662,10 @@ void CGDebugInfo::finalize() {
     if (auto MD = TypeCache[RT])
       DBuilder.retainType(cast<llvm::DIType>(MD));
 
+  if (CGM.getCodeGenOpts().EnableDebugEntryValues)
+    // This will be used to emit debug entry values.
+    analyzeParametersModification(CGM.getContext(), SPDefCache, ParamCache);
+
   DBuilder.finalize();
 }