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[2001:1ae9:1c2:4c00:20f:c6b4:1e57:7965]) by smtp.gmail.com with ESMTPSA id qw25-20020a170906fcb900b009928b4e3b9fsm1073556ejb.114.2023.08.10.08.31.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Aug 2023 08:31:47 -0700 (PDT) Date: Thu, 10 Aug 2023 17:31:46 +0200 From: Andrew Jones To: Richard Bagley Cc: qemu-devel@nongnu.org, qemu-riscv@nongnu.org, alistair.francis@wdc.com, bmeng@tinylab.org, liweiwei@iscas.ac.cn, zhiwei_liu@linux.alibaba.com, palmer@rivosinc.com, dbarboza@ventanamicro.com Subject: Re: [PATCH] disas/riscv: Further correction to LUI disassembly Message-ID: <20230810-c9e1f2783168b48bc07a1aa2@orel> References: <20230731183320.410922-1-rbagley@ventanamicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230731183320.410922-1-rbagley@ventanamicro.com> Received-SPF: pass client-ip=2a00:1450:4864:20::52a; envelope-from=ajones@ventanamicro.com; helo=mail-ed1-x52a.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jul 31, 2023 at 11:33:20AM -0700, Richard Bagley wrote: > The recent commit 36df75a0a9 corrected one aspect of LUI disassembly > by recovering the immediate argument from the result of LUI with a > shift right by 12. However, the shift right will left-fill with the > sign. By applying a mask we recover an unsigned representation of the > 20-bit field (which includes a sign bit). > > Example: > 0xfffff000 >> 12 = 0xffffffff > 0xfffff000 >> 12 & 0xfffff = 0x000fffff > > Fixes: 36df75a0a9 ("riscv/disas: Fix disas output of upper immediates") > Signed-off-by: Richard Bagley > --- > disas/riscv.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/disas/riscv.c b/disas/riscv.c > index 4023e3fc65..690eb4a1ac 100644 > --- a/disas/riscv.c > +++ b/disas/riscv.c > @@ -4723,9 +4723,12 @@ static void format_inst(char *buf, size_t buflen, size_t tab, rv_decode *dec) > break; > case 'U': > fmt++; > - snprintf(tmp, sizeof(tmp), "%d", dec->imm >> 12); > - append(buf, tmp, buflen); > - if (*fmt == 'o') { > + if (*fmt == 'i') { > + snprintf(tmp, sizeof(tmp), "%d", dec->imm >> 12 & 0xfffff); Why are we correcting LUI's output, but still outputting sign-extended values for AUIPC? We can't assemble 'auipc a1, 0xffffffff' or 'auipc a1, -1' without getting Error: lui expression not in range 0..1048575 (and additionally for 0xffffffff) Error: value of 00000ffffffff000 too large for field of 4 bytes at 0000000000000000 either. (I see that the assembler's error messages state 'lui', but I was trying 'auipc'.) I'm using as from gnu binutils 2.40.0.20230214. (And, FWIW, I agree with Richard Henderson that these instructions should accept negative values.) Thanks, drew > + append(buf, tmp, buflen); > + } else if (*fmt == 'o') { > + snprintf(tmp, sizeof(tmp), "%d", dec->imm >> 12); > + append(buf, tmp, buflen); > while (strlen(buf) < tab * 2) { > append(buf, " ", buflen); > } > -- > 2.34.1 > >