radeonsi/gfx9: fix texture buffer objects and image buffers with IDXEN==0

Cc: 17.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

1 files changed, 34 insertions, 1 deletions

diff --git a/src/gallium/drivers/radeonsi/si_state.c b/src/gallium/drivers/radeonsi/si_state.c
index a55f024c843..8a8705f153d 100644
--- a/src/gallium/drivers/radeonsi/si_state.c
+++ b/src/gallium/drivers/radeonsi/si_state.c
@@ -2976,7 +2976,40 @@ si_make_buffer_descriptor(struct si_screen *screen, struct r600_resource *buf,
 	num_records = size / stride;
 	num_records = MIN2(num_records, (buf->b.b.width0 - offset) / stride);
 
-	if (screen->b.chip_class == VI)
+	/* The NUM_RECORDS field has a different meaning depending on the chip,
+	 * instruction type, STRIDE, and SWIZZLE_ENABLE.
+	 *
+	 * SI-CIK:
+	 * - If STRIDE == 0, it's in byte units.
+	 * - If STRIDE != 0, it's in units of STRIDE, used with inst.IDXEN.
+	 *
+	 * VI:
+	 * - For SMEM and STRIDE == 0, it's in byte units.
+	 * - For SMEM and STRIDE != 0, it's in units of STRIDE.
+	 * - For VMEM and STRIDE == 0 or SWIZZLE_ENABLE == 0, it's in byte units.
+	 * - For VMEM and STRIDE != 0 and SWIZZLE_ENABLE == 1, it's in units of STRIDE.
+	 * NOTE: There is incompatibility between VMEM and SMEM opcodes due to SWIZZLE_-
+	 *       ENABLE. The workaround is to set STRIDE = 0 if SWIZZLE_ENABLE == 0 when
+	 *       using SMEM. This can be done in the shader by clearing STRIDE with s_and.
+	 *       That way the same descriptor can be used by both SMEM and VMEM.
+	 *
+	 * GFX9:
+	 * - For SMEM and STRIDE == 0, it's in byte units.
+	 * - For SMEM and STRIDE != 0, it's in units of STRIDE.
+	 * - For VMEM and inst.IDXEN == 0 or STRIDE == 0, it's in byte units.
+	 * - For VMEM and inst.IDXEN == 1 and STRIDE != 0, it's in units of STRIDE.
+	 */
+	if (screen->b.chip_class >= GFX9)
+		/* When vindex == 0, LLVM sets IDXEN = 0, thus changing units
+		 * from STRIDE to bytes. This works around it by setting
+		 * NUM_RECORDS to at least the size of one element, so that
+		 * the first element is readable when IDXEN == 0.
+		 *
+		 * TODO: Fix this in LLVM, but do we need a new intrinsic where
+		 *       IDXEN is enforced?
+		 */
+		num_records = num_records ? MAX2(num_records, stride) : 0;
+	else if (screen->b.chip_class == VI)
 		num_records *= stride;
 
 	state[4] = 0;