On Thu, 19 Jul 2012 13:54:57 +0100
Paul Brook <p...@codesourcery.com> wrote:
> > But, that means EABI-conformant callers are also perfectly entitled
> > to sign-extend half-float values before calling our helper functions
> > (although GCC itself won't do that). Using "unsigned int" and taking
> > care to only examine the low-order bits of the value in the helper
> > function itself serves to fix the latent bug, is compatible with
> > existing code, allows us to be conformant with the eabi, and allows
> > use of aliases to make the __gnu and __aeabi functions the same.
>
> As long as LTO never sees this mismatch we should be fine :-) AFAIK
> we don't curently have any way of expressing the actual ABI.
Let's not worry about that for now :-).
> > The patch no longer applied as-is, so I've updated it (attached,
> > re-tested). Note that there are no longer any target-independent
> > changes (though I'm not certain that the symbol versions are still
> > correct).
> >
> > OK to apply?
>
> I think this deserves a comment in the source. Otherwise it's liable
> to get "fixed" in the future :-) Something allong the lines of
> "While the EABI describes the arguments to the half-float helper
> routines as 'short', it does not require that they be extended to
> full register width. The normal ABI requres that the caller sign/zero
> extend short values to 32 bit. We use unsigned int arguments to
> prevent the gcc making assumptions about the high half of the
> register."
Here's a version with an explanatory comment. I also fixed a couple of
minor formatting nits I noticed (they don't upset the diff too much, I
don't think).
OK?
Julian
commit f858cdd91188784794418b3456d06172df654dc3
Author: Julian Brown <jbr...@mentor.com>
Date: Wed Jul 18 08:43:12 2012 -0700
EABI half-precision helper function names.
diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index ff46dd9..c22c2b7 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -1238,12 +1238,12 @@ arm_init_libfuncs (void)
/* Conversions. */
set_conv_libfunc (trunc_optab, HFmode, SFmode,
(arm_fp16_format == ARM_FP16_FORMAT_IEEE
- ? "__gnu_f2h_ieee"
- : "__gnu_f2h_alternative"));
+ ? "__aeabi_f2h"
+ : "__aeabi_f2h_alt"));
set_conv_libfunc (sext_optab, SFmode, HFmode,
(arm_fp16_format == ARM_FP16_FORMAT_IEEE
- ? "__gnu_h2f_ieee"
- : "__gnu_h2f_alternative"));
+ ? "__aeabi_h2f"
+ : "__aeabi_h2f_alt"));
/* Arithmetic. */
set_optab_libfunc (add_optab, HFmode, NULL);
diff --git a/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-5.C b/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-5.C
index 92bc8a9..738d26d 100644
--- a/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-5.C
+++ b/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-5.C
@@ -13,3 +13,5 @@
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h\[a-z\]*_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h2f_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_f2h_ieee" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_h2f" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_f2h" } } */
diff --git a/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-6.C b/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-6.C
index ae40b1e..a0e09c8 100644
--- a/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-6.C
+++ b/gcc/testsuite/g++.dg/ext/arm-fp16/arm-fp16-ops-6.C
@@ -13,3 +13,5 @@
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h\[a-z\]*_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h2f_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_f2h_ieee" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_h2f" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_f2h" } } */
diff --git a/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-5.c b/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-5.c
index 92bc8a9..738d26d 100644
--- a/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-5.c
+++ b/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-5.c
@@ -13,3 +13,5 @@
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h\[a-z\]*_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h2f_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_f2h_ieee" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_h2f" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_f2h" } } */
diff --git a/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-6.c b/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-6.c
index ae40b1e..a0e09c8 100644
--- a/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-6.c
+++ b/gcc/testsuite/gcc.dg/torture/arm-fp16-ops-6.c
@@ -13,3 +13,5 @@
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h\[a-z\]*_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_h2f_ieee" } } */
/* { dg-final { scan-assembler-not "\tbl\t__gnu_f2h_ieee" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_h2f" } } */
+/* { dg-final { scan-assembler-not "\tbl\t__aeabi_f2h" } } */
diff --git a/libgcc/config/arm/fp16.c b/libgcc/config/arm/fp16.c
index 936caeb..0fb2fe4 100644
--- a/libgcc/config/arm/fp16.c
+++ b/libgcc/config/arm/fp16.c
@@ -22,10 +22,19 @@
see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
<http://www.gnu.org/licenses/>. */
-static inline unsigned short
-__gnu_f2h_internal(unsigned int a, int ieee)
+/* Note: While the EABI (Run-time ABI for the ARM (R) Architecture, IHI 0043C)
+ describes the helper routine arguments and return types representing
+ half-float values using the type 'short', it does not require that they be
+ extended to full register width.
+ The ABI normally requires that the caller sign or zero extends short (or
+ unsigned short) values to 32 bits. We use unsigned int arguments and return
+ types to prevent GCC making assumptions about the high halves of the
+ registers in question. */
+
+static inline unsigned int
+__gnu_f2h_internal (unsigned int a, int ieee)
{
- unsigned short sign = (a >> 16) & 0x8000;
+ unsigned int sign = (a >> 16) & 0x8000;
int aexp = (a >> 23) & 0xff;
unsigned int mantissa = a & 0x007fffff;
unsigned int mask;
@@ -95,10 +104,10 @@ __gnu_f2h_internal(unsigned int a, int ieee)
return sign | (((aexp + 14) << 10) + (mantissa >> 13));
}
-unsigned int
-__gnu_h2f_internal(unsigned short a, int ieee)
+static inline unsigned int
+__gnu_h2f_internal (unsigned int a, int ieee)
{
- unsigned int sign = (unsigned int)(a & 0x8000) << 16;
+ unsigned int sign = (a & 0x00008000) << 16;
int aexp = (a >> 10) & 0x1f;
unsigned int mantissa = a & 0x3ff;
@@ -120,26 +129,33 @@ __gnu_h2f_internal(unsigned short a, int ieee)
return sign | (((aexp + 0x70) << 23) + (mantissa << 13));
}
-unsigned short
-__gnu_f2h_ieee(unsigned int a)
+#define ALIAS(src, dst) \
+ typeof (src) dst __attribute__ ((alias (#src)));
+
+unsigned int
+__gnu_f2h_ieee (unsigned int a)
{
- return __gnu_f2h_internal(a, 1);
+ return __gnu_f2h_internal (a, 1);
}
+ALIAS (__gnu_f2h_ieee, __aeabi_f2h)
unsigned int
-__gnu_h2f_ieee(unsigned short a)
+__gnu_h2f_ieee (unsigned int a)
{
- return __gnu_h2f_internal(a, 1);
+ return __gnu_h2f_internal (a, 1);
}
+ALIAS (__gnu_h2f_ieee, __aeabi_h2f)
-unsigned short
-__gnu_f2h_alternative(unsigned int x)
+unsigned int
+__gnu_f2h_alternative (unsigned int x)
{
- return __gnu_f2h_internal(x, 0);
+ return __gnu_f2h_internal (x, 0);
}
+ALIAS (__gnu_f2h_alternative, __aeabi_f2h_alt)
unsigned int
-__gnu_h2f_alternative(unsigned short a)
+__gnu_h2f_alternative (unsigned int a)
{
- return __gnu_h2f_internal(a, 0);
+ return __gnu_h2f_internal (a, 0);
}
+ALIAS (__gnu_h2f_alternative, __aeabi_h2f_alt)
diff --git a/libgcc/config/arm/libgcc-bpabi.ver b/libgcc/config/arm/libgcc-bpabi.ver
index 3ba8364..5bb5f04 100644
--- a/libgcc/config/arm/libgcc-bpabi.ver
+++ b/libgcc/config/arm/libgcc-bpabi.ver
@@ -106,3 +106,10 @@ GCC_3.5 {
GCC_4.3.0 {
_Unwind_Backtrace
}
+
+GCC_4.7.0 {
+ __aeabi_f2h
+ __aeabi_f2h_alt
+ __aeabi_h2f
+ __aeabi_h2f_alt
+}
diff --git a/libgcc/config/arm/sfp-machine.h b/libgcc/config/arm/sfp-machine.h
index a89d05a..f2d7a37 100644
--- a/libgcc/config/arm/sfp-machine.h
+++ b/libgcc/config/arm/sfp-machine.h
@@ -99,7 +99,7 @@ typedef int __gcc_CMPtype __attribute__ ((mode (__libgcc_cmp_return__)));
#define __fixdfdi __aeabi_d2lz
#define __fixunsdfdi __aeabi_d2ulz
#define __floatdidf __aeabi_l2d
-#define __extendhfsf2 __gnu_h2f_ieee
-#define __truncsfhf2 __gnu_f2h_ieee
+#define __extendhfsf2 __aeabi_h2f
+#define __truncsfhf2 __aeabi_f2h
#endif /* __ARM_EABI__ */
diff --git a/libgcc/config/arm/t-bpabi b/libgcc/config/arm/t-bpabi
index e79cbd7..adf977a 100644
--- a/libgcc/config/arm/t-bpabi
+++ b/libgcc/config/arm/t-bpabi
@@ -3,9 +3,8 @@ LIB1ASMFUNCS += _aeabi_lcmp _aeabi_ulcmp _aeabi_ldivmod _aeabi_uldivmod
# Add the BPABI C functions.
LIB2ADD += $(srcdir)/config/arm/bpabi.c \
- $(srcdir)/config/arm/unaligned-funcs.c
-
-LIB2ADD_ST += $(srcdir)/config/arm/fp16.c
+ $(srcdir)/config/arm/unaligned-funcs.c \
+ $(srcdir)/config/arm/fp16.c
LIB2ADDEH = $(srcdir)/config/arm/unwind-arm.c \
$(srcdir)/config/arm/libunwind.S \
diff --git a/libgcc/config/arm/t-symbian b/libgcc/config/arm/t-symbian
index d573157..248bf78 100644
--- a/libgcc/config/arm/t-symbian
+++ b/libgcc/config/arm/t-symbian
@@ -13,7 +13,7 @@ LIB1ASMFUNCS += \
_fixsfsi _fixunssfsi
# Include half-float helpers.
-LIB2ADD_ST += $(srcdir)/config/arm/fp16.c
+LIB2ADD += $(srcdir)/config/arm/fp16.c
# Include the gcc personality routine
LIB2ADDEH = $(srcdir)/unwind-c.c $(srcdir)/config/arm/pr-support.c
