vendor/clang/clang-trunk-r300890

1 files changed, 28 insertions, 10 deletions

diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 265ef27a46b0..719147a58e08 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -533,6 +533,15 @@ bool CodeGenFunction::sanitizePerformTypeCheck() const {
          SanOpts.has(SanitizerKind::Vptr);
 }
 
+/// Check if a runtime null check for \p Ptr can be omitted.
+static bool canOmitPointerNullCheck(llvm::Value *Ptr) {
+  // Note: do not perform any constant-folding in this function. That is best
+  // left to the IR builder.
+
+  // Pointers to alloca'd memory are non-null.
+  return isa<llvm::AllocaInst>(Ptr->stripPointerCastsNoFollowAliases());
+}
+
 void CodeGenFunction::EmitTypeCheck(TypeCheckKind TCK, SourceLocation Loc,
                                     llvm::Value *Ptr, QualType Ty,
                                     CharUnits Alignment,
@@ -554,19 +563,28 @@ void CodeGenFunction::EmitTypeCheck(TypeCheckKind TCK, SourceLocation Loc,
   bool AllowNullPointers = TCK == TCK_DowncastPointer || TCK == TCK_Upcast ||
                            TCK == TCK_UpcastToVirtualBase;
   if ((SanOpts.has(SanitizerKind::Null) || AllowNullPointers) &&
-      !SkippedChecks.has(SanitizerKind::Null)) {
+      !SkippedChecks.has(SanitizerKind::Null) &&
+      !canOmitPointerNullCheck(Ptr)) {
     // The glvalue must not be an empty glvalue.
     llvm::Value *IsNonNull = Builder.CreateIsNotNull(Ptr);
 
-    if (AllowNullPointers) {
-      // When performing pointer casts, it's OK if the value is null.
-      // Skip the remaining checks in that case.
-      Done = createBasicBlock("null");
-      llvm::BasicBlock *Rest = createBasicBlock("not.null");
-      Builder.CreateCondBr(IsNonNull, Rest, Done);
-      EmitBlock(Rest);
-    } else {
-      Checks.push_back(std::make_pair(IsNonNull, SanitizerKind::Null));
+    // The IR builder can constant-fold the null check if the pointer points to
+    // a constant.
+    bool PtrIsNonNull =
+        IsNonNull == llvm::ConstantInt::getTrue(getLLVMContext());
+
+    // Skip the null check if the pointer is known to be non-null.
+    if (!PtrIsNonNull) {
+      if (AllowNullPointers) {
+        // When performing pointer casts, it's OK if the value is null.
+        // Skip the remaining checks in that case.
+        Done = createBasicBlock("null");
+        llvm::BasicBlock *Rest = createBasicBlock("not.null");
+        Builder.CreateCondBr(IsNonNull, Rest, Done);
+        EmitBlock(Rest);
+      } else {
+        Checks.push_back(std::make_pair(IsNonNull, SanitizerKind::Null));
+      }
     }
   }