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Mail Archives: djgpp/2000/04/10/12:55:14

From: "Alexei A. Frounze" <alex DOT fru AT mtu-net DOT ru>
Newsgroups: comp.os.msdos.djgpp
Subject: inefficiency of GCC output code & -O problem
Date: Mon, 10 Apr 2000 21:25:14 +0400
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hi!

1st question...

Why GCC output too much redundant code? 
I mean, it always put values to the CPU registers, although it's possible to
make the same operation w/o taking registers?

Also why GCC does type cast of byte/word <-> dword values so awful? It allocates
some extra bytes on the stack, put values there and get them back...

Is it a normal thing, if one instruction that adds something to ESP(or EBP) is
followed by sutracting instruction that works with the same register?

... I'll find some extra info later ...

2nd question...

Why the "-O2" switch works normally for pure C source code and makes compiler
failing on the source with inline assembly (in the .S file made out of such .C
an error encounters: 
"Error: Error: Missing ')' assumed" 
"Error: Error: Ignoring junk `(%ebp))' after expression")? 
W/o the -O2 switch it's compiled fine. Isn't it a little bit strange?


Thanks in advance.
Alexei A. Frounze
-----------------------------------------
Homepage: http://alexfru.chat.ru
Mirror:   http://members.xoom.com/alexfru

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