According to IEEE 754 2008 4.3 'Rounding-direction attributes' the
rounding mode of the target format needs to be used. By not setting
the value so far we have always used the DFP rounding mode.
gcc/ChangeLog:
2018-09-06 Andreas Krebbel <kreb...@linux.ibm.com>
* config/s390/s390.md (PFPO_RND_MODE_DFP, PFPO_RND_MODE_BFP): New
constants.
("trunc<BFP:mode><DFP_ALL:mode>2")
("trunc<DFP_ALL:mode><BFP:mode>2")
("extend<BFP:mode><DFP_ALL:mode>2")
("extend<DFP_ALL:mode><BFP:mode>2"): Set proper rounding mode
according to the target operand type.
gcc/testsuite/ChangeLog:
2018-09-06 Andreas Krebbel <kreb...@linux.ibm.com>
* gcc.target/s390/dfp_to_bfp_rounding.c: New test.
---
gcc/config/s390/s390.md | 28 ++++++++++++++++++---
.../gcc.target/s390/dfp_to_bfp_rounding.c | 29 ++++++++++++++++++++++
2 files changed, 53 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/s390/dfp_to_bfp_rounding.c
diff --git a/gcc/config/s390/s390.md b/gcc/config/s390/s390.md
index ddf8608..537ed35 100644
--- a/gcc/config/s390/s390.md
+++ b/gcc/config/s390/s390.md
@@ -404,6 +404,10 @@
; Bitposition of operand types
(PFPO_OP0_TYPE_SHIFT 16)
(PFPO_OP1_TYPE_SHIFT 8)
+ ; Decide whether current DFP or BFD rounding mode should be used
+ ; for the conversion.
+ (PFPO_RND_MODE_DFP 0)
+ (PFPO_RND_MODE_BFP 1)
])
; Immediate operands for tbegin and tbeginc
@@ -5377,9 +5381,13 @@
{
HOST_WIDE_INT flags;
+ /* According to IEEE 754 2008 4.3 'Rounding-direction attributes' the
+ rounding mode of the target format needs to be used. */
+
flags = (PFPO_CONVERT |
PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP0_TYPE_SHIFT |
- PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP1_TYPE_SHIFT);
+ PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP1_TYPE_SHIFT |
+ PFPO_RND_MODE_DFP);
operands[2] = GEN_INT (flags);
})
@@ -5399,9 +5407,13 @@
{
HOST_WIDE_INT flags;
+ /* According to IEEE 754 2008 4.3 'Rounding-direction attributes' the
+ rounding mode of the target format needs to be used. */
+
flags = (PFPO_CONVERT |
PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP0_TYPE_SHIFT |
- PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP1_TYPE_SHIFT);
+ PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP1_TYPE_SHIFT |
+ PFPO_RND_MODE_BFP);
operands[2] = GEN_INT (flags);
})
@@ -5442,9 +5454,13 @@
{
HOST_WIDE_INT flags;
+ /* According to IEEE 754 2008 4.3 'Rounding-direction attributes' the
+ rounding mode of the target format needs to be used. */
+
flags = (PFPO_CONVERT |
PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP0_TYPE_SHIFT |
- PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP1_TYPE_SHIFT);
+ PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP1_TYPE_SHIFT |
+ PFPO_RND_MODE_DFP);
operands[2] = GEN_INT (flags);
})
@@ -5464,9 +5480,13 @@
{
HOST_WIDE_INT flags;
+ /* According to IEEE 754 2008 4.3 'Rounding-direction attributes' the
+ rounding mode of the target format needs to be used. */
+
flags = (PFPO_CONVERT |
PFPO_OP_TYPE_<BFP:MODE> << PFPO_OP0_TYPE_SHIFT |
- PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP1_TYPE_SHIFT);
+ PFPO_OP_TYPE_<DFP_ALL:MODE> << PFPO_OP1_TYPE_SHIFT |
+ PFPO_RND_MODE_BFP);
operands[2] = GEN_INT (flags);
})
diff --git a/gcc/testsuite/gcc.target/s390/dfp_to_bfp_rounding.c
b/gcc/testsuite/gcc.target/s390/dfp_to_bfp_rounding.c
new file mode 100644
index 0000000..9a32abf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/dfp_to_bfp_rounding.c
@@ -0,0 +1,29 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -mzarch -march=z10" } */
+
+/* According to IEEE 754 2008 4.3 Conversion operations between
+ different radixes must use the rounding mode of the target radix.
+ On S/390 this means passing the right value in GPR0 to PFPO
+ instruction. */
+
+#include <fenv.h>
+
+double __attribute__((noclone,noinline))
+convert (_Decimal64 in)
+{
+ return (double)in;
+}
+
+int
+main ()
+{
+ fesetround (FE_UPWARD);
+
+ if (convert (1e-325DD) != __DBL_DENORM_MIN__)
+ __builtin_abort ();
+
+ fesetround (FE_DOWNWARD);
+
+ if (convert (-1e-325DD) != -__DBL_DENORM_MIN__)
+ __builtin_abort ();
+}
--
2.7.4
