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.

diff --git a/src/arch/x86/utility.cc b/src/arch/x86/utility.cc
index 41f5aee0b91bd54f921d3e29ae77cfe76e82c6ce..b50b99dfa1ee84854ed082c7f2ab66ea669a94bd 100644 (file)
--- a/src/arch/x86/utility.cc
+++ b/src/arch/x86/utility.cc
@@ -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 @@ genX87Tags(uint16_t ftw, uint8_t top, int8_t spm)
     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 --git a/src/arch/x86/utility.hh b/src/arch/x86/utility.hh
index dcf61bddbb83d2c5c190cc747742120ce13a544b..046b959db72e66d021401894f44f946e5e3f7d4e 100644 (file)
--- a/src/arch/x86/utility.hh
+++ b/src/arch/x86/utility.hh
@@ -187,6 +187,22 @@ namespace X86ISA
      * @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__