[Mesa-dev] [PATCH 05/19] i965/fs: Loop from 0 to inst->sources, not 0 to 3.

[Ian Romanick]

On 05/31/2014 10:11 PM, Kenneth Graunke wrote:
> On Tuesday, May 27, 2014 06:47:36 PM Matt Turner wrote:
> [snip]
>> diff --git a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp 
> b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
>> index 069b60f..a1aff21 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs_copy_propagation.cpp
>> @@ -353,7 +353,7 @@ fs_visitor::try_constant_propagate(fs_inst *inst, 
> acp_entry *entry)
>>     if (entry->src.file != IMM)
>>        return false;
>>  
>> -   for (int i = 2; i >= 0; i--) {
>> +   for (int i = inst->sources - 1; i >= 0; i--) {
>>        if (inst->src[i].file != entry->dst.file ||
>>            inst->src[i].reg != entry->dst.reg ||
>>            inst->src[i].reg_offset != entry->dst.reg_offset ||
> 
> I am glad to see that you're using a signed integer type here.  For 
> BRW_OPCODE_NOP, SHADER_OPCODE_PLACEHOLDER_HALT, and so on, inst->sources could 
> conceievably be 0.  (Today, you set it to 3 for some reason, but I could see 
> someone coming along and "fixing" that later...)
> 
> If you had used unsigned types, this would translate into i = 4294967296; i >= 
> 0; i--, which would take forever.  With signed types, it works, and no one 
> should get bitten by that bug.

Consistency of types is good.  Some folks build with additional
warnings, and the flood of

main/bufferobj.c:2855:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]

can hide legit bugs. :(

> Patches 1-8 are:
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
> (and you can ignore my comment on patch 4 - I'm happy to see that done in 
> later patches - no need to block this any further on trivialities)
> 
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev


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