Reland https://github.com/llvm/llvm-project/pull/133173
Clang spawns a new thread to avoid running out of stack space. This can
make debugging and performance analysis more difficult as how the
threads are connected is difficult to recover.
This patch introduces `runOnNewStack` and applies it in Clang. On
platforms that have good support for it this allocates a new stack and
moves to it using assembly. Doing split stacks like this actually runs
on most platforms, but many debuggers and unwinders reject the large or
backwards stack offsets that occur. Apple platforms and tools are known
to support this, so this only enables it there for now.
…thread to get more stack space (#133173)"
This change breaks the Clang build on Mac AArch64.
This reverts commit d0c973a7a0149db3b71767d4c5a20a31e6a8ed5b. This
reverts commit 429a84f8a4bf559f43f50072747ef49d3e3b2cf1. This reverts
commit 4f64c80d5a23c244f942193e58ecac666c173308.
Clang spawns a new thread to avoid running out of stack space. This can
make debugging and performance analysis more difficult as how the
threads are connected is difficult to recover.
This patch introduces `runOnNewStack` and applies it in Clang. On
platforms that have good support for it this allocates a new stack and
moves to it using assembly. Doing split stacks like this actually runs
on most platforms, but many debuggers and unwinders reject the large or
backwards stack offsets that occur. Apple platforms and tools are known
to support this, so this only enables it there for now.
Summary:
Clang performs various recursive operations (such as template instantiation),
and may use non-trivial amounts of stack space in each recursive step (for
instance, due to recursive AST walks). While we try to keep the stack space
used by such steps to a minimum and we have explicit limits on the number of
such steps we perform, it's impractical to guarantee that we won't blow out the
stack on deeply recursive template instantiations on complex ASTs, even with
only a moderately high instantiation depth limit.
The user experience in these cases is generally terrible: we crash with
no hint of what went wrong. Under this patch, we attempt to do better:
* Detect when the stack is nearly exhausted, and produce a warning with a
nice template instantiation backtrace, telling the user that we might
run slowly or crash.
* For cases where we're forced to trigger recursive template
instantiation in arbitrarily-deeply-nested contexts, check whether
we're nearly out of stack space and allocate a new stack (by spawning
a new thread) after producing the warning.
Reviewers: rnk, aaron.ballman
Subscribers: mgorny, cfe-commits
Tags: #clang
Differential Revision: https://reviews.llvm.org/D66361
llvm-svn: 369940
