c/7344: performance regression on huge case statements

[Robert Schiele]

The following reply was made to PR c/7344; it has been noted by GNATS.

From: Robert Schiele <rschiele@uni-mannheim.de>
To: Nathanael Nerode <neroden@twcny.rr.com>
Cc: gcc-gnats@gcc.gnu.org, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org
Subject: Re: c/7344: performance regression on huge case statements
Date: Thu, 17 Oct 2002 15:41:53 +0200

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 On Thu, Oct 17, 2002 at 08:59:26AM -0400, Nathanael Nerode wrote:
 > What should we do for a test case here?  I feel that it should have one,
 > but the minimal testcase is *inherently* 239K, so I'm not quite sure=20
 > what to do here.
 
 Hmm, we can do this testcase with the following short code:
 
 ---
 #define CL0(a) case a: f(); goto c;
 #define CL1(a) CL0(a##0) CL0(a##1) CL0(a##2) CL0(a##3) CL0(a##4) CL0(a##5) =
 CL0(a##6) CL0(a##7) CL0(a##8) CL0(a##9)
 #define CL2(a) CL1(a##0) CL1(a##1) CL1(a##2) CL1(a##3) CL1(a##4) CL1(a##5) =
 CL1(a##6) CL1(a##7) CL1(a##8) CL1(a##9)
 #define CL3(a) CL2(a##0) CL2(a##1) CL2(a##2) CL2(a##3) CL2(a##4) CL2(a##5) =
 CL2(a##6) CL2(a##7) CL2(a##8) CL2(a##9)
 #define CL4(a) CL3(a##0) CL3(a##1) CL3(a##2) CL3(a##3) CL3(a##4) CL3(a##5) =
 CL3(a##6) CL3(a##7) CL3(a##8) CL3(a##9)
 
 void f();
 
 void a() {
     int b;
  c: switch (b) {
         CL4(1)
     }
 }
 ---
 
 Robert
 
 --=20
 Robert Schiele			Tel.: +49-621-181-2517
 Dipl.-Wirtsch.informatiker	mailto:rschiele@uni-mannheim.de
 
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