* [PATCH 2/2] sim: riscv: Simplify the signed div by -1 code
@ 2024-04-15 14:46 Bernd Edlinger
0 siblings, 0 replies; only message in thread
From: Bernd Edlinger @ 2024-04-15 14:46 UTC (permalink / raw)
To: gdb-patches
This uses the idea from the previous patch to
simplify the code for non-overflowing signed
divisions by -1. This is no bug-fix but it
simplifies the code and avoids some unnecessary
branches.
---
sim/riscv/sim-main.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)
diff --git a/sim/riscv/sim-main.c b/sim/riscv/sim-main.c
index 515ff835223..e4b15b533ba 100644
--- a/sim/riscv/sim-main.c
+++ b/sim/riscv/sim-main.c
@@ -700,18 +700,16 @@ execute_m (SIM_CPU *cpu, unsigned_word iw, const struct riscv_opcode *op)
const char *rd_name = riscv_gpr_names_abi[rd];
const char *rs1_name = riscv_gpr_names_abi[rs1];
const char *rs2_name = riscv_gpr_names_abi[rs2];
- unsigned_word tmp, dividend_max;
+ unsigned_word tmp;
sim_cia pc = riscv_cpu->pc + 4;
- dividend_max = -((unsigned_word) 1 << (WITH_TARGET_WORD_BITSIZE - 1));
-
switch (op->match)
{
case MATCH_DIV:
TRACE_INSN (cpu, "div %s, %s, %s; // %s = %s / %s",
rd_name, rs1_name, rs2_name, rd_name, rs1_name, rs2_name);
- if (riscv_cpu->regs[rs1] == dividend_max && riscv_cpu->regs[rs2] == -1)
- tmp = dividend_max;
+ if (riscv_cpu->regs[rs2] == -1)
+ tmp = -riscv_cpu->regs[rs1];
else if (riscv_cpu->regs[rs2])
tmp = (signed_word) riscv_cpu->regs[rs1] /
(signed_word) riscv_cpu->regs[rs2];
@@ -793,7 +791,7 @@ execute_m (SIM_CPU *cpu, unsigned_word iw, const struct riscv_opcode *op)
case MATCH_REM:
TRACE_INSN (cpu, "rem %s, %s, %s; // %s = %s %% %s",
rd_name, rs1_name, rs2_name, rd_name, rs1_name, rs2_name);
- if (riscv_cpu->regs[rs1] == dividend_max && riscv_cpu->regs[rs2] == -1)
+ if (riscv_cpu->regs[rs2] == -1)
tmp = 0;
else if (riscv_cpu->regs[rs2])
tmp = (signed_word) riscv_cpu->regs[rs1]
--
2.39.2
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2024-04-15 14:46 [PATCH 2/2] sim: riscv: Simplify the signed div by -1 code Bernd Edlinger
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