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HowToSubmitABug.rst

Differential D56950

[docs] Prevent O0 optnone for opt input
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Authored by smeenai on Jan 18 2019, 5:09 PM.

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Reviewers

chandlerc
dblaikie
craig.topper

Commits

rGed2ebf82e70d: [docs] Prevent O0 optnone for opt input
rL352550: [docs] Prevent O0 optnone for opt input

Summary

If we just compile with -O0, clang will add optnone attributes
everywhere, so opt won't actually be able to perform any passes.
Instruct clang to not emit the optnone so opt can do its thing.

Diff Detail

Build Status

Buildable 27088
Build 27087: arc lint + arc unit

Event Timeline

smeenai created this revision.Jan 18 2019, 5:09 PM

Harbormaster completed remote builds in B27088: Diff 182646.Jan 18 2019, 5:09 PM

smeenai marked an inline comment as done.Jan 18 2019, 5:10 PM

smeenai added inline comments.

llvm/docs/HowToSubmitABug.rst
87	This is definitely over 80 columns, but I'm not sure if we're strict about that in the documentation, and what the best way to split it would be. Also, are there any preferences for `-O0 -Xclang -disable-O0-optnone` vs. `-O1 -Xclang -disable-llvm-passes` vs. `-O1 -Xclang -disable-llvm-optzns`?

craig.topper added a subscriber: craig.topper.Jan 18 2019, 5:25 PM

craig.topper added inline comments.

llvm/docs/HowToSubmitABug.rst
87	I think -disable-passes is preferred over -disable-llvm-optzns. That spelling is weird. Using -O1 -Xclang -disable-llvm-passes is going to more accurately give the IR. There are other differences that clang makes in -O0 other than the obvious optnone.

@ctopper comment

Harbormaster completed remote builds in B27090: Diff 182653.Jan 18 2019, 5:38 PM

smeenai marked an inline comment as done.Jan 18 2019, 5:38 PM

smeenai added inline comments.

llvm/docs/HowToSubmitABug.rst
87	Just for my knowledge, could you elaborate on some of the differences, if you happen to remember them off-hand?

craig.topper added inline comments.Jan 18 2019, 5:51 PM

llvm/docs/HowToSubmitABug.rst
87	I think TBAA metadata is skipped in -O0 as one example. You can grep for CodeGenOpts.OptimizationLevel in clang's lib/CodeGen/ directory for others.

Ping.

I might just commit for post-commit review, since @craig.topper weighed in on my main question above.

LGTM

This revision is now accepted and ready to land.Jan 29 2019, 2:16 PM

Closed by commit rL352550: [docs] Prevent O0 optnone for opt input (authored by smeenai). · Explain WhyJan 29 2019, 2:17 PM

This revision was automatically updated to reflect the committed changes.

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HowToSubmitABug.rst

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Diff 182646

llvm/docs/HowToSubmitABug.rst

	Show First 20 Lines • Show All 78 Lines • ▼ Show 20 Lines
	on the best way to use delta.			on the best way to use delta.

	.. _compile-time optimization bugs:			.. _compile-time optimization bugs:

	Compile-time optimization bugs			Compile-time optimization bugs
	------------------------------			------------------------------

	If you find that a bug crashes in the optimizer, compile your test-case to a			If you find that a bug crashes in the optimizer, compile your test-case to a
	``.bc`` file by passing "``-emit-llvm -O0 -c -o foo.bc``".			``.bc`` file by passing "``-emit-llvm -O0 -Xclang -disable-O0-optnone -c -o foo.bc``".
				smeenaiAuthorUnsubmitted Done Reply Inline Actions This is definitely over 80 columns, but I'm not sure if we're strict about that in the documentation, and what the best way to split it would be. Also, are there any preferences for `-O0 -Xclang -disable-O0-optnone` vs. `-O1 -Xclang -disable-llvm-passes` vs. `-O1 -Xclang -disable-llvm-optzns`? smeenai: This is definitely over 80 columns, but I'm not sure if we're strict about that in the…
				craig.topperUnsubmitted Not Done Reply Inline Actions I think -disable-passes is preferred over -disable-llvm-optzns. That spelling is weird. Using -O1 -Xclang -disable-llvm-passes is going to more accurately give the IR. There are other differences that clang makes in -O0 other than the obvious optnone. craig.topper: I think -disable-passes is preferred over -disable-llvm-optzns. That spelling is weird. Using…
				smeenaiAuthorUnsubmitted Done Reply Inline Actions Just for my knowledge, could you elaborate on some of the differences, if you happen to remember them off-hand? smeenai: Just for my knowledge, could you elaborate on some of the differences, if you happen to…
				craig.topperUnsubmitted Not Done Reply Inline Actions I think TBAA metadata is skipped in -O0 as one example. You can grep for CodeGenOpts.OptimizationLevel in clang's lib/CodeGen/ directory for others. craig.topper: I think TBAA metadata is skipped in -O0 as one example. You can grep for CodeGenOpts.
	Then run:			Then run:

	.. code-block:: bash			.. code-block:: bash

	opt -O3 -debug-pass=Arguments foo.bc -disable-output			opt -O3 -debug-pass=Arguments foo.bc -disable-output

	This command should do two things: it should print out a list of passes, and			This command should do two things: it should print out a list of passes, and
	then it should crash in the same way as clang. If it doesn't crash, please			then it should crash in the same way as clang. If it doesn't crash, please
	▲ Show 20 Lines • Show All 134 Lines • Show Last 20 Lines