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authorAndreas Sandberg <andreas@sandberg.pp.se>2013-06-18 16:30:06 +0200
committerAndreas Sandberg <andreas@sandberg.pp.se>2013-06-18 16:30:06 +0200
commita8e8c4f433fb3cce354950ba72136b84abb78015 (patch)
treec1b93c2399e0474da011b9aaaa324d4bd14b919e /src/arch/x86
parentc9c02efb99c0a982c116c7d1d8ed9a984c174198 (diff)
downloadgem5-a8e8c4f433fb3cce354950ba72136b84abb78015.tar.xz
x86: Fix loading of floating point constants
This changeset actually fixes two issues: * The lfpimm instruction didn't work correctly when applied to a floating point constant (it did work for integers containing the bit string representation of a constant) since it used reinterpret_cast to convert a double to a uint64_t. This caused a compilation error, at least, in gcc 4.6.3. * The instructions loading floating point constants in the x87 processor didn't work correctly since they just stored a truncated integer instead of a double in the floating point register. This changeset fixes the old microcode by using lfpimm instruction instead of the limm instructions.
Diffstat (limited to 'src/arch/x86')
-rw-r--r--src/arch/x86/isa/includes.isa1
-rw-r--r--src/arch/x86/isa/insts/x87/load_constants/load_0_1_or_pi.py6
-rw-r--r--src/arch/x86/isa/insts/x87/load_constants/load_logarithm.py8
-rw-r--r--src/arch/x86/isa/microops/limmop.isa4
-rw-r--r--src/arch/x86/utility.hh7
5 files changed, 17 insertions, 9 deletions
diff --git a/src/arch/x86/isa/includes.isa b/src/arch/x86/isa/includes.isa
index eda2ebceb..43565fda5 100644
--- a/src/arch/x86/isa/includes.isa
+++ b/src/arch/x86/isa/includes.isa
@@ -64,6 +64,7 @@ output header {{
#include "arch/x86/isa_traits.hh"
#include "arch/x86/registers.hh"
#include "arch/x86/types.hh"
+#include "arch/x86/utility.hh"
#include "base/misc.hh"
#include "cpu/static_inst.hh"
#include "mem/packet.hh"
diff --git a/src/arch/x86/isa/insts/x87/load_constants/load_0_1_or_pi.py b/src/arch/x86/isa/insts/x87/load_constants/load_0_1_or_pi.py
index cb8947312..9f22af89b 100644
--- a/src/arch/x86/isa/insts/x87/load_constants/load_0_1_or_pi.py
+++ b/src/arch/x86/isa/insts/x87/load_constants/load_0_1_or_pi.py
@@ -40,17 +40,17 @@
microcode = '''
def macroop FLDZ {
- limm ufp1, "double(0)"
+ lfpimm ufp1, 0.0
movfp st(-1), ufp1, spm=-1
};
def macroop FLD1 {
- limm ufp1, "double(1)"
+ lfpimm ufp1, 1.0
movfp st(-1), ufp1, spm=-1
};
def macroop FLDPI {
- limm ufp1, "double(3.14159265359)"
+ lfpimm ufp1, 3.14159265359
movfp st(-1), ufp1, spm=-1
};
diff --git a/src/arch/x86/isa/insts/x87/load_constants/load_logarithm.py b/src/arch/x86/isa/insts/x87/load_constants/load_logarithm.py
index 7e71c4006..88eb01086 100644
--- a/src/arch/x86/isa/insts/x87/load_constants/load_logarithm.py
+++ b/src/arch/x86/isa/insts/x87/load_constants/load_logarithm.py
@@ -40,22 +40,22 @@
microcode = '''
def macroop FLDL2E {
- limm ufp1, "double(1.44269504089)"
+ lfpimm ufp1, 1.44269504089
movfp st(-1), ufp1, spm=-1
};
def macroop FLDL2T {
- limm ufp1, "double(3.32192809489)"
+ lfpimm ufp1, 3.32192809489
movfp st(-1), ufp1, spm=-1
};
def macroop FLDLG2 {
- limm ufp1, "double(0.30102999566)"
+ lfpimm ufp1, 0.30102999566
movfp st(-1), ufp1, spm=-1
};
def macroop FLDLN2 {
- limm ufp1, "double(0.69314718056)"
+ lfpimm ufp1, 0.69314718056
movfp st(-1), ufp1, spm=-1
};
diff --git a/src/arch/x86/isa/microops/limmop.isa b/src/arch/x86/isa/microops/limmop.isa
index 9e88e4b94..2c61aaa45 100644
--- a/src/arch/x86/isa/microops/limmop.isa
+++ b/src/arch/x86/isa/microops/limmop.isa
@@ -140,8 +140,8 @@ let {{
self.dest = dest
if isinstance(imm, (int, long)):
imm = "ULL(%d)" % imm
- if isinstance(imm, float):
- imm = "reinterpret_cast<uint64_t>((double)(%d))"
+ elif isinstance(imm, float):
+ imm = "getDoubleBits(%.16f)" % imm
self.imm = imm
self.dataSize = dataSize
diff --git a/src/arch/x86/utility.hh b/src/arch/x86/utility.hh
index 6fc802f2f..48840ac77 100644
--- a/src/arch/x86/utility.hh
+++ b/src/arch/x86/utility.hh
@@ -134,6 +134,13 @@ namespace X86ISA
* @param val New rflags value to store in TC
*/
void setRFlags(ThreadContext *tc, uint64_t val);
+
+ /**
+ * Extract the bit string representing a double value.
+ */
+ inline uint64_t getDoubleBits(double val) {
+ return *(uint64_t *)(&val);
+ }
}
#endif // __ARCH_X86_UTILITY_HH__