From: David Gibson <david@gibson.dropbear.id.au>
To: peter.maydell@linaro.org
Cc: lvivier@redhat.com, aik@ozlabs.ru,
Richard Henderson <richard.henderson@linaro.org>,
groug@kaod.org, qemu-devel@nongnu.org, qemu-ppc@nongnu.org,
"Paul A. Clarke" <pc@us.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: [Qemu-devel] [PULL 08/19] ppc: Fix xscvdpspn for SNAN
Date: Thu, 29 Aug 2019 16:08:16 +1000 [thread overview]
Message-ID: <20190829060827.25731-9-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20190829060827.25731-1-david@gibson.dropbear.id.au>
From: "Paul A. Clarke" <pc@us.ibm.com>
The xscvdpspn instruction implements a non-arithmetic conversion.
In particular, NaNs are not silenced and rounding is not performed.
Rewrite to match the pseudocode for ConvertDPtoSP_NS() in the
Power 3.0B manual.
Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
Message-Id: <1566321964-1447-1-git-send-email-pc@us.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
[dwg: Replaced description with clearer version from rth]
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
target/ppc/fpu_helper.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index 07bc9051b0..c8e719272d 100644
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -2887,12 +2887,40 @@ void helper_xscvqpdp(CPUPPCState *env, uint32_t opcode,
uint64_t helper_xscvdpspn(CPUPPCState *env, uint64_t xb)
{
- uint64_t result;
+ uint64_t result, sign, exp, frac;
float_status tstat = env->fp_status;
set_float_exception_flags(0, &tstat);
- result = (uint64_t)float64_to_float32(xb, &tstat);
+ sign = extract64(xb, 63, 1);
+ exp = extract64(xb, 52, 11);
+ frac = extract64(xb, 0, 52) | 0x10000000000000ULL;
+
+ if (unlikely(exp == 0 && extract64(frac, 0, 52) != 0)) {
+ /* DP denormal operand. */
+ /* Exponent override to DP min exp. */
+ exp = 1;
+ /* Implicit bit override to 0. */
+ frac = deposit64(frac, 53, 1, 0);
+ }
+
+ if (unlikely(exp < 897 && frac != 0)) {
+ /* SP tiny operand. */
+ if (897 - exp > 63) {
+ frac = 0;
+ } else {
+ /* Denormalize until exp = SP min exp. */
+ frac >>= (897 - exp);
+ }
+ /* Exponent override to SP min exp - 1. */
+ exp = 896;
+ }
+
+ result = sign << 31;
+ result |= extract64(exp, 10, 1) << 30;
+ result |= extract64(exp, 0, 7) << 23;
+ result |= extract64(frac, 29, 23);
+
/* hardware replicates result to both words of the doubleword result. */
return (result << 32) | result;
}
--
2.21.0
next prev parent reply other threads:[~2019-08-29 6:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 6:08 [Qemu-devel] [PULL 00/19] ppc-for-4.2 queue 20190829 David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 01/19] ppc/pnv: Set default ram size to 1.75GB David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 03/19] ppc/pnv: add more dummy XSCOM addresses for the P9 CAPP David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 04/19] ppc/pnv: Generate phandle for the "interrupt-parent" property David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 05/19] ppc/pnv: Introduce PowerNV machines with fixed CPU models David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 06/19] tests/boot-serial-test: add support for all the PowerNV machines David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 07/19] ppc: Fix xsmaddmdp and friends David Gibson
2019-08-29 6:08 ` David Gibson [this message]
2019-08-29 6:08 ` [Qemu-devel] [PULL 09/19] spapr_pci: remove all child functions in function zero unplug David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 10/19] pseries: Fix compat_pvr on reset David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 11/19] target/ppc: Set float_tininess_before_rounding at cpu reset David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 12/19] target/ppc: Fix do_float_check_status vs inexact David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 13/19] target/ppc: Refactor emulation of vmrgew and vmrgow instructions David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 14/19] pseries: Update SLOF firmware image David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 15/19] powerpc/spapr: Add host threads parameter to ibm, get_system_parameter David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 16/19] spapr: Use SHUTDOWN_CAUSE_SUBSYSTEM_RESET for CAS reboots David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 17/19] spapr_pci: Advertise BAR reallocation capability David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 18/19] spapr/pci: Convert types to QEMU coding style David Gibson
2019-08-29 6:08 ` [Qemu-devel] [PULL 19/19] spapr: Set compat mode in spapr_core_plug() David Gibson
2019-09-04 8:17 ` [Qemu-devel] [PULL 00/19] ppc-for-4.2 queue 20190829 Peter Maydell
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