[PATCH] D29915: emit constant expression for new expression array size if it is one

[Nick Lewycky via Phabricator via cfe-commits]

nlewycky created this revision.

When the new expr's array size is an ICE, emit it as a constant expression.

This bypasses integer sanitization checks which are redundant on the expression since it's been checked by Sema. Fixes a clang codegen assertion on "void test() { new int[0+1]{0}; }" when building with -fsanitize=signed-integer-overflow.


https://reviews.llvm.org/D29915

Files:
  lib/CodeGen/CGExprCXX.cpp
  test/CodeGenCXX/new-array-init.cpp


Index: test/CodeGenCXX/new-array-init.cpp
===================================================================
--- test/CodeGenCXX/new-array-init.cpp
+++ test/CodeGenCXX/new-array-init.cpp
@@ -1,4 +1,5 @@
 // RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown %s -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown %s -emit-llvm -fsanitize=signed-integer-overflow -o - | FileCheck --check-prefix=SIO %s
 
 // CHECK: @[[ABC4:.*]] = {{.*}} constant [4 x i8] c"abc\00"
 // CHECK: @[[ABC15:.*]] = {{.*}} constant [15 x i8] c"abc\00\00\00\00
@@ -116,3 +117,9 @@
   struct Aggr { int a, b; };
   new Aggr[n] { 1, 2, 3 };
 }
+
+// SIO-LABEL: define void @_Z14constexpr_testv
+void constexpr_test() {
+  // SIO: call i8* @_Zna{{.}}(i32 4)
+  new int[0+1]{0};
+}
Index: lib/CodeGen/CGExprCXX.cpp
===================================================================
--- lib/CodeGen/CGExprCXX.cpp
+++ lib/CodeGen/CGExprCXX.cpp
@@ -659,7 +659,10 @@
   // Emit the array size expression.
   // We multiply the size of all dimensions for NumElements.
   // e.g for 'int[2][3]', ElemType is 'int' and NumElements is 6.
-  numElements = CGF.EmitScalarExpr(e->getArraySize());
+  numElements = CGF.CGM.EmitConstantExpr(e->getArraySize(),
+                                         CGF.getContext().getSizeType(), &CGF);
+  if (!numElements)
+    numElements = CGF.EmitScalarExpr(e->getArraySize());
   assert(isa<llvm::IntegerType>(numElements->getType()));
 
   // The number of elements can be have an arbitrary integer type;


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