| Message ID | 20240201103340.119081-3-ltaylorsimpson@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | Hexagon (target/hexagon) Enable more short-circuit packets | expand |
> -----Original Message----- > From: Taylor Simpson <ltaylorsimpson@gmail.com> > Sent: Thursday, February 1, 2024 4:34 AM > To: qemu-devel@nongnu.org > Cc: Brian Cain <bcain@quicinc.com>; Matheus Bernardino (QUIC) > <quic_mathbern@quicinc.com>; Sid Manning <sidneym@quicinc.com>; > Marco Liebel (QUIC) <quic_mliebel@quicinc.com>; > richard.henderson@linaro.org; philmd@linaro.org; ale@rev.ng; anjo@rev.ng; > ltaylorsimpson@gmail.com > Subject: [PATCH v2 2/3] Hexagon (target/hexagon) Enable more short-circuit > packets (scalar core) > > WARNING: This email originated from outside of Qualcomm. Please be wary > of any links or attachments, and do not enable macros. > > Look for read-after-write instead of overlap of reads and writes > > Here is an example with overalp but no read-after-write: > 0x000200fc: 0x38103876 { R0 = add(R0,R1); R6 = add(R6,R7) } > > BEFORE: > ---- 00000000000200fc > mov_i32 loc2,$0x0 > mov_i32 loc2,r0 > add_i32 loc3,loc2,r1 > mov_i32 loc2,loc3 > mov_i32 loc4,$0x0 > mov_i32 loc4,r6 > add_i32 loc5,loc4,r7 > mov_i32 loc4,loc5 > mov_i32 r0,loc2 > mov_i32 r6,loc4 > > AFTER: > ---- 00000000000200fc > add_i32 loc2,r0,r1 > mov_i32 r0,loc2 > add_i32 loc3,r6,r7 > mov_i32 r6,loc3 > > We can also short-circuit packets with .new values by reading from the > real destination instead of the temporary. > 0x00020100: 0x78005ff3 { R19 = #0xff > 0x00020104: 0x2002e204 if (cmp.eq(N19.new,R2)) jump:t PC+8 } > > BEFORE: > ---- 0000000000020100 > mov_i32 pc,$0x20108 > mov_i32 loc8,$0x0 > mov_i32 loc8,$0xff > setcond_i32 loc10,loc8,r2,eq > mov_i32 loc6,loc10 > mov_i32 r19,loc8 > add_i32 pkt_cnt,pkt_cnt,$0x2 > add_i32 insn_cnt,insn_cnt,$0x4 > brcond_i32 loc6,$0x0,eq,$L1 > goto_tb $0x0 > mov_i32 pc,$0x20108 > exit_tb $0x7fbb54000040 > set_label $L1 > goto_tb $0x1 > exit_tb $0x7fbb54000041 > set_label $L0 > exit_tb $0x7fbb54000043 > > AFTER: > ---- 0000000000020100 > mov_i32 pc,$0x20108 > mov_i32 r19,$0xff > setcond_i32 loc7,r19,r2,eq > mov_i32 loc4,loc7 > add_i32 pkt_cnt,pkt_cnt,$0x2 > add_i32 insn_cnt,insn_cnt,$0x4 > brcond_i32 loc4,$0x0,eq,$L1 > goto_tb $0x0 > mov_i32 pc,$0x20108 > exit_tb $0x7f9764000040 > set_label $L1 > goto_tb $0x1 > exit_tb $0x7f9764000041 > set_label $L0 > exit_tb $0x7f9764000043 > > Signed-off-by: Taylor Simpson <ltaylorsimpson@gmail.com> > --- > target/hexagon/translate.h | 13 +++++++------ > target/hexagon/translate.c | 21 ++++----------------- > 2 files changed, 11 insertions(+), 23 deletions(-) > > diff --git a/target/hexagon/translate.h b/target/hexagon/translate.h > index f06d71fc53..d5e7f49ad8 100644 > --- a/target/hexagon/translate.h > +++ b/target/hexagon/translate.h > @@ -38,12 +38,10 @@ typedef struct DisasContext { > int reg_log[REG_WRITES_MAX]; > int reg_log_idx; > DECLARE_BITMAP(regs_written, TOTAL_PER_THREAD_REGS); > - DECLARE_BITMAP(regs_read, TOTAL_PER_THREAD_REGS); > DECLARE_BITMAP(predicated_regs, TOTAL_PER_THREAD_REGS); > int preg_log[PRED_WRITES_MAX]; > int preg_log_idx; > DECLARE_BITMAP(pregs_written, NUM_PREGS); > - DECLARE_BITMAP(pregs_read, NUM_PREGS); > uint8_t store_width[STORES_MAX]; > bool s1_store_processed; > int future_vregs_idx; > @@ -68,6 +66,7 @@ typedef struct DisasContext { > bool is_tight_loop; > bool short_circuit; > bool has_hvx_helper; > + bool read_after_write; > TCGv new_value[TOTAL_PER_THREAD_REGS]; > TCGv new_pred_value[NUM_PREGS]; > TCGv pred_written; > @@ -88,13 +87,14 @@ static inline void ctx_log_pred_write(DisasContext > *ctx, int pnum) > > static inline void ctx_log_pred_read(DisasContext *ctx, int pnum) > { > - set_bit(pnum, ctx->pregs_read); > + if (test_bit(pnum, ctx->pregs_written)) { > + ctx->read_after_write = true; > + } > } > > static inline void ctx_log_pred_read_new(DisasContext *ctx, int pnum) > { > g_assert(test_bit(pnum, ctx->pregs_written)); > - set_bit(pnum, ctx->pregs_read); > } > > static inline void ctx_log_reg_write(DisasContext *ctx, int rnum, > @@ -125,13 +125,14 @@ static inline void > ctx_log_reg_write_pair(DisasContext *ctx, int rnum, > > static inline void ctx_log_reg_read(DisasContext *ctx, int rnum) > { > - set_bit(rnum, ctx->regs_read); > + if (test_bit(rnum, ctx->regs_written)) { > + ctx->read_after_write = true; > + } > } > > static inline void ctx_log_reg_read_new(DisasContext *ctx, int rnum) > { > g_assert(test_bit(rnum, ctx->regs_written)); > - set_bit(rnum, ctx->regs_read); > } > > static inline void ctx_log_reg_read_pair(DisasContext *ctx, int rnum) > diff --git a/target/hexagon/translate.c b/target/hexagon/translate.c > index 95579ae243..751ca71790 100644 > --- a/target/hexagon/translate.c > +++ b/target/hexagon/translate.c > @@ -1,5 +1,5 @@ > /* > - * Copyright(c) 2019-2023 Qualcomm Innovation Center, Inc. All Rights > Reserved. > + * Copyright(c) 2019-2024 Qualcomm Innovation Center, Inc. All Rights > Reserved. > * > * This program is free software; you can redistribute it and/or modify > * it under the terms of the GNU General Public License as published by > @@ -394,20 +394,8 @@ static bool need_commit(DisasContext *ctx) > } > } > > - /* Check for overlap between register reads and writes */ > - for (int i = 0; i < ctx->reg_log_idx; i++) { > - int rnum = ctx->reg_log[i]; > - if (test_bit(rnum, ctx->regs_read)) { > - return true; > - } > - } > - > - /* Check for overlap between predicate reads and writes */ > - for (int i = 0; i < ctx->preg_log_idx; i++) { > - int pnum = ctx->preg_log[i]; > - if (test_bit(pnum, ctx->pregs_read)) { > - return true; > - } > + if (ctx->read_after_write) { > + return true; > } > > /* Check for overlap between HVX reads and writes */ > @@ -466,6 +454,7 @@ static void analyze_packet(DisasContext *ctx) > { > Packet *pkt = ctx->pkt; > ctx->has_hvx_helper = false; > + ctx->read_after_write = false; > for (int i = 0; i < pkt->num_insns; i++) { > Insn *insn = &pkt->insn[i]; > ctx->insn = insn; > @@ -490,11 +479,9 @@ static void gen_start_packet(DisasContext *ctx) > ctx->next_PC = next_PC; > ctx->reg_log_idx = 0; > bitmap_zero(ctx->regs_written, TOTAL_PER_THREAD_REGS); > - bitmap_zero(ctx->regs_read, TOTAL_PER_THREAD_REGS); > bitmap_zero(ctx->predicated_regs, TOTAL_PER_THREAD_REGS); > ctx->preg_log_idx = 0; > bitmap_zero(ctx->pregs_written, NUM_PREGS); > - bitmap_zero(ctx->pregs_read, NUM_PREGS); > ctx->future_vregs_idx = 0; > ctx->tmp_vregs_idx = 0; > ctx->vreg_log_idx = 0; > -- > 2.34.1 Reviewed-by: Brian Cain <bcain@quicinc.com>
diff --git a/target/hexagon/translate.h b/target/hexagon/translate.h index f06d71fc53..d5e7f49ad8 100644 --- a/target/hexagon/translate.h +++ b/target/hexagon/translate.h @@ -38,12 +38,10 @@ typedef struct DisasContext { int reg_log[REG_WRITES_MAX]; int reg_log_idx; DECLARE_BITMAP(regs_written, TOTAL_PER_THREAD_REGS); - DECLARE_BITMAP(regs_read, TOTAL_PER_THREAD_REGS); DECLARE_BITMAP(predicated_regs, TOTAL_PER_THREAD_REGS); int preg_log[PRED_WRITES_MAX]; int preg_log_idx; DECLARE_BITMAP(pregs_written, NUM_PREGS); - DECLARE_BITMAP(pregs_read, NUM_PREGS); uint8_t store_width[STORES_MAX]; bool s1_store_processed; int future_vregs_idx; @@ -68,6 +66,7 @@ typedef struct DisasContext { bool is_tight_loop; bool short_circuit; bool has_hvx_helper; + bool read_after_write; TCGv new_value[TOTAL_PER_THREAD_REGS]; TCGv new_pred_value[NUM_PREGS]; TCGv pred_written; @@ -88,13 +87,14 @@ static inline void ctx_log_pred_write(DisasContext *ctx, int pnum) static inline void ctx_log_pred_read(DisasContext *ctx, int pnum) { - set_bit(pnum, ctx->pregs_read); + if (test_bit(pnum, ctx->pregs_written)) { + ctx->read_after_write = true; + } } static inline void ctx_log_pred_read_new(DisasContext *ctx, int pnum) { g_assert(test_bit(pnum, ctx->pregs_written)); - set_bit(pnum, ctx->pregs_read); } static inline void ctx_log_reg_write(DisasContext *ctx, int rnum, @@ -125,13 +125,14 @@ static inline void ctx_log_reg_write_pair(DisasContext *ctx, int rnum, static inline void ctx_log_reg_read(DisasContext *ctx, int rnum) { - set_bit(rnum, ctx->regs_read); + if (test_bit(rnum, ctx->regs_written)) { + ctx->read_after_write = true; + } } static inline void ctx_log_reg_read_new(DisasContext *ctx, int rnum) { g_assert(test_bit(rnum, ctx->regs_written)); - set_bit(rnum, ctx->regs_read); } static inline void ctx_log_reg_read_pair(DisasContext *ctx, int rnum) diff --git a/target/hexagon/translate.c b/target/hexagon/translate.c index 95579ae243..751ca71790 100644 --- a/target/hexagon/translate.c +++ b/target/hexagon/translate.c @@ -1,5 +1,5 @@ /* - * Copyright(c) 2019-2023 Qualcomm Innovation Center, Inc. All Rights Reserved. + * Copyright(c) 2019-2024 Qualcomm Innovation Center, Inc. All Rights Reserved. * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by @@ -394,20 +394,8 @@ static bool need_commit(DisasContext *ctx) } } - /* Check for overlap between register reads and writes */ - for (int i = 0; i < ctx->reg_log_idx; i++) { - int rnum = ctx->reg_log[i]; - if (test_bit(rnum, ctx->regs_read)) { - return true; - } - } - - /* Check for overlap between predicate reads and writes */ - for (int i = 0; i < ctx->preg_log_idx; i++) { - int pnum = ctx->preg_log[i]; - if (test_bit(pnum, ctx->pregs_read)) { - return true; - } + if (ctx->read_after_write) { + return true; } /* Check for overlap between HVX reads and writes */ @@ -466,6 +454,7 @@ static void analyze_packet(DisasContext *ctx) { Packet *pkt = ctx->pkt; ctx->has_hvx_helper = false; + ctx->read_after_write = false; for (int i = 0; i < pkt->num_insns; i++) { Insn *insn = &pkt->insn[i]; ctx->insn = insn; @@ -490,11 +479,9 @@ static void gen_start_packet(DisasContext *ctx) ctx->next_PC = next_PC; ctx->reg_log_idx = 0; bitmap_zero(ctx->regs_written, TOTAL_PER_THREAD_REGS); - bitmap_zero(ctx->regs_read, TOTAL_PER_THREAD_REGS); bitmap_zero(ctx->predicated_regs, TOTAL_PER_THREAD_REGS); ctx->preg_log_idx = 0; bitmap_zero(ctx->pregs_written, NUM_PREGS); - bitmap_zero(ctx->pregs_read, NUM_PREGS); ctx->future_vregs_idx = 0; ctx->tmp_vregs_idx = 0; ctx->vreg_log_idx = 0;
Look for read-after-write instead of overlap of reads and writes Here is an example with overalp but no read-after-write: 0x000200fc: 0x38103876 { R0 = add(R0,R1); R6 = add(R6,R7) } BEFORE: ---- 00000000000200fc mov_i32 loc2,$0x0 mov_i32 loc2,r0 add_i32 loc3,loc2,r1 mov_i32 loc2,loc3 mov_i32 loc4,$0x0 mov_i32 loc4,r6 add_i32 loc5,loc4,r7 mov_i32 loc4,loc5 mov_i32 r0,loc2 mov_i32 r6,loc4 AFTER: ---- 00000000000200fc add_i32 loc2,r0,r1 mov_i32 r0,loc2 add_i32 loc3,r6,r7 mov_i32 r6,loc3 We can also short-circuit packets with .new values by reading from the real destination instead of the temporary. 0x00020100: 0x78005ff3 { R19 = #0xff 0x00020104: 0x2002e204 if (cmp.eq(N19.new,R2)) jump:t PC+8 } BEFORE: ---- 0000000000020100 mov_i32 pc,$0x20108 mov_i32 loc8,$0x0 mov_i32 loc8,$0xff setcond_i32 loc10,loc8,r2,eq mov_i32 loc6,loc10 mov_i32 r19,loc8 add_i32 pkt_cnt,pkt_cnt,$0x2 add_i32 insn_cnt,insn_cnt,$0x4 brcond_i32 loc6,$0x0,eq,$L1 goto_tb $0x0 mov_i32 pc,$0x20108 exit_tb $0x7fbb54000040 set_label $L1 goto_tb $0x1 exit_tb $0x7fbb54000041 set_label $L0 exit_tb $0x7fbb54000043 AFTER: ---- 0000000000020100 mov_i32 pc,$0x20108 mov_i32 r19,$0xff setcond_i32 loc7,r19,r2,eq mov_i32 loc4,loc7 add_i32 pkt_cnt,pkt_cnt,$0x2 add_i32 insn_cnt,insn_cnt,$0x4 brcond_i32 loc4,$0x0,eq,$L1 goto_tb $0x0 mov_i32 pc,$0x20108 exit_tb $0x7f9764000040 set_label $L1 goto_tb $0x1 exit_tb $0x7f9764000041 set_label $L0 exit_tb $0x7f9764000043 Signed-off-by: Taylor Simpson <ltaylorsimpson@gmail.com> --- target/hexagon/translate.h | 13 +++++++------ target/hexagon/translate.c | 21 ++++----------------- 2 files changed, 11 insertions(+), 23 deletions(-)