This will be handy to avoid some ugly ternary operators in the next
patch, like:
fs_reg reg = (size == 0 ? null_reg_ud() : vgrf(..., size));
Because a zero-size register allocation is guaranteed not to ever be
read or written we can just return the null register. Another
possibility would be to actually allocate a zero-size VGRF what would
involve defining a zero-size register class in the register allocator
and a considerable amount of churn.
---
src/mesa/drivers/dri/i965/brw_fs_builder.h | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/src/mesa/drivers/dri/i965/brw_fs_builder.h
b/src/mesa/drivers/dri/i965/brw_fs_builder.h
index eea1eae..e7d5f8a 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_builder.h
+++ b/src/mesa/drivers/dri/i965/brw_fs_builder.h
@@ -160,10 +160,13 @@ namespace brw {
dst_reg
vgrf(enum brw_reg_type type, unsigned n = 1) const
{
- return dst_reg(GRF, shader->alloc.allocate(
- DIV_ROUND_UP(n * type_sz(type) * dispatch_width(),
- REG_SIZE)),
- type);
+ if (n > 0)
+ return dst_reg(GRF, shader->alloc.allocate(
+ DIV_ROUND_UP(n * type_sz(type) *
dispatch_width(),
+ REG_SIZE)),
+ type);
+ else
+ return retype(null_reg_ud(), type);
}
/**
--
2.4.3
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