[{"id":3684275,"web_url":"http://patchwork.ozlabs.org/comment/3684275/","msgid":"<97129d63-fe70-41f5-a103-61a7f6fd51d7@linaro.org>","list_archive_url":null,"date":"2026-04-29T21:18:49","subject":"Re: [PATCH 1/2] target/or1k: fix gen_mulu using signed multiply for\n unsigned operation","submitter":{"id":72104,"url":"http://patchwork.ozlabs.org/api/people/72104/","name":"Richard Henderson","email":"richard.henderson@linaro.org"},"content":"On 4/30/26 03:03, joel--- via qemu development wrote:\n> From: Joel Holdsworth \n> \n> gen_mulu() uses tcg_gen_muls2_i32 (signed widening multiply) but it\n> implements the l.mulu instruction which is an unsigned multiply. The\n> low 32-bit result is the same either way, but the high word written to\n> cpu_sr_cy (used for carry/overflow detection) will be incorrect when\n> the sign bits of the operands differ.\n> \n> Switch to tcg_gen_mulu2_i32 so the carry flag is computed correctly.\n> \n> Signed-off-by: Joel Holdsworth \n> ---\n> target/or1k/translate.c | 2 +-\n> 1 file changed, 1 insertion(+), 1 deletion(-)\n> \n> diff --git a/target/or1k/translate.c b/target/or1k/translate.c\n> index eb4485312f..1602e204fe 100644\n> --- a/target/or1k/translate.c\n> +++ b/target/or1k/translate.c\n> @@ -269,7 +269,7 @@ static void gen_mul(DisasContext *dc, TCGv_i32 dest,\n> static void gen_mulu(DisasContext *dc, TCGv_i32 dest,\n> TCGv_i32 srca, TCGv_i32 srcb)\n> {\n> - tcg_gen_muls2_i32(dest, cpu_sr_cy, srca, srcb);\n> + tcg_gen_mulu2_i32(dest, cpu_sr_cy, srca, srcb);\n> tcg_gen_setcondi_i32(TCG_COND_NE, cpu_sr_cy, cpu_sr_cy, 0);\n> \n> gen_ove_cy(dc);\n\nReviewed-by: Richard Henderson \n\nr~","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=QpnoXdb1;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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