[codegen] Fix crash in codegen caused by pointer calculation overflow

clang/lib/CodeGen/CGExprScalar.cpp

@@ -5831,10 +5831,15 @@ CodeGenFunction::EmitCheckedInBoundsGEP(llvm::Type *ElemTy, Value *Ptr,
   GEPOffsetAndOverflow EvaluatedGEP =
       EmitGEPOffsetInBytes(Ptr, GEPVal, getLLVMContext(), CGM, Builder);
 
-  assert((!isa<llvm::Constant>(EvaluatedGEP.TotalOffset) ||
-          EvaluatedGEP.OffsetOverflows == Builder.getFalse()) &&
-         "If the offset got constant-folded, we don't expect that there was an "
-         "overflow.");
+  if (!(!isa<llvm::Constant>(EvaluatedGEP.TotalOffset) ||
+        EvaluatedGEP.OffsetOverflows == Builder.getFalse())) {
+    DiagnosticsEngine &Diags = CGM.getDiags();
+    unsigned DiagID = Diags.getCustomDiagID(
+        DiagnosticsEngine::Error, "Expression caused pointer calculation "
+                                  "overflow during code generation");
+    Diags.Report(Loc, DiagID);
+    return GEPVal;
+  }
 
   auto *Zero = llvm::ConstantInt::getNullValue(IntPtrTy);
 

clang/test/CodeGen/ubsan-emit-bounds-check-crash-msp.c

@@ -0,0 +1,7 @@
+// REQUIRES: msp430-registered-target
+// RUN: %clang -c -fsanitize=undefined -Wno-tentative-definition-array -Wno-return-type -Wno-unused-value -Wno-array-bounds -Xclang -verify --target=msp430-- %s
+int a;
+_Complex double b[1][1];
+void c(void) {
+  b[a][8920]; // expected-error {{Expression caused pointer calculation overflow during code generation}}
+}

clang/test/CodeGen/ubsan-emit-bounds-check-crash-x86.c

@@ -0,0 +1,7 @@
+// REQUIRES: x86-registered-target
+// RUN: %clang -c -Wno-tentative-definition-array -Wno-return-type -Wno-unused-value -Wno-array-bounds -Xclang -verify --target=x86_64-- -fsanitize=undefined %s 
+int **a[];
+int main() {
+  (*a)[3300220222222200000]; // expected-error {{Expression caused pointer calculation overflow during code generation}}
+  return 0;
+}