[Mesa-dev] [PATCH] radv: run the EarlyCSEMemSSA LLVM pass

[Samuel Pitoiset]

On 05/24/2018 11:00 PM, Tom Stellard wrote:
> On 05/24/2018 01:55 PM, Samuel Pitoiset wrote:
>> It's recommended by the instruction combining pass, and
>> RadeonSI also runs it.
>>
>> This pass used to segfault with one shader of F12017 but it
>> has been fixed somewhere in LLVM 7.
>>
> 
> Do you know which patch fixes this?  Or do you have an LLVM IR test
> for this?

I don't know. Maybe the LLVM IR generated by RADV changed too and it 
longer happens because of that.

The LLVM IR test case was here https://reviews.llvm.org/D35073#998707

Unfortunately, hastebin links are dead. :/

I will try to reproduce with LLVM 6.

> 
> -Tom
> 
>> Polaris10:
>> Totals from affected shaders:
>> SGPRS: 441352 -> 441648 (0.07 %)
>> VGPRS: 310888 -> 300784 (-3.25 %)
>> Spilled SGPRs: 13576 -> 12983 (-4.37 %)
>> Code Size: 22560328 -> 22420544 (-0.62 %) bytes
>> Max Waves: 40755 -> 41366 (1.50 %)
>>
>> Vega10:
>> Totals from affected shaders:
>> SGPRS: 442848 -> 442000 (-0.19 %)
>> VGPRS: 310396 -> 300460 (-3.20 %)
>> Spilled SGPRs: 13708 -> 12906 (-5.85 %)
>> Code Size: 22479428 -> 22336216 (-0.64 %) bytes
>> Max Waves: 45783 -> 46506 (1.58 %)
>>
>> Signed-off-by: Samuel Pitoiset <samuel.pitoiset at gmail.com>
>> ---
>>   src/amd/vulkan/radv_nir_to_llvm.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/src/amd/vulkan/radv_nir_to_llvm.c b/src/amd/vulkan/radv_nir_to_llvm.c
>> index b174c027d9..d89c22ea06 100644
>> --- a/src/amd/vulkan/radv_nir_to_llvm.c
>> +++ b/src/amd/vulkan/radv_nir_to_llvm.c
>> @@ -2982,6 +2982,12 @@ static void ac_llvm_finalize_module(struct radv_shader_context *ctx)
>>   	LLVMAddLICMPass(passmgr);
>>   	LLVMAddAggressiveDCEPass(passmgr);
>>   	LLVMAddCFGSimplificationPass(passmgr);
>> +#if HAVE_LLVM >= 0x0700
>> +	/* XXX: This LLVM pass used to segfault with one shader of F12017. This
>> +	 * has been fixed somewhere in LLVM 7. */
>> +	/* This is recommended by the instruction combining pass. */
>> +	LLVMAddEarlyCSEMemSSAPass(passmgr);
>> +#endif
>>   	LLVMAddInstructionCombiningPass(passmgr);
>>   
>>   	/* Run the pass */
>>
>