[PATCH] Statepoint infrastructure for garbage collection

Andrew Trick atrick at apple.com
Wed Nov 5 18:00:01 PST 2014


> On Nov 5, 2014, at 5:28 PM, Philip Reames <listmail at philipreames.com> wrote:
> 
> ================
> Comment at: include/llvm/CodeGen/MachineInstr.h:91
> @@ -90,3 +90,3 @@
> 
> -  uint8_t NumMemRefs;                   // Information on memory references.
> +  uint16_t NumMemRefs;                  // Information on memory references.
>   mmo_iterator MemRefs;
> ----------------
> ributzka wrote:
>> Are you really hitting the limitations of uint8_t for mem references? Changing this by one byte increases the overall size of a MachineInstr from 64 bytes to 72 bytes (due to padding).
> We were at one point.  I'm not sure we still are.  I'm fine removing this in the change which initially gets upstreamed and revisiting this separately.  

Good, thanks. A lot of careful engineering went into packing MachineInstr into 64 bytes in order to squeeze compile time out of backend passes. And we still get complaints that machine code is too slow to generate. If we need more MemRefs, we’ll have to come up with another way to get them.

-Andy
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