[Mesa-dev] [PATCH] radeonsi: disable sinking common instructions down to the end block

[Matt Arsenault]

> On Mar 14, 2017, at 17:21, Samuel Pitoiset <samuel.pitoiset at gmail.com> wrote:
> 
> Initially this was a workaround for a bug introduced in LLVM 4.0
> in the SimplifyCFG pass that caused image instrinsics to disappear
> (because they were badly sunk). Finally, this is a win because it
> decreases SGPR spilling and increases the number of waves a bit.
> 
> Although, shader-db results are good I think we might want to
> remove it in the future once the issue is fixed. For now, enable
> it for LLVM >= 4.0.
> 
> This also fixes a rendering issue with the speedometer in Dirt Rally.
> 
> More information can be found here https://reviews.llvm.org/D26348.
> 
> Thanks to Dave Airlie for the patch.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99484
> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
> ---
> 
> For those interested, here's the full shader-db report:
> 
> https://hastebin.com/osepehehat.pas
> 
> src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c | 6 ++++++
> 1 file changed, 6 insertions(+)
> 
> diff --git a/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c b/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
> index 5c63b732b3..4fb7a126e4 100644
> --- a/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
> +++ b/src/gallium/drivers/radeonsi/si_shader_tgsi_setup.c
> @@ -40,6 +40,7 @@
> #include <stdio.h>
> #include <llvm-c/Transforms/IPO.h>
> #include <llvm-c/Transforms/Scalar.h>
> +#include <llvm-c/Support.h>
> 
> /* Data for if/else/endif and bgnloop/endloop control flow structures.
>  */
> @@ -124,6 +125,11 @@ static void init_amdgpu_target()
> 	LLVMInitializeAMDGPUTarget();
> 	LLVMInitializeAMDGPUTargetMC();
> 	LLVMInitializeAMDGPUAsmPrinter();
> +
> +#if HAVE_LLVM >= 0x0400
> +	const char *argv[2] = {"mesa", "-simplifycfg-sink-common=false"};
> +	LLVMParseCommandLineOptions(2, argv, NULL);
> +#endif
> }

Probably should have a FIXME that this is a workaround and a link to an open bug to really fix these issues

-Matt