From mint-bounce@lists.fishpool.fi Wed Jun 9 13:52:33 2010 X-ME-UUID: 20100609174828271.421F38002460@mwinf2816.orange.fr Date: Wed, 9 Jun 2010 19:48:27 +0200 From: Patrice Mandin To: Mint list Subject: [MiNT] Optimisation bug in gcc 4 ? Message-Id: <20100609194827.0a54c39a.mandin.patrice@orange.fr> Organization: Chez moi X-Mailer: Sylpheed 2.5.0 (GTK+ 2.12.12; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="Multipart=_Wed__9_Jun_2010_19_48_27_+0200_3YKPt5bfZiQ1BDzD" X-ecartis-version: Ecartis v1.0.0 Sender: mint-bounce@lists.fishpool.fi Errors-to: mint-bounce@lists.fishpool.fi X-original-sender: mandin.patrice@orange.fr Precedence: bulk List-help: List-unsubscribe: List-Id: X-List-ID: List-subscribe: List-owner: List-post: This is a multi-part message in MIME format. --Multipart=_Wed__9_Jun_2010_19_48_27_+0200_3YKPt5bfZiQ1BDzD Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Hello, I just encountered a strange optimisation bug with gcc 4 (4.4.2 more precisely), I hope it's fixed with 4.5. Source is attached, this is a small test case. I have a variable 'vidix_capability_t vidx_cap'. The purpose of the function vdxGetCapability() (which is xbios #404) is to fill this structure. Then I test the field vidx_cap.flags for a given combination of bits in this field. Depending on this test, I either exit the program, or call myvidix_func(). The bug: with gcc 4.4.2 (starting at -O1 level), it assumes the field has a constant value, optimizes the test by removing it, and the code that follows, thus also wiping out entirely the function myvidix_func from the generated assembly code (use -save-temps to prevent deletion of it). It does not happen with -O0, or with gcc 3. I don't know if it's a problem in gcc, or in the definition of the function (that uses mintlib defined trap_14_wl macro). Note: both 4.4.2 and 3.x are cross-compilers. --=20 Patrice Mandin WWW: http://pmandin.atari.org/ Programmeur Linux, Atari Sp=E9cialit=E9: D=E9veloppement, jeux "who writes the code, decides" --Multipart=_Wed__9_Jun_2010_19_48_27_+0200_3YKPt5bfZiQ1BDzD Content-Type: text/x-csrc; name="yuvtest.c" Content-Disposition: attachment; filename="yuvtest.c" Content-Transfer-Encoding: 7bit #include typedef struct vidix_capability_s { char name[64]; /* Driver name */ char author[64]; /* Author name */ #define TYPE_OUTPUT 0x00000000 /* Is a video playback device */ #define TYPE_CAPTURE 0x00000001 /* Is a capture device */ #define TYPE_CODEC 0x00000002 /* Device supports hw (de)coding */ #define TYPE_FX 0x00000004 /* Is a video effects device */ int type; /* Device type, see below */ unsigned reserved0[4]; int maxwidth; int maxheight; int minwidth; int minheight; int maxframerate; /* -1 if unlimited */ #define FLAG_NONE 0x00000000 /* No flags defined */ #define FLAG_DMA 0x00000001 /* Card can use DMA */ #define FLAG_EQ_DMA 0x00000002 /* Card can use DMA only if src pitch == dest pitch */ #define FLAG_UPSCALER 0x00000010 /* Card supports hw upscaling */ #define FLAG_DOWNSCALER 0x00000020 /* Card supports hw downscaling */ #define FLAG_SUBPIC 0x00001000 /* Card supports DVD subpictures */ #define FLAG_EQUALIZER 0x00002000 /* Card supports equalizer */ unsigned flags; /* Feature flags, see above */ unsigned short vendor_id; unsigned short device_id; unsigned reserved1[4]; }vidix_capability_t; #define vdxGetCapability(to) (long)trap_14_wl((short)(404),(long)(to)) static void myvidix_func(void); void main(void) { vidix_capability_t vidx_cap; if (vdxGetCapability(&vidx_cap) != 0) { Cconws("vidix: Get capability failed\r\n"); return; } if ((vidx_cap.flags & (FLAG_UPSCALER|FLAG_DOWNSCALER)) != FLAG_UPSCALER|FLAG_DOWNSCALER) { Cconws("vidix: Need upscaler and downscaler\n"); return; } myvidix_func(); } static void myvidix_func(void) { Cconws("Hello vidix\r\n"); } --Multipart=_Wed__9_Jun_2010_19_48_27_+0200_3YKPt5bfZiQ1BDzD--