[PATCH AUTOSEL 4.9 18/30] x86: math-emu: Hide clang warnings for 16-bit overflow

Sasha Levin
2019-07-26T13:45:03Z

From: Arnd Bergmann <arnd@arndb.de>

[ Upstream commit 29e7e9664aec17b94a9c8c5a75f8d216a206aa3a ]

clang warns about a few parts of the math-emu implementation
where a 16-bit integer becomes negative during assignment:

arch/x86/math-emu/poly_tan.c:88:35: error: implicit conversion from 'int' to 'short' changes value from 49216 to -16320 [-Werror,-Wconstant-conversion]
(0x41 + EXTENDED_Ebias) | SIGN_Negative);
~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~
arch/x86/math-emu/fpu_emu.h:180:58: note: expanded from macro 'setexponent16'
#define setexponent16(x,y) { (*(short *)&((x)->exp)) = (y); }
~ ^
arch/x86/math-emu/reg_constant.c:37:32: error: implicit conversion from 'int' to 'short' changes value from 49085 to -16451 [-Werror,-Wconstant-conversion]
FPU_REG const CONST_PI2extra = MAKE_REG(NEG, -66,
^~~~~~~~~~~~~~~~~~
arch/x86/math-emu/reg_constant.c:21:25: note: expanded from macro 'MAKE_REG'
((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/math-emu/reg_constant.c:48:28: error: implicit conversion from 'int' to 'short' changes value from 65535 to -1 [-Werror,-Wconstant-conversion]
FPU_REG const CONST_QNaN = MAKE_REG(NEG, EXP_OVER, 0x00000000, 0xC0000000);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/math-emu/reg_constant.c:21:25: note: expanded from macro 'MAKE_REG'
((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

The code is correct as is, so add a typecast to shut up the warnings.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190712090816.350668-1-arnd@arndb.de
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/x86/math-emu/fpu_emu.h | 2 +-
arch/x86/math-emu/reg_constant.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/math-emu/fpu_emu.h b/arch/x86/math-emu/fpu_emu.h
index afbc4d805d66..df5aee5402c4 100644
--- a/arch/x86/math-emu/fpu_emu.h
+++ b/arch/x86/math-emu/fpu_emu.h
@@ -176,7 +176,7 @@ static inline void reg_copy(FPU_REG const *x, FPU_REG *y)
#define setexponentpos(x,y) { (*(short *)&((x)->exp)) = \
((y) + EXTENDED_Ebias) & 0x7fff; }
#define exponent16(x) (*(short *)&((x)->exp))
-#define setexponent16(x,y) { (*(short *)&((x)->exp)) = (y); }
+#define setexponent16(x,y) { (*(short *)&((x)->exp)) = (u16)(y); }
#define addexponent(x,y) { (*(short *)&((x)->exp)) += (y); }
#define stdexp(x) { (*(short *)&((x)->exp)) += EXTENDED_Ebias; }

diff --git a/arch/x86/math-emu/reg_constant.c b/arch/x86/math-emu/reg_constant.c
index 00548354912f..382093c5072b 100644
--- a/arch/x86/math-emu/reg_constant.c
+++ b/arch/x86/math-emu/reg_constant.c
@@ -17,7 +17,7 @@
#include "control_w.h"

#define MAKE_REG(s, e, l, h) { l, h, \
- ((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
+ (u16)((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }

FPU_REG const CONST_1 = MAKE_REG(POS, 0, 0x00000000, 0x80000000);
#if 0
--
2.20.1