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[PATCH, PR59833]: Fix sNaN handling in ARM float to double conversion


On ARM soft-float, the float to double conversion doesn't convert a sNaN
to qNaN as the IEEE Std 754 standard mandates:

"Under default exception handling, any operation signaling an invalid
operation exception and for which a floating-point result is to be
delivered shall deliver a quiet NaN."

Given the soft float ARM code ignores exceptions and always provides a
result, a float to double conversion of a signaling NaN should return a
quiet NaN. Fix this in extendsfdf2.

gcc/ChangeLog:

	PR target/59833
	* config/arm/ieee754-df.S (extendsfdf2): Convert sNaN to qNaN.

gcc/testsuite/ChangeLog:

	* gcc.dg/pr59833.c: New testcase.
---
 gcc/testsuite/gcc.dg/pr59833.c | 18 ++++++++++++++++++
 libgcc/config/arm/ieee754-df.S | 10 +++++++---
 2 files changed, 25 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr59833.c

diff --git a/gcc/testsuite/gcc.dg/pr59833.c b/gcc/testsuite/gcc.dg/pr59833.c
new file mode 100644
index 0000000..e0e4ed5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr59833.c
@@ -0,0 +1,18 @@
+/* { dg-do run { target { *-*-linux* *-*-gnu* } } } */
+/* { dg-options "-O0 -lm" } */
+/* { dg-require-effective-target issignaling } */
+
+#define _GNU_SOURCE
+#include <math.h>
+
+int main (void)
+{
+  float sNaN = __builtin_nansf ("");
+  double x = (double) sNaN;
+  if (issignaling(x))
+  {
+    __builtin_abort();
+  }
+
+  return 0;
+}
diff --git a/libgcc/config/arm/ieee754-df.S b/libgcc/config/arm/ieee754-df.S
index a2aac70..1ecaa9d 100644
--- a/libgcc/config/arm/ieee754-df.S
+++ b/libgcc/config/arm/ieee754-df.S
@@ -507,11 +507,15 @@ ARM_FUNC_ALIAS aeabi_f2d extendsfdf2
 	eorne	xh, xh, #0x38000000	@ fixup exponent otherwise.
 	RETc(ne)			@ and return it.
 
-	teq	r2, #0			@ if actually 0
-	do_it	ne, e
-	teqne	r3, #0xff000000		@ or INF or NAN
+	bics	r2, r2, #0xff000000	@ isolate mantissa
+	do_it	eq			@ if 0, that is ZERO or INF,
 	RETc(eq)			@ we are done already.
 
+	teq	r3, #0xff000000		@ check for NAN
+	do_it	eq, t
+	orreq	xh, xh, #0x00080000	@ change to quiet NAN
+	RETc(eq)			@ and return it.
+
 	@ value was denormalized.  We can normalize it now.
 	do_push	{r4, r5, lr}
 	.cfi_adjust_cfa_offset 12   @ CFA is now sp + previousOffset + 12

-- 
Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net


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