Okay, how much ram does it take to build Rust?

Hey there folks,

I've got poudriere running on a recently-16-ified VM with 8 cores and 48G ram (up from 32), and to eat the dogfood I'm attempting to build all my own packages.

lang/rust is a big one.  It pontificates for about two hours, then dies with:

[ 45% 1690/3710] Building RISCVGenExegesis.inc...
[ 45% 1691/3710] Building RISCVGenGlobalISel.inc...
FAILED: [code=262] lib/Target/RISCV/RISCVGenGlobalISel.inc /wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build/lib/Target/RISCV/RISCVGenGlobalISel.inc 
cd /wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build && /wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build/bin/llvm-tblgen -gen-global-isel -I /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target/RISCV -I/wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build/include -I/wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/include -I /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target -no-warn-on-unused-template-args /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target/RISCV/RISCVGISel.td --write-if-changed -o lib/Target/RISCV/RISCVGenGlobalISel.inc -d lib/Target/RISCV/RISCVGenGlobalISel.inc.d
LLVM ERROR: out of memory
Allocation failed
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0. Program arguments: /wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build/bin/llvm-tblgen -gen-global-isel -I /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target/RISCV -I/wrkdirs/usr/ports/lang/rust/work/_build/x86_64-unknown-freebsd/llvm/build/include -I/wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/include -I /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target -no-warn-on-unused-template-args /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/src/llvm-project/llvm/lib/Target/RISCV/RISCVGISel.td --write-if-changed -o lib/Target/RISCV/RISCVGenGlobalISel.inc -d lib/Target/RISCV/RISCVGenGlobalISel.inc.d
ninja: build stopped: subcommand failed.

thread 'main' panicked at /wrkdirs/usr/ports/lang/rust/work/rustc-1.89.0-src/vendor/cmake-0.1.54/src/lib.rs:1119:5:

command did not execute successfully, got: exit status: 6

build script failed, must exit now
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: cmake::fail

Full logs here:

https://poudriere-src.isc.org/data/freebsd:16:x86:64-pkgbase-default_git/2025-09-11_04h17m42s/logs/rust-1.89.0.log

Is this actually likely an LLVM bug, or is 48G of ram not enough (it barely climbed at all for most of the files).  Note that I'm not doing anything multi-threaded with Poudriere, this is single CPU bound.

-Dan