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Hexagon (target/hexagon) Short-circuit packet register writes
In certain cases, we can avoid the overhead of writing to hex_new_value and write directly to hex_gpr. We add need_commit field to DisasContext indicating if the end-of-packet commit is needed. If it is not needed, get_result_gpr() and get_result_gpr_pair() can return hex_gpr. We pass the ctx->need_commit to helpers when needed. Finally, we can early-exit from gen_reg_writes during packet commit. There are a few instructions whose semantics write to the result before reading all the inputs. Therefore, the idef-parser generated code is incompatible with short-circuit. We tell idef-parser to skip them. For debugging purposes, we add a cpu property to turn off short-circuit. When the short-circuit property is false, we skip the analysis and force the end-of-packet commit. Here's a simple example of the TCG generated for 0x004000b4: 0x7800c020 { R0 = #0x1 } BEFORE: ---- 004000b4 movi_i32 new_r0,$0x1 mov_i32 r0,new_r0 AFTER: ---- 004000b4 movi_i32 r0,$0x1 This patch reintroduces a use of check_for_attrib, so we remove the G_GNUC_UNUSED added earlier in this series. Signed-off-by: Taylor Simpson <tsimpson@quicinc.com> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Brian Cain <bcain@quicinc.com> Message-Id: <20230427230012.3800327-12-tsimpson@quicinc.com>
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16 changed files with 128 additions and 30 deletions
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@ -287,6 +287,8 @@ def gen_helper_function(f, tag, tagregs, tagimms):
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if hex_common.need_pkt_has_multi_cof(tag):
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f.write(", uint32_t pkt_has_multi_cof")
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if (hex_common.need_pkt_need_commit(tag)):
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f.write(", uint32_t pkt_need_commit")
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if hex_common.need_PC(tag):
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if i > 0:
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