[Mesa-dev] [PATCH 2/2] radeonsi: Allow dumping LLVM IR before optimization passes

[Nicolai Hähnle]

On 04.02.2016 13:52, Tom Stellard wrote:
> On Thu, Feb 04, 2016 at 09:15:26AM +0100, Nicolai Hähnle wrote:
>> From: Nicolai Hähnle <nicolai.haehnle at amd.com>
>>
>> Set R600_DEBUG=preoptir to dump the LLVM IR before optimization passes,
>> to allow diagnosing problems caused by optimization passes.
>>
>> Note that in order to compile the resulting IR with llc, you will first
>> have to run at least the mem2reg pass, e.g.
>>
>> opt -mem2reg -S < shader.ll | llc -march=amdgcn -mcpu=bonaire
>>
>> Signed-off-by: Michel Dänzer <michel.daenzer at amd.com> (original patch)
>> Signed-off-by: Nicolai Hähnle <nicolai.haehnle at amd.com> (w/ debug flag)
>> ---
>> Having the option is a good idea, but I prefer to have a separate debug
>> flag for it so that when you try to analyze bugs in codegen (which in
>> my experience happens more often) you don't have to worry about
>> replicating the exact same sequence of optimizations manually via the
>> command line to reproduce the problem there.
>>
>>   src/gallium/drivers/radeon/r600_pipe_common.c |  1 +
>>   src/gallium/drivers/radeon/r600_pipe_common.h |  1 +
>>   src/gallium/drivers/radeonsi/si_shader.c      | 16 ++++++++++++++--
>>   3 files changed, 16 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/gallium/drivers/radeon/r600_pipe_common.c b/src/gallium/drivers/radeon/r600_pipe_common.c
>> index c827dbd..a1432ed 100644
>> --- a/src/gallium/drivers/radeon/r600_pipe_common.c
>> +++ b/src/gallium/drivers/radeon/r600_pipe_common.c
>> @@ -393,6 +393,7 @@ static const struct debug_named_value common_debug_options[] = {
>>   	{ "noir", DBG_NO_IR, "Don't print the LLVM IR"},
>>   	{ "notgsi", DBG_NO_TGSI, "Don't print the TGSI"},
>>   	{ "noasm", DBG_NO_ASM, "Don't print disassembled shaders"},
>> +	{ "preoptir", DBG_PREOPT_IR, "Print the LLVM IR before initial optimizations" },
>>
>>   	/* features */
>>   	{ "nodma", DBG_NO_ASYNC_DMA, "Disable asynchronous DMA" },
>> diff --git a/src/gallium/drivers/radeon/r600_pipe_common.h b/src/gallium/drivers/radeon/r600_pipe_common.h
>> index c7e4c44..4e36631 100644
>> --- a/src/gallium/drivers/radeon/r600_pipe_common.h
>> +++ b/src/gallium/drivers/radeon/r600_pipe_common.h
>> @@ -71,6 +71,7 @@
>>   #define DBG_NO_IR		(1 << 12)
>>   #define DBG_NO_TGSI		(1 << 13)
>>   #define DBG_NO_ASM		(1 << 14)
>> +#define DBG_PREOPT_IR		(1 << 15)
>>   /* Bits 21-31 are reserved for the r600g driver. */
>>   /* features */
>>   #define DBG_NO_ASYNC_DMA	(1llu << 32)
>> diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
>> index 8b524cf..d9ed6b2 100644
>> --- a/src/gallium/drivers/radeonsi/si_shader.c
>> +++ b/src/gallium/drivers/radeonsi/si_shader.c
>> @@ -4092,7 +4092,7 @@ int si_compile_llvm(struct si_screen *sscreen,
>>   	if (r600_can_dump_shader(&sscreen->b, processor)) {
>>   		fprintf(stderr, "radeonsi: Compiling shader %d\n", count);
>>
>> -		if (!(sscreen->b.debug_flags & DBG_NO_IR))
>> +		if (!(sscreen->b.debug_flags & (DBG_NO_IR | DBG_PREOPT_IR)))
>>   			LLVMDumpModule(mod);
>>   	}
>>
>> @@ -4178,6 +4178,12 @@ static int si_generate_gs_copy_shader(struct si_screen *sscreen,
>>   	si_llvm_export_vs(bld_base, outputs, gsinfo->num_outputs);
>>
>>   	LLVMBuildRetVoid(bld_base->base.gallivm->builder);
>> +
>> +	/* Dump LLVM IR before any optimization passes */
>> +	if (sscreen->b.debug_flags & DBG_PREOPT_IR &&
>> +	    r600_can_dump_shader(&sscreen->b, TGSI_PROCESSOR_GEOMETRY))
>> +		LLVMDumpModule(bld_base->base.gallivm->module);
>> +
>>   	radeon_llvm_finalize_module(&si_shader_ctx->radeon_bld);
>>
>>   	if (dump)
>> @@ -4385,9 +4391,15 @@ int si_shader_create(struct si_screen *sscreen, LLVMTargetMachineRef tm,
>>   	}
>>
>>   	LLVMBuildRetVoid(bld_base->base.gallivm->builder);
>> +	mod = bld_base->base.gallivm->module;
>> +
>> +	/* Dump LLVM IR before any optimization passes */
>> +	if (sscreen->b.debug_flags & DBG_PREOPT_IR &&
>> +	    r600_can_dump_shader(&sscreen->b, si_shader_ctx.type))
>> +		LLVMDumpModule(mod);
>> +
>
> Is there any reason not to add the dump in  radeon_llvm_finalize_module()
> after PromoteMem2Reg has run?  This would make the output readable by llc
> and then you would only need to add the dump call in one place.

In addition to Michel's observation, that's not really possible anyway 
because all the passes are run at once from LLVMRunFunctionPassManager, 
the functions before just set things up.

I did consider doing the dump from radeon_llvm_finalize_module, but the 
function doesn't have (and probably shouldn't have) the information 
needed to make the decision whether to dump or not, so IMO it's cleaner 
this way.

Cheers,
Nicolai

>
> -Tom
>
>>   	radeon_llvm_finalize_module(&si_shader_ctx.radeon_bld);
>>
>> -	mod = bld_base->base.gallivm->module;
>>   	r = si_compile_llvm(sscreen, &shader->binary, &shader->config, tm,
>>   			    mod, debug, si_shader_ctx.type);
>>   	if (r) {
>> --
>> 2.5.0
>>
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