From 34f760bac2c9a32afae150fbcc56ceba399d61de Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?V=C3=ADctor=20Colombo?= Date: Tue, 6 Sep 2022 09:55:18 -0300 Subject: target/ppc: Zero second doubleword in DFP instructions MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Starting at PowerISA v3.1, the second doubleword of the registers used to store results in DFP instructions are supposed to be zeroed. From the ISA, chapter 7.2.1.1 Floating-Point Registers: """ Chapter 4. Floating-Point Facility provides 32 64-bit FPRs. Chapter 5. Decimal Floating-Point also employs FPRs in decimal floating-point (DFP) operations. When VSX is implemented, the 32 FPRs are mapped to doubleword 0 of VSRs 0-31. (...) All instructions that operate on an FPR are redefined to operate on doubleword element 0 of the corresponding VSR. (...) and the contents of doubleword element 1 of the VSR corresponding to the target FPR or FPR pair for these instructions are set to 0. """ Before, the result stored at doubleword 1 was said to be undefined. With that, this patch changes the DFP facility to zero doubleword 1 when using set_dfp64 and set_dfp128. This fixes the behavior for ISA 3.1 while keeping the behavior correct for previous ones. Signed-off-by: Víctor Colombo Reviewed-by: Daniel Henrique Barboza Message-Id: <20220906125523.38765-4-victor.colombo@eldorado.org.br> Signed-off-by: Daniel Henrique Barboza --- target/ppc/dfp_helper.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/target/ppc/dfp_helper.c b/target/ppc/dfp_helper.c index 5ba74b2..be7aa53 100644 --- a/target/ppc/dfp_helper.c +++ b/target/ppc/dfp_helper.c @@ -42,13 +42,16 @@ static void get_dfp128(ppc_vsr_t *dst, ppc_fprp_t *dfp) static void set_dfp64(ppc_fprp_t *dfp, ppc_vsr_t *src) { - dfp->VsrD(0) = src->VsrD(1); + dfp[0].VsrD(0) = src->VsrD(1); + dfp[0].VsrD(1) = 0ULL; } static void set_dfp128(ppc_fprp_t *dfp, ppc_vsr_t *src) { dfp[0].VsrD(0) = src->VsrD(0); dfp[1].VsrD(0) = src->VsrD(1); + dfp[0].VsrD(1) = 0ULL; + dfp[1].VsrD(1) = 0ULL; } static void set_dfp128_to_avr(ppc_avr_t *dst, ppc_vsr_t *src) -- cgit v1.1