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From: "j-etienne at users dot sourceforge.net" <gcc-bugzilla@gcc.gnu.org> To: gcc-bugs@gcc.gnu.org Subject: [Bug ada/59772] New: Floating point constants are not correctly encoded on AVR target Date: Sat, 11 Jan 2014 22:47:00 -0000 [thread overview] Message-ID: <bug-59772-4@http.gcc.gnu.org/bugzilla/> (raw) http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59772 Bug ID: 59772 Summary: Floating point constants are not correctly encoded on AVR target Product: gcc Version: unknown Status: UNCONFIRMED Severity: critical Priority: P3 Component: ada Assignee: unassigned at gcc dot gnu.org Reporter: j-etienne at users dot sourceforge.net In code compiled for AVR target, the floating point constants are not correct in the generated code. Sample code (specification first, then body) : ------------- package Float_Test is function Div_Test (Value : Float) return Float; function Perimeter_Test (Value : Float) return Float; end Float_Test; package body Float_Test is K_Denominator : constant Float := Float (4096); K_Pi : constant Float := 3.1415927; function Div_Test (Value : Float) return Float is begin return (Value / K_Denominator); end Div_Test; function Perimeter_Test (Value : Float) return Float is begin return (Value * K_Pi); end Perimeter_Test; end Float_Test; ------------- When I commpile this sample code, with the following command : avr-gcc -Wall -Wextra -fno-strict-aliasing -fwrapv -fno-aggressive-loop-optimizations -mmcu=at90usb1287 -Os -S -gnatp -I ~/Programmation/Unix/gcc-4.8.2/gcc/ada float_test.adb -fdump-tree-original -gnatD It generates wrong values for both floating point constants : ------------- .file "float_test.adb" __SP_H__ = 0x3e __SP_L__ = 0x3d __SREG__ = 0x3f __RAMPZ__ = 0x3b __tmp_reg__ = 0 __zero_reg__ = 1 .global __divsf3 .text .global float_test__div_test .type float_test__div_test, @function float_test__div_test: /* prologue: function */ /* frame size = 0 */ /* stack size = 0 */ .L__stack_usage = 0 ldi r18,0 ldi r19,0 movw r20,r18 call __divsf3 ret .size float_test__div_test, .-float_test__div_test .global __mulsf3 .global float_test__perimeter_test .type float_test__perimeter_test, @function float_test__perimeter_test: /* prologue: function */ /* frame size = 0 */ /* stack size = 0 */ .L__stack_usage = 0 ldi r18,0 ldi r19,lo8(-80) ldi r20,lo8(125) ldi r21,lo8(58) call __mulsf3 ret .size float_test__perimeter_test, .-float_test__perimeter_test .global float_test_E .data .type float_test_E, @object .size float_test_E, 2 float_test_E: .zero 2 .ident "GCC: (GNU) 4.8.2" .global __do_copy_data ------------- The denominator provided as argument to divsf3 is 0.0 instead of 4096, and the constant term provided as argument to mulsf3 is 0.000967741 instead of 3.12415927 I'm using a cross GCC for AVR target hosted on MacOSX 10.9. avr-gcc -v gives : Using built-in specs. COLLECT_GCC=avr-gcc COLLECT_LTO_WRAPPER=/opt/avr-ada-test/libexec/gcc/avr/4.8.2/lto-wrapper Target: avr Configured with: ../gcc-4.8.2/configure --prefix=/opt/avr-ada-test --target=avr --program-prefix=avr- --disable-shared --disable-nls --disable-libssp --with-system-zlib --disable-libada --enable-languages=ada,c --enable-cpp --with-dwarf2 --enable-version-specific-runtime-libs --with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local Thread model: single gcc version 4.8.2 (GCC) Please note that I reproduced the same behaviour on a x86-linux host. I first stumbled upon this bug when migrating my application to AVR GCC 4.7.2 using the RTS from AVR-Ada. With GCC 4.8.2, I tried several "system.ads" locations : the one from the AVR Ada RTS, from the native compiler, from the GCC source tree, and always got the same result. I noticed that in the GNAT debug file "float_test.adb.dg" , the constants are correct : ------------- float_test__k_denominator : constant float := [8388608.0*2**(-11)]; float_test__k_pi : constant float := [13176795.0*2**(-22)]; function float_test__div_test (value : float) return float is begin return (value / float_test__k_denominator); end float_test__div_test; function float_test__perimeter_test (value : float) return float is begin return (value * float_test__k_pi); end float_test__perimeter_test; ------------- While in the "original" tree dump "float_test.adb.003t.original", they are not (and have the values that are eventually found in the machine code) : ------------- Float_Test.Div_Test (const float value) { return (float) value / 0.0; Float_Test.Perimeter_Test (const float value) { return (float) value * 9.677410125732421875e-4; ------------- The encoding was correct with GCC 4.5
next reply other threads:[~2014-01-11 22:47 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2014-01-11 22:47 j-etienne at users dot sourceforge.net [this message] 2014-01-12 11:21 ` [Bug ada/59772] [4.7/4.8/4.9 regression ] floating-point constants are not correctly encoded ebotcazou at gcc dot gnu.org 2014-01-12 11:23 ` [Bug ada/59772] [4.7/4.8/4.9 regression] " ebotcazou at gcc dot gnu.org 2014-01-12 14:29 ` ebotcazou at gcc dot gnu.org 2014-01-12 14:30 ` ebotcazou at gcc dot gnu.org 2014-01-12 14:30 ` ebotcazou at gcc dot gnu.org 2014-01-12 14:32 ` ebotcazou at gcc dot gnu.org
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