nir/alu_to_scalar: Respect the exact ALU operation qualifier

Just setting builder->exact isn't sufficient because that only applies to
instructions that are built with the builder but instructions created
manually and only inserted using the builder are left alone.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Cc: "12.0" <mesa-stable@lists.freedesktop.org>

src/compiler/nir/nir_lower_alu_to_scalar.c

@@ -56,6 +56,7 @@ lower_reduction(nir_alu_instr *instr, nir_op chan_op, nir_op merge_op,
          nir_alu_src_copy(&chan->src[1], &instr->src[1], chan);
          chan->src[1].swizzle[0] = chan->src[1].swizzle[i];
       }
+      chan->exact = instr->exact;
 
       nir_builder_instr_insert(builder, &chan->instr);
 
@@ -229,6 +230,7 @@ lower_alu_instr_scalar(nir_alu_instr *instr, nir_builder *b)
       nir_alu_ssa_dest_init(lower, 1, instr->dest.dest.ssa.bit_size);
       lower->dest.saturate = instr->dest.saturate;
       comps[chan] = &lower->dest.dest.ssa;
+      lower->exact = instr->exact;
 
       nir_builder_instr_insert(b, &lower->instr);
    }