From f6898f2b554e88255909bdd6bd0f7a91d99c446b Mon Sep 17 00:00:00 2001 From: Kenneth Graunke Date: Fri, 8 Jun 2018 14:24:16 -0700 Subject: [PATCH] intel/compiler: Properly consider UBO loads that cross 32B boundaries. The UBO push analysis pass incorrectly assumed that all values would fit within a 32B chunk, and only recorded a bit for the 32B chunk containing the starting offset. For example, if a UBO contained the following, tightly packed: vec4 a; // [0, 16) float b; // [16, 20) vec4 c; // [20, 36) then, c would start at offset 20 / 32 = 0 and end at 36 / 32 = 1, which means that we ought to record two 32B chunks in the bitfield. Similarly, dvec4s would suffer from the same problem. v2: Rewrite the accounting, my calculations were wrong. v3: Write a comment about partial values (requested by Jason). Reviewed-by: Rafael Antognolli [v1] Reviewed-by: Jason Ekstrand [v3] --- src/intel/compiler/brw_nir_analyze_ubo_ranges.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/src/intel/compiler/brw_nir_analyze_ubo_ranges.c b/src/intel/compiler/brw_nir_analyze_ubo_ranges.c index d58fe3dd2e3..cd5137da06e 100644 --- a/src/intel/compiler/brw_nir_analyze_ubo_ranges.c +++ b/src/intel/compiler/brw_nir_analyze_ubo_ranges.c @@ -137,14 +137,26 @@ analyze_ubos_block(struct ubo_analysis_state *state, nir_block *block) const int block = block_const->u32[0]; const int offset = offset_const->u32[0] / 32; - /* Won't fit in our bitfield */ + /* Avoid shifting by larger than the width of our bitfield, as this + * is undefined in C. Even if we require multiple bits to represent + * the entire value, it's OK to record a partial value - the backend + * is capable of falling back to pull loads for later components of + * vectors, as it has to shrink ranges for other reasons anyway. + */ if (offset >= 64) continue; + /* The value might span multiple 32-byte chunks. */ + const int bytes = nir_intrinsic_dest_components(intrin) * + (nir_dest_bit_size(intrin->dest) / 8); + const int start = ROUND_DOWN_TO(offset_const->u32[0], 32); + const int end = ALIGN(offset_const->u32[0] + bytes, 32); + const int chunks = (end - start) / 32; + /* TODO: should we count uses in loops as higher benefit? */ struct ubo_block_info *info = get_block_info(state, block); - info->offsets |= 1ull << offset; + info->offsets |= ((1ull << chunks) - 1) << offset; info->uses[offset]++; } } -- 2.11.0