Mesa (master): radeonsi: add a workaround for weird s_buffer_load_dword behavior on SI
Marek Olšák
mareko at kemper.freedesktop.org
Thu Oct 26 14:44:43 UTC 2017
Module: Mesa
Branch: master
Commit: 3f8e3c2bd8f54ae6817f7496be47f4e1a8860d9c
URL: http://cgit.freedesktop.org/mesa/mesa/commit/?id=3f8e3c2bd8f54ae6817f7496be47f4e1a8860d9c
Author: Marek Olšák <marek.olsak at amd.com>
Date: Sun Oct 22 15:54:23 2017 +0200
radeonsi: add a workaround for weird s_buffer_load_dword behavior on SI
See my LLVM patch which fixes the root cause.
Users have to apply this patch and then they have 2 choices:
- Downgrade to LLVM 5.0
- Update to LLVM git after my LLVM patch is pushed.
It won't be possible to use current and earlier development version
of LLVM 6.0.
Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>
Cc: 17.3 <mesa-stable at lists.freedesktop.org>
---
src/gallium/drivers/radeonsi/si_shader.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index 4bf2a45eeb..4456026ac8 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -2013,14 +2013,21 @@ static LLVMValueRef fetch_constant(
* code reducing SIMD wave occupancy from 8 to 2 in many cases.
*
* Using s_buffer_load_dword (x1) seems to be the best option right now.
+ *
+ * LLVM 5.0 on SI doesn't insert a required s_nop between SALU setting
+ * a descriptor and s_buffer_load_dword using it, so we can't expand
+ * the pointer into a full descriptor like below. We have to use
+ * s_load_dword instead. The only case when LLVM 5.0 would select
+ * s_buffer_load_dword (that we have to prevent) is when we use use
+ * a literal offset where we don't need bounds checking.
*/
-#if 0 /* keep this codepath disabled */
- if (!reg->Register.Indirect) {
+ if (ctx->screen->b.chip_class == SI &&
+ HAVE_LLVM < 0x0600 &&
+ !reg->Register.Indirect) {
addr = LLVMBuildLShr(ctx->ac.builder, addr, LLVMConstInt(ctx->i32, 2, 0), "");
LLVMValueRef result = ac_build_load_invariant(&ctx->ac, ptr, addr);
return bitcast(bld_base, type, result);
}
-#endif
/* Do the bounds checking with a descriptor, because
* doing computation and manual bounds checking of 64-bit
More information about the mesa-commit
mailing list