[PATCH] D111105: [clang] Add option to clear AST memory before running LLVM passes

[David Blaikie via Phabricator via cfe-commits]

dblaikie accepted this revision.
dblaikie added a comment.
This revision is now accepted and ready to land.

In D111105#3043734 <https://reviews.llvm.org/D111105#3043734>, @aeubanks wrote:

> update test
> I checked to make sure that we're not accepting -clear-ast-before-backend as a driver flag

Ah, OK - sorry I mistested some things when I was thinking about that.



================
Comment at: clang/test/Misc/clear-ast-before-backend.c:2-3
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend %s -S
+// RUN: %clang -target x86_64-linux-gnu -c -Xclang -clear-ast-before-backend %s -S -### 2>&1 | FileCheck %s
+// CHECK: "-clear-ast-before-backend"
----------------
dblaikie wrote:
> This is a driver test, but not a very interesting one - it tests that -Xclang arguments are passed directyl to cc1, which is probably tested elsewhere already?
> 
> I'm not sure there's anything we could really test with the first RUN line - though since it's not a Driver test and doesn't need to be a Driver test - it should probably just test cc1 -clear-ast-before-backend directly rather than going through the driver+-Xclang
Might be worth fleshing this out somehow to observe some behavior? I'm not sure exactly how - not like we'd generally test other memory optimizations we might make without a flag to opt into them. But perhaps a simple Hello World, maybe with some optimizations applied (so making this one of those rare "actually check it going through some optimizations" - I guess ever -O0 with an always_inline function or the like to demonstrate that the optimizations were applied, etc)

Can't think of much else that wouldn't just be obnoxious in terms of memory usage - oh, unless there's some way to set an artificially low memory limit (some other tests might do this - clang/test/PCH/leakfiles.test puts a low ulimit for instance - some lldb and compiler-rt tests also set ulimits of various kinds to observe failures). An A/B test - showing some modest example hitting the memory limit without the flag, but passing with the flag, could be nice to have.


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https://reviews.llvm.org/D111105