[clang] 6d09aae - Revert "[clang] Add early exit when checking for const init of arrays."

[Adam Czachorowski via cfe-commits]

Author: Adam Czachorowski
Date: 2021-11-10T20:59:35+01:00
New Revision: 6d09aaecdfe51e13fc64d539aa7c9a790de341d7

URL: https://github.com/llvm/llvm-project/commit/6d09aaecdfe51e13fc64d539aa7c9a790de341d7
DIFF: https://github.com/llvm/llvm-project/commit/6d09aaecdfe51e13fc64d539aa7c9a790de341d7.diff

LOG: Revert "[clang] Add early exit when checking for const init of arrays."

This reverts commit 48bb5f4cbe8d5951c1153e469dc6713a122b7fa3.

Several breakages, including ARM (fixed later, but not sufficient) and
MSan (to be diagnosed later).

Differential Revision: https://reviews.llvm.org/D113599

Added: 
    

Modified: 
    clang/lib/AST/ExprConstant.cpp

Removed: 
    clang/test/SemaCXX/PR51712-large-array-constexpr-check-oom.cpp


################################################################################
diff  --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index a6da3d3fbea2d..fe96db9ca918e 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -10596,55 +10596,28 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
   bool HadZeroInit = Value->hasValue();
 
   if (const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(Type)) {
-    unsigned FinalSize = CAT->getSize().getZExtValue();
+    unsigned N = CAT->getSize().getZExtValue();
 
     // Preserve the array filler if we had prior zero-initialization.
     APValue Filler =
       HadZeroInit && Value->hasArrayFiller() ? Value->getArrayFiller()
                                              : APValue();
 
-    *Value = APValue(APValue::UninitArray(), 0, FinalSize);
-    if (FinalSize == 0)
-      return true;
+    *Value = APValue(APValue::UninitArray(), N, N);
+
+    if (HadZeroInit)
+      for (unsigned I = 0; I != N; ++I)
+        Value->getArrayInitializedElt(I) = Filler;
 
+    // Initialize the elements.
     LValue ArrayElt = Subobject;
     ArrayElt.addArray(Info, E, CAT);
-    // We do the whole initialization in two passes, first for just one element,
-    // then for the whole array. It's possible we may find out we can't do const
-    // init in the first pass, in which case we avoid allocating a potentially
-    // large array. We don't do more passes because expanding array requires
-    // copying the data, which is wasteful.
-    for (const unsigned N : {1u, FinalSize}) {
-      unsigned OldElts = Value->getArrayInitializedElts();
-      if (OldElts == N)
-        break;
-
-      // Expand the array to appropriate size.
-      APValue NewValue(APValue::UninitArray(), N, FinalSize);
-      for (unsigned I = 0; I < OldElts; ++I)
-        NewValue.getArrayInitializedElt(I).swap(
-            Value->getArrayInitializedElt(I));
-      Value->swap(NewValue);
-
-      if (HadZeroInit)
-        for (unsigned I = OldElts; I < N; ++I)
-          Value->getArrayInitializedElt(I) = Filler;
-
-      // Initialize the elements.
-      for (unsigned I = OldElts; I < N; ++I) {
-        if (!VisitCXXConstructExpr(E, ArrayElt,
-                                   &Value->getArrayInitializedElt(I),
-                                   CAT->getElementType()) ||
-            !HandleLValueArrayAdjustment(Info, E, ArrayElt,
-                                         CAT->getElementType(), 1))
-          return false;
-        // When checking for const initilization any diagnostic is considered
-        // an error.
-        if (Info.EvalStatus.Diag && !Info.EvalStatus.Diag->empty() &&
-            !Info.keepEvaluatingAfterFailure())
-          return false;
-      }
-    }
+    for (unsigned I = 0; I != N; ++I)
+      if (!VisitCXXConstructExpr(E, ArrayElt, &Value->getArrayInitializedElt(I),
+                                 CAT->getElementType()) ||
+          !HandleLValueArrayAdjustment(Info, E, ArrayElt, CAT->getElementType(),
+                                       1))
+        return false;
 
     return true;
   }

diff  --git a/clang/test/SemaCXX/PR51712-large-array-constexpr-check-oom.cpp b/clang/test/SemaCXX/PR51712-large-array-constexpr-check-oom.cpp
deleted file mode 100644
index 1bbc1b5c863c0..0000000000000
--- a/clang/test/SemaCXX/PR51712-large-array-constexpr-check-oom.cpp
+++ /dev/null
@@ -1,11 +0,0 @@
-// REQUIRES: shell
-// UNSUPPORTED: win32
-// RUN: ulimit -v 1048576
-// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify -triple=x86_64 %s
-// expected-no-diagnostics
-
-// This used to require too much memory and crash with OOM.
-struct {
-  int a, b, c, d;
-} arr[1<<30];
-