[PATCH] rs6000: Don't use TFmode for 128 bits fp constant in toc [PR110011]

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi,

As PR110011 shows, when encoding 128 bits fp constant into
toc, we adopts REAL_VALUE_TO_TARGET_LONG_DOUBLE which is
to find the first float mode with LONG_DOUBLE_TYPE_SIZE
bits of precision, it would be TFmode here.  But the 128
bits fp constant can be with mode IFmode or KFmode, which
doesn't necessarily have the same underlying float format
as the one of TFmode, like this PR exposes, with option
-mabi=ibmlongdouble TFmode has ibm_extended_format while
KFmode has ieee_quad_format, mixing up the formats (the
encoding/decoding ways) would cause unexpected results.

This patch is to make it use constant's own mode instead
of TFmode for real_to_target call.

Bootstrapped and regtested on powerpc64-linux-gnu P7/P8/P9 and
powerpc64le-linux-gnu P9 and P10.

I'll push this next week if no objections.

BR,
Kewen
-----
	PR target/110011

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (output_toc): Use its own mode of the
	128-bit float constant for real_to_target call.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr110011.c: New test.
---
 gcc/config/rs6000/rs6000.cc                 |  2 +-
 gcc/testsuite/gcc.target/powerpc/pr110011.c | 42 +++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr110011.c

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 3f129ea37d2..330c6a6fa5f 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -17314,7 +17314,7 @@ output_toc (FILE *file, rtx x, int labelno, machine_mode mode)
       if (DECIMAL_FLOAT_MODE_P (GET_MODE (x)))
 	REAL_VALUE_TO_TARGET_DECIMAL128 (*CONST_DOUBLE_REAL_VALUE (x), k);
       else
-	REAL_VALUE_TO_TARGET_LONG_DOUBLE (*CONST_DOUBLE_REAL_VALUE (x), k);
+	real_to_target (k, CONST_DOUBLE_REAL_VALUE (x), GET_MODE (x));

       if (TARGET_64BIT)
 	{
diff --git a/gcc/testsuite/gcc.target/powerpc/pr110011.c b/gcc/testsuite/gcc.target/powerpc/pr110011.c
new file mode 100644
index 00000000000..5b04d3e298a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr110011.c
@@ -0,0 +1,42 @@
+/* { dg-do run } */
+/* { dg-require-effective-target float128_runtime } */
+/* Force long double to be with IBM format here, to verify
+   _Float128 constant still uses its own format (IEEE) for
+   encoding rather than IBM format.  */
+/* { dg-options "-mfp-in-toc -mabi=ibmlongdouble" } */
+/* { dg-add-options float128 } */
+
+#define MPFR_FLOAT128_MAX 0x1.ffffffffffffffffffffffffffffp+16383f128
+
+__attribute__ ((noipa))
+_Float128 f128_max ()
+{
+  return MPFR_FLOAT128_MAX;
+}
+
+typedef union
+{
+  int w[4];
+  _Float128 f128;
+} U;
+
+int main ()
+{
+
+  U umax;
+  umax.f128 = f128_max ();
+  /* ieee float128 max:
+     7ffeffff ffffffff ffffffff ffffffff.  */
+  if (umax.w[1] != 0xffffffff || umax.w[2] != 0xffffffff)
+    __builtin_abort ();
+#ifdef __LITTLE_ENDIAN__
+  if (umax.w[0] != 0xffffffff || umax.w[3] != 0x7ffeffff)
+    __builtin_abort ();
+#else
+  if (umax.w[3] != 0xffffffff || umax.w[0] != 0x7ffeffff)
+    __builtin_abort ();
+#endif
+
+  return 0;
+}
+
--
2.31.1