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Old 11-08-2010, 02:22 AM
"brian m. carlson"
Default Bug#602785: gcc-4.5: should optimize bitwise operations

Package: gcc-4.5
Version: 4.5.1-9
Severity: wishlist

The attached file (not preprocessed because of the macros) uses two
macros F and G. F and G are completely equivalent[0]. As a result, r1
and r2 are guaranteed to be exactly equal always. I would like gcc, at
level -O3, to basically optimize the code to "return 0;". At the very
least, I would like G to be optimized to use one fewer instruction, like

I realize that this may be difficult, and that's why I filed it as

[0] MD5 specifies G as a component function, but most implementers use F
instead because it uses one fewer instruction.

-- System Information:
Debian Release: squeeze/sid
APT prefers unstable
APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.36-rc6-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages gcc-4.5 depends on:
ii binutils The GNU assembler, linker and bina
ii cpp-4.5 4.5.1-9 The GNU C preprocessor
ii gcc-4.5-base 4.5.1-9 The GNU Compiler Collection (base
ii libc6 2.11.2-7 Embedded GNU C Library: Shared lib
ii libcloog-ppl0 0.15.9-2 the Chunky Loop Generator (runtime
ii libelfg0 0.8.13-1 an ELF object file access library
ii libgcc1 1:4.5.1-9 GCC support library
ii libgmp3c2 2:4.3.2+dfsg-1 Multiprecision arithmetic library
ii libgmpxx4ldbl 2:4.3.2+dfsg-1 Multiprecision arithmetic library
ii libgomp1 4.5.1-9 GCC OpenMP (GOMP) support library
ii libmpc2 0.8.2-1+b1 multiple precision complex floatin
ii libmpfr4 3.0.0-2 multiple precision floating-point
ii libppl-c2 0.10.2-9 Parma Polyhedra Library (C interfa
ii libppl7 0.10.2-9 Parma Polyhedra Library (runtime l
ii zlib1g 1: compression library - runtime

Versions of packages gcc-4.5 recommends:
ii libc6-dev 2.11.2-7 Embedded GNU C Library: Developmen

Versions of packages gcc-4.5 suggests:
pn binutils-gold <none> (no description available)
pn gcc-4.5-doc <none> (no description available)
pn gcc-4.5-locales <none> (no description available)
ii gcc-4.5-multilib 4.5.1-9 The GNU C compiler (multilib files
pn libgcc1-dbg <none> (no description available)
pn libgomp1-dbg <none> (no description available)
ii libmudflap0-4.5-dev 4.5.1-9 GCC mudflap support libraries (dev
pn libmudflap0-dbg <none> (no description available)

-- no debconf information

brian m. carlson / brian with sandals: Houston, Texas, US
+1 832 623 2791 | http://www.crustytoothpaste.net/~bmc | My opinion only
OpenPGP: RSA v4 4096b: 88AC E9B2 9196 305B A994 7552 F1BA 225C 0223 B187

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