On Mon, 12 Aug 2019, Segher Boessenkool wrote: > (define_insn "add_truncdfsf3" > [(set (match_operand:SF 0 "gpc_reg_operand" "=f,wa") > (float_truncate:SF > (plus:DF (match_operand:DF 1 "gpc_reg_operand" "%d,wa") > (match_operand:DF 2 "gpc_reg_operand" "d,wa"))))]
That sort of pattern is incorrect for a fused operation such as fadd, because combine could match it for code that is supposed to do separate addition and narrowing conversion. The RTL needs to be something that does *not* match the combination of separate operations (just as fma has its own RTL, and a separate pass is responsible for converting separate operations to fused ones in the -ffp-contract=fast case where it's permitted). -- Joseph S. Myers jos...@codesourcery.com
