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

[Samuel Pitoiset]

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
 }
 
 static once_flag init_amdgpu_target_once_flag = ONCE_FLAG_INIT;
-- 
2.12.0