[Mesa-dev] [PATCH 4/4] gallivm: dump bitcode before optimization

[Jose Fonseca]

On 23/04/18 05:24, sroland at vmware.com wrote:
> From: Roland Scheidegger <sroland at vmware.com>
> 
> If we dump the bitcode for off-line debug purposes, we really want the
> pre-optimized bitcode, otherwise it's useless in identifying problems
> with IR optimization (if you have a shader which takes an hour to do
> IR optimization, it's also nice you don't have to wait that hour...).
> Also, print out the function passes for opt which correspond to what
> was used for jit compilation (and also the opt level for codegen).
> Using opt/llc this way should then pretty much mimic what was done
> for jit. (When specifying something like -time-passes
> -debug-pass=[Structure|Arguments] (for either opt or llc) that also
> gives very useful information in which passes all the time was spent,
> and which passes are really run along with the order - llvm will add
> passes due to dependencies on its own, and of course -O2 for llc
> comes with a ~100 pass list.)
> ---
>   src/gallium/auxiliary/gallivm/lp_bld_init.c | 35 +++++++++++++++++------------
>   1 file changed, 21 insertions(+), 14 deletions(-)
> 
> diff --git a/src/gallium/auxiliary/gallivm/lp_bld_init.c b/src/gallium/auxiliary/gallivm/lp_bld_init.c
> index d0afff1..41d828c 100644
> --- a/src/gallium/auxiliary/gallivm/lp_bld_init.c
> +++ b/src/gallium/auxiliary/gallivm/lp_bld_init.c
> @@ -142,6 +142,10 @@ create_pass_manager(struct gallivm_state *gallivm)
>          * TODO: Evaluate passes some more - keeping in mind
>          * both quality of generated code and compile times.
>          */
> +      /*
> +       * NOTE: if you change this, don't forget to change the output
> +       * with GALLIVM_DEBUG_DUMP_BC in gallivm_compile_module.
> +       */
>         LLVMAddScalarReplAggregatesPass(gallivm->passmgr);
>         LLVMAddEarlyCSEPass(gallivm->passmgr);
>         LLVMAddCFGSimplificationPass(gallivm->passmgr);
> @@ -151,7 +155,7 @@ create_pass_manager(struct gallivm_state *gallivm)
>          * due to licm implying lcssa (since llvm 3.5), which can take forever.
>          * Even for sane shaders, the cost of licm is rather high (and not just
>          * due to lcssa, licm itself too), though mostly only in cases when it
> -       * can actually move things, so having to disable it is a pity.
> +       * can actually move things, so having to disable it is a pity.
>          * LLVMAddLICMPass(gallivm->passmgr);
>          */
>         LLVMAddReassociatePass(gallivm->passmgr);
> @@ -597,6 +601,22 @@ gallivm_compile_module(struct gallivm_state *gallivm)
>         gallivm->builder = NULL;
>      }
>   
> +   /* Dump bitcode to a file */
> +   if (gallivm_debug & GALLIVM_DEBUG_DUMP_BC) {
> +      char filename[256];
> +      assert(gallivm->module_name);
> +      util_snprintf(filename, sizeof(filename), "ir_%s.bc", gallivm->module_name);
> +      LLVMWriteBitcodeToFile(gallivm->module, filename);
> +      debug_printf("%s written\n", filename);
> +      debug_printf("Invoke as \"opt %s %s | llc -O%d %s%s\"\n",
> +                   gallivm_debug & GALLIVM_DEBUG_NO_OPT ? "-mem2reg" :
> +                   "-sroa -early-cse -simplifycfg -reassociate "
> +                   "-mem2reg -constprop -instcombine -gvn",
> +                   filename, gallivm_debug & GALLIVM_DEBUG_NO_OPT ? 0 : 2,
> +                   (HAVE_LLVM >= 0x0305) ? "[-mcpu=<-mcpu option>] " : "",
> +                   "[-mattr=<-mattr option(s)>]");
> +   }
> +
>      if (gallivm_debug & GALLIVM_DEBUG_PERF)
>         time_begin = os_time_get();
>   
> @@ -630,19 +650,6 @@ gallivm_compile_module(struct gallivm_state *gallivm)
>                      gallivm->module_name, time_msec);
>      }
>   
> -   /* Dump byte code to a file */
> -   if (gallivm_debug & GALLIVM_DEBUG_DUMP_BC) {
> -      char filename[256];
> -      assert(gallivm->module_name);
> -      util_snprintf(filename, sizeof(filename), "ir_%s.bc", gallivm->module_name);
> -      LLVMWriteBitcodeToFile(gallivm->module, filename);
> -      debug_printf("%s written\n", filename);
> -      debug_printf("Invoke as \"llc %s%s -o - %s\"\n",
> -                   (HAVE_LLVM >= 0x0305) ? "[-mcpu=<-mcpu option>] " : "",
> -                   "[-mattr=<-mattr option(s)>]",
> -                   filename);
> -   }
> -
>      if (use_mcjit) {
>         /* Setting the module's DataLayout to an empty string will cause the
>          * ExecutionEngine to copy to the DataLayout string from its target
> 

Series looks good to me.

Reviewed-by: Jose Fonseca <jfonseca at vmware.com>