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>,
qemu-devel@nongnu.org, groug@kaod.org, qemu-ppc@nongnu.org,
"Paul A. Clarke" <pc@us.ibm.com>,
David Gibson <david@gibson.dropbear.id.au>
Subject: [Qemu-devel] [PULL 42/42] ppc: Fix emulated single to double denormalized conversions
Date: Wed, 21 Aug 2019 17:25:42 +1000 [thread overview]
Message-ID: <20190821072542.23090-43-david@gibson.dropbear.id.au> (raw)
In-Reply-To: <20190821072542.23090-1-david@gibson.dropbear.id.au>
From: "Paul A. Clarke" <pc@us.ibm.com>
helper_todouble() was not properly converting any denormalized 32 bit
float to 64 bit double.
Fix-suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Paul A. Clarke <pc@us.ibm.com>
v2:
- Splitting patch "ppc: Three floating point fixes"; this is just one part.
- Original suggested "fix" was likely flawed. v2 is rewritten by
Richard Henderson (Thanks, Richard!); I reformatted the comments in a
couple of places, compiled, and tested.
Message-Id: <1566250936-14538-1-git-send-email-pc@us.ibm.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
target/ppc/fpu_helper.c | 17 +++++++++++++----
1 file changed, 13 insertions(+), 4 deletions(-)
diff --git a/target/ppc/fpu_helper.c b/target/ppc/fpu_helper.c
index 52bcda27a6..07bc9051b0 100644
--- a/target/ppc/fpu_helper.c
+++ b/target/ppc/fpu_helper.c
@@ -73,11 +73,20 @@ uint64_t helper_todouble(uint32_t arg)
/* Zero or Denormalized operand. */
ret = (uint64_t)extract32(arg, 31, 1) << 63;
if (unlikely(abs_arg != 0)) {
- /* Denormalized operand. */
- int shift = clz32(abs_arg) - 9;
- int exp = -126 - shift + 1023;
+ /*
+ * Denormalized operand.
+ * Shift fraction so that the msb is in the implicit bit position.
+ * Thus, shift is in the range [1:23].
+ */
+ int shift = clz32(abs_arg) - 8;
+ /*
+ * The first 3 terms compute the float64 exponent. We then bias
+ * this result by -1 so that we can swallow the implicit bit below.
+ */
+ int exp = -126 - shift + 1023 - 1;
+
ret |= (uint64_t)exp << 52;
- ret |= abs_arg << (shift + 29);
+ ret += (uint64_t)abs_arg << (52 - 23 + shift);
}
}
return ret;
--
2.21.0
next prev parent reply other threads:[~2019-08-21 7:58 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 7:25 [Qemu-devel] [PULL 00/42] ppc-for-4.2 queue 20190821 David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 01/42] spapr: quantify error messages regarding capability settings David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 02/42] spapr_iommu: Fix xlate trace to print translated address David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 03/42] hw: add compat machines for 4.2 David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 04/42] spapr_pci: Allow 2MiB and 16MiB IOMMU pagesizes by default David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 05/42] migration: Do not re-read the clock on pre_save in case of paused guest David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 06/42] target/ppc: Optimize emulation of lvsl and lvsr instructions David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 07/42] target/ppc: Optimize emulation of vsl and vsr instructions David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 08/42] target/ppc: move opcode decode tables to PowerPCCPU David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 09/42] target/ppc: Optimize emulation of vgbbd instruction David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 10/42] target/ppc: Optimize emulation of vclzd instruction David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 11/42] target/ppc: Optimize emulation of vclzw instruction David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 12/42] ppc: fix memory leak in spapr_caps_add_properties David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 13/42] ppc: fix memory leak in spapr_dt_drc() David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 14/42] ppc: fix leak in h_client_architecture_support David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 15/42] spapr: Implement dispatch tracking for tcg David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 16/42] spapr: Implement H_PROD David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 17/42] spapr: Implement H_CONFER David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 18/42] spapr: Implement H_JOIN David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 19/42] docs/specs: initial spec summary for Ultravisor-related hcalls David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 20/42] spapr: initial implementation for H_TPM_COMM/spapr-tpm-proxy David Gibson
2019-09-09 17:23 ` Peter Maydell
2019-09-09 17:51 ` Greg Kurz
2019-08-21 7:25 ` [Qemu-devel] [PULL 21/42] pseries: Update SLOF firmware image David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 22/42] ppc/xive: use an abstract type for XiveNotifier David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 23/42] ppc/xive: Implement TM_PULL_OS_CTX special command David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 24/42] ppc/xive: Provide backlog support David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 25/42] ppc/xive: Provide escalation support David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 26/42] ppc/xive: Provide unconditional " David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 27/42] ppc/xive: Provide silent " David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 28/42] ppc/xive: Improve 'info pic' support David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 29/42] machine: Add wakeup method to MachineClass David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 30/42] i386: use machine class ->wakeup method David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 31/42] spapr: Implement ibm,suspend-me David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 32/42] ppc: remove idle_timer logic David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 33/42] spapr/pci: Consolidate de-allocation of MSIs David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 34/42] spapr/pci: Free MSIs during reset David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 35/42] spapr/irq: Drop spapr_irq_msi_reset() David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 36/42] spapr: Implement better workaround in spapr-vty device David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 37/42] spapr/xive: Mask the EAS when allocating an IRQ David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 38/42] target/ppc: Add Directed Privileged Door-bell Exception State (DPDES) SPR David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 39/42] ppc: Add support for 'mffsl' instruction David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 40/42] ppc: conform to processor User's Manual for xscvdpspn David Gibson
2019-08-21 7:25 ` [Qemu-devel] [PULL 41/42] ppc: Fix emulated INFINITY and NAN conversions David Gibson
2019-08-21 7:25 ` David Gibson [this message]
2019-08-21 8:25 ` [Qemu-devel] [PULL 00/42] ppc-for-4.2 queue 20190821 no-reply
2019-08-21 14:18 ` Peter Maydell
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