[llvm-bugs] [Bug 51077] New: clang uses a lot of memory when compiling new T[big number]

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=51077

            Bug ID: 51077
           Summary: clang uses a lot of memory when compiling new T[big
                    number]
           Product: clang
           Version: 11.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: mihail.dektyarow at gmail.com
                CC: htmldeveloper at gmail.com, llvm-bugs at lists.llvm.org,
                    neeilans at live.com, richard-llvm at metafoo.co.uk

Created attachment 25020
  --> https://bugs.llvm.org/attachment.cgi?id=25020&action=edit
clang stdout

Steps to reproduce:
1. Create file source.cpp with following content:
struct T {
    char x;
};

T* f() {
    return new T[100000000];
}

2. Run clang++ -v -c source.cpp -o source.o

Expected outcome:
clang creates object file without using too much memory
Actual outcome:
clang uses about 8GB of memory (and then on my machine is killed for OOM)
clang output attached.

This is easily reproducible on godbolt.org: clang 9 compiles this code just
fine, clang 10.0 or above reports out of memory https://godbolt.org/z/d9oej9a57

If we replace struct T with using T = char, everything works fine.
If we replace T[100000000] with T[10000000], clang uses about 1.6GB of memory
but compiles successfully.

On other machine, clang 12 compiles this file, but uses about 12GB of memory in
process.

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