Patchwork [07/10] ARM: Return correct result for single<->double conversion of NaN

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Submitter Peter Maydell
Date Dec. 6, 2010, 5 p.m.
Message ID <1291654811-29863-8-git-send-email-peter.maydell@linaro.org>
Download mbox | patch
Permalink /patch/74415/
State New
Headers show

Comments

Peter Maydell - Dec. 6, 2010, 5 p.m.
The ARM ARM defines that if the input to a single<->double conversion
is a NaN then the output is always forced to be a quiet NaN by setting
the most significant bit of the fraction part.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target-arm/helper.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)
Nathan Froyd - Dec. 6, 2010, 6:17 p.m.
On Mon, Dec 06, 2010 at 05:00:08PM +0000, Peter Maydell wrote:
> The ARM ARM defines that if the input to a single<->double conversion
> is a NaN then the output is always forced to be a quiet NaN by setting
> the most significant bit of the fraction part.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Nathan Froyd <froydnj@codesourcery.com>

-Nathan

Patch

diff --git a/target-arm/helper.c b/target-arm/helper.c
index 6d2a8f2..4bd1cd4 100644
--- a/target-arm/helper.c
+++ b/target-arm/helper.c
@@ -2528,12 +2528,20 @@  float32 VFP_HELPER(tosiz, d)(float64 x, CPUState *env)
 /* floating point conversion */
 float64 VFP_HELPER(fcvtd, s)(float32 x, CPUState *env)
 {
-    return float32_to_float64(x, &env->vfp.fp_status);
+    float64 r = float32_to_float64(x, &env->vfp.fp_status);
+    /* ARM requires that S<->D conversion of any kind of NaN generates
+     * a quiet NaN by forcing the most significant frac bit to 1.
+     */
+    return float64_maybe_silence_nan(r);
 }
 
 float32 VFP_HELPER(fcvts, d)(float64 x, CPUState *env)
 {
-    return float64_to_float32(x, &env->vfp.fp_status);
+    float32 r =  float64_to_float32(x, &env->vfp.fp_status);
+    /* ARM requires that S<->D conversion of any kind of NaN generates
+     * a quiet NaN by forcing the most significant frac bit to 1.
+     */
+    return float32_maybe_silence_nan(r);
 }
 
 /* VFP3 fixed point conversion.  */