i965/fs: Fix nir_op_fsign of absolute value.
This does point at the front-end emitting silly code that could have been optimized out, but the current fsign implementation would emit bogus IR if abs was set for the argument (because it would apply the abs modifier on an unsigned integer type), and we shouldn't rely on the upper layer's optimization passes for correctness. Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
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@ -701,7 +701,14 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
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break;
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case nir_op_fsign: {
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if (type_sz(op[0].type) < 8) {
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if (op[0].abs) {
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/* Straightforward since the source can be assumed to be
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* non-negative.
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*/
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set_condmod(BRW_CONDITIONAL_NZ, bld.MOV(result, op[0]));
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set_predicate(BRW_PREDICATE_NORMAL, bld.MOV(result, brw_imm_f(1.0f)));
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} else if (type_sz(op[0].type) < 8) {
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/* AND(val, 0x80000000) gives the sign bit.
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*
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* Predicated OR ORs 1.0 (0x3f800000) with the sign bit if val is not
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