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Re: [PATCH, ira] handle all fixed register classes

Jim Wilson wrote:
This is the rest of the solution for PR43520.  The IA-64 port has some
register classes in which all of the registers are fixed.  The
scheduling reg pressure code in ira sees that we have a class with 0
allocatable registers and decides to add extra dependencies to prevent
increasing register pressure.  But if we have no allocatable registers,
then we can't possibly have a register pressure problem.  So ira should
be ignoring classes with no allocatable registers.

This patch was tested with an ia64-linux C and C++ bootstrap and make
check.  I also verified by hand that is solves the original problem.

I also tested this with an x86-linux bootstrap (all default languages)
and make check.  There were no regressions.  I did this with an extra
line added
  ira_assert (ira_available_class_regs[cl] != 0);
The assert never triggered showing that this patch has no effect on
32-bit x86-linux code.


This is ok, Jim. Thanks a lot for working on this problem.

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