Set the default NaN pattern explicitly for the arm target.
This includes setting it for the old linux-user nwfpe emulation.
For nwfpe, our default doesn't match the real kernel, but we
avoid making a behaviour change in this commit.
Signed-off-by: Peter Maydell <peter.mayd...@linaro.org>
Reviewed-by: Richard Henderson <richard.hender...@linaro.org>
Message-id: 20241202131347.498124-41-peter.mayd...@linaro.org
---
linux-user/arm/nwfpe/fpa11.c | 5 +++++
target/arm/cpu.c | 2 ++
2 files changed, 7 insertions(+)
diff --git a/linux-user/arm/nwfpe/fpa11.c b/linux-user/arm/nwfpe/fpa11.c
index 8356beb52c6..0f1afbd91df 100644
--- a/linux-user/arm/nwfpe/fpa11.c
+++ b/linux-user/arm/nwfpe/fpa11.c
@@ -69,6 +69,11 @@ void resetFPA11(void)
* this late date.
*/
set_float_2nan_prop_rule(float_2nan_prop_s_ab, &fpa11->fp_status);
+ /*
+ * Use the same default NaN value as Arm VFP. This doesn't match
+ * the Linux kernel's nwfpe emulation, which uses an all-1s value.
+ */
+ set_float_default_nan_pattern(0b01000000, &fpa11->fp_status);
}
void SetRoundingMode(const unsigned int opcode)
diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index c81f6df3fca..4f7e18eb8e6 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -179,6 +179,7 @@ void arm_register_el_change_hook(ARMCPU *cpu,
ARMELChangeHookFn *hook,
* the pseudocode function the arguments are in the order c, a, b.
* * 0 * Inf + NaN returns the default NaN if the input NaN is quiet,
* and the input NaN if it is signalling
+ * * Default NaN has sign bit clear, msb frac bit set
*/
static void arm_set_default_fp_behaviours(float_status *s)
{
@@ -186,6 +187,7 @@ static void arm_set_default_fp_behaviours(float_status *s)
set_float_2nan_prop_rule(float_2nan_prop_s_ab, s);
set_float_3nan_prop_rule(float_3nan_prop_s_cab, s);
set_float_infzeronan_rule(float_infzeronan_dnan_if_qnan, s);
+ set_float_default_nan_pattern(0b01000000, s);
}
static void cp_reg_reset(gpointer key, gpointer value, gpointer opaque)
--
2.34.1
