linux-kernel - Re: [PATCH 3/7] drm/vc4: Add a bitmap of branch targets during shader validation.

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Message-ID: <87fura1qsh.fsf@eliezer.anholt.net>
Date:	Fri, 15 Jul 2016 15:26:38 -0700
From:	Eric Anholt <eric@...olt.net>
To:	dri-devel@...ts.freedesktop.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] drm/vc4: Add a bitmap of branch targets during shader validation.

Eric Anholt <eric@...olt.net> writes:

> This isn't used yet, it's just a first step toward loop validation.
> During the main parsing of instructions, we need to know when we hit a
> new basic block so that we can reset validated state.
>
> Signed-off-by: Eric Anholt <eric@...olt.net>
> ---
>  drivers/gpu/drm/vc4/vc4_qpu_defines.h      |  12 +++
>  drivers/gpu/drm/vc4/vc4_validate_shaders.c | 114 ++++++++++++++++++++++++++++-
>  2 files changed, 124 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_qpu_defines.h b/drivers/gpu/drm/vc4/vc4_qpu_defines.h
> index d5c2f3c85ebb..82ef0e525d55 100644
> --- a/drivers/gpu/drm/vc4/vc4_qpu_defines.h
> +++ b/drivers/gpu/drm/vc4/vc4_qpu_defines.h

> +		/* The actual branch target is the instruction after the delay
> +		 * slots, plus whatever byte offset is in the low 32 bits of
> +		 * the instruction.  Make sure we're not branching beyond the
> +		 * end of the shader object.
> +		 */
> +		if (branch_imm % sizeof(inst) != 0) {
> +			DRM_ERROR("branch target not aligned\n");
> +			return false;
> +		};

Last change before pull request: I dropped the stray ';' that kbuild
test robot caught.

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