Bug 593064 - Out of CLOBBERED_REGS with inline assembly
Out of CLOBBERED_REGS with inline assembly
Product: Fedora
Classification: Fedora
Component: gcc (Show other bugs)
All Linux
low Severity medium
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Assigned To: Jakub Jelinek
Fedora Extras Quality Assurance
: Reopened
Depends On:
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Reported: 2010-05-17 14:22 EDT by Lubomir Rintel
Modified: 2011-06-27 12:26 EDT (History)
1 user (show)

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Fixed In Version:
Doc Type: Bug Fix
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Last Closed: 2011-06-27 12:26:27 EDT
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Description Lubomir Rintel 2010-05-17 14:22:55 EDT

  int func0 (...);
  int func1 (void);
  func3 (void)
          unsigned var;
          __asm__ (
                  "" :
                  "=a" (var),
                  "=c" (var),
                  "=d" (var),
                  "=r" (var)
          func0 (
                  func1 (),
                  func1 (),
                  func1 (),
                  func1 (),
                  (var >> 8) & 0xff

$ g++ -fPIC -c -O2 repr.cpp 
repr.cpp: In function ‘void func3()’:
repr.cpp:15: error: can't find a register in class ‘CLOBBERED_REGS’ while reloading ‘asm’
repr.cpp:15: error: ‘asm’ operand has impossible constraints

Version-Release number of selected component (if applicable):


Additional info:

I've not been able to pin the problem to a specific optimization -- enabling all of "g++ -c -Q -O2 --help=optimizers" does not exhibit the problem.
Comment 1 Jakub Jelinek 2010-05-17 14:30:01 EDT
This is invalid.  You can't use the same var for more than one output operand.
Comment 2 Lubomir Rintel 2010-05-17 15:08:08 EDT
Sorry, sense was lost somewhere in the attempts to create a minimal testcase. Here's another one:

  int func0 (...);
  int func1 (void);
  func3 (void)
          unsigned var1, var2, var3, var4;
          __asm__ (
                  "" :
                  "=a" (var1),
                  "=d" (var3),
                  "=c" (var2),
                  "=r" (var4)
          func0 (
                  func1 (),
                  func1 (),
                  func1 (),
                  func1 (),
                  (var4 >> 8) & 0xff
Comment 3 Bug Zapper 2011-06-02 09:54:26 EDT
This message is a reminder that Fedora 13 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
and issuing updates for Fedora 13.  It is Fedora's policy to close all
bug reports from releases that are no longer maintained.  At that time
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Comment 4 Bug Zapper 2011-06-27 12:26:27 EDT
Fedora 13 changed to end-of-life (EOL) status on 2011-06-25. Fedora 13 is 
no longer maintained, which means that it will not receive any further 
security or bug fix updates. As a result we are closing this bug.

If you can reproduce this bug against a currently maintained version of 
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