1 files changed, 28 insertions, 0 deletions
diff --git a/gdb/i387-tdep.c b/gdb/i387-tdep.c
index ff369f9..1552565 100644
--- a/gdb/i387-tdep.c
+++ b/gdb/i387-tdep.c
@@ -734,3 +734,31 @@ i387_tag (const unsigned char *raw)
 	}
     }
 }
+
+/* Prepare the FPU stack in REGCACHE for a function return.  */
+
+void
+i387_return_value (struct gdbarch *gdbarch, struct regcache *regcache)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+  ULONGEST fstat;
+
+  /* Define I387_ST0_REGNUM such that we use the proper
+     definitions for the architecture.  */
+#define I387_ST0_REGNUM tdep->st0_regnum
+
+  /* Set the top of the floating-point register stack to 7.  The
+     actual value doesn't really matter, but 7 is what a normal
+     function return would end up with if the program started out with
+     a freshly initialized FPU.  */
+  regcache_raw_read_unsigned (regcache, I387_FSTAT_REGNUM, &fstat);
+  fstat |= (7 << 11);
+  regcache_raw_write_unsigned (regcache, I387_FSTAT_REGNUM, fstat);
+
+  /* Mark %st(1) through %st(7) as empty.  Since we set the top of the
+     floating-point register stack to 7, the appropriate value for the
+     tag word is 0x3fff.  */
+  regcache_raw_write_unsigned (regcache, I387_FTAG_REGNUM, 0x3fff);
+
+#undef I387_ST0_REGNUM
+}