changeset 2dbc34e3b922 in /z/repo/gem5
details: http://repo.gem5.org/gem5?cmd=changeset;node=2dbc34e3b922
description:
x86: Add support routines to load and store 80-bit floats
The x87 FPU on x86 supports extended floating point. We currently
handle all floating point on x86 as double and don't support 80-bit
loads/stores. This changeset add a utility function to load and
convert 80-bit floats to doubles (loadFloat80) and another function to
store doubles as 80-bit floats (storeFloat80). Both functions use
libfputils to do the conversion in software. The functions are
currently not used, but are required to handle floating point in KVM
and to properly support all x87 loads/stores.
diffstat:
src/arch/x86/utility.cc | 17 +++++++++++++++++
src/arch/x86/utility.hh | 16 ++++++++++++++++
2 files changed, 33 insertions(+), 0 deletions(-)
diffs (58 lines):
diff -r 68d6b600d51f -r 2dbc34e3b922 src/arch/x86/utility.cc
--- a/src/arch/x86/utility.cc Mon Sep 30 09:40:26 2013 +0200
+++ b/src/arch/x86/utility.cc Mon Sep 30 09:42:30 2013 +0200
@@ -44,6 +44,7 @@
#include "arch/x86/utility.hh"
#include "arch/x86/x86_traits.hh"
#include "cpu/base.hh"
+#include "fputils/fp80.h"
#include "sim/system.hh"
namespace X86ISA {
@@ -351,4 +352,20 @@
return ftw;
}
+double
+loadFloat80(const void *_mem)
+{
+ const fp80_t *fp80((const fp80_t *)_mem);
+
+ return fp80_cvtd(*fp80);
+}
+
+void
+storeFloat80(void *_mem, double value)
+{
+ fp80_t *fp80((fp80_t *)_mem);
+
+ *fp80 = fp80_cvfd(value);
+}
+
} // namespace X86_ISA
diff -r 68d6b600d51f -r 2dbc34e3b922 src/arch/x86/utility.hh
--- a/src/arch/x86/utility.hh Mon Sep 30 09:40:26 2013 +0200
+++ b/src/arch/x86/utility.hh Mon Sep 30 09:42:30 2013 +0200
@@ -187,6 +187,22 @@
* @return New value of the FTW register.
*/
uint16_t genX87Tags(uint16_t ftw, uint8_t top, int8_t spm);
+
+ /**
+ * Load an 80-bit float from memory and convert it to double.
+ *
+ * @param mem Pointer to an 80-bit float.
+ * @return double representation of the 80-bit float.
+ */
+ double loadFloat80(const void *mem);
+
+ /**
+ * Convert and store a double as an 80-bit float.
+ *
+ * @param mem Pointer to destination for the 80-bit float.
+ * @param value Double precision float to store.
+ */
+ void storeFloat80(void *mem, double value);
}
#endif // __ARCH_X86_UTILITY_HH__
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