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Support for architectures without hardware interlocks
- From: David Kang <dkang at isi dot edu>
- To: gcc at gcc dot gnu dot org
- Date: Fri, 31 Oct 2014 12:03:29 -0700 (PDT)
- Subject: Support for architectures without hardware interlocks
- Authentication-results: sourceware.org; auth=none
I'm working on porting gcc to an architecture without hardware interlock support for floating point unit. I read that instruction latency time can be expressed in machine description file of gcc. I set the latency time of the instructions and built gcc.
I expected that gcc would put the two dependent instructions apart automatically
at least as many as the latency time of the first instruction.
However, my gcc doesn't do that.
I'm using a little old 4.7.3.
I also expected that gcc may fill the gap with no-op when it cannot find
other useful instructions to fill the gap.
But, I don't see that, either.
Does gcc support an architecture without hardware interlock automatically?
Could anyone help me to understand how I can enforce the latency requirements
of two dependent instructions in gcc?
I saw that GCC didn't support architectures without hardware interlocks in the gcc mailing list
which is dated in 2007. (https://gcc.gnu.org/ml/gcc/2007-07/msg00915.html)
Is it still true?
Dr. Dong-In "David" Kang