[llvm] constant_fold_fabs unreachable

[aaronmondal]

Tablegen raises the following errors for AMDGPUISel.td and AArch64.td on recent main (75632fe).

INFO: From Generating code from table: lib/Target/AMDGPU/AMDGPUGISel.td @llvm-project-overlay~17-init-bcr.3~llvm_project_overlay~llvm-project//llvm:amdgpu_isel_target_gen__ge
n_global_isel_combiner__combiners_AMDGPUPostLegalizerCombinerHelper_genrule:
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched
INFO: From Generating code from table: lib/Target/AMDGPU/AMDGPUGISel.td @llvm-project-overlay~17-init-bcr.3~llvm_project_overlay~llvm-project//llvm:amdgpu_isel_target_gen__ge
n_global_isel_combiner__combiners_AMDGPUPreLegalizerCombinerHelper_genrule:
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched
INFO: From Generating code from table: lib/Target/AArch64/AArch64.td @llvm-project-overlay~17-init-bcr.3~llvm_project_overlay~llvm-project//llvm:AArch64CommonTableGen__gen_gl
obal_isel_combiner__combiners_AArch64PreLegalizerCombinerHelper_genrule:
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched
error: Leaf constant_fold_fabs is unreachable
note: Leaf idempotent_prop will have already matched

cc @arsenm

[arsenm]

The message is harmless. It's wrong to be diagnosing anything since the generated matcher is not actually hidden. It also shouldn't say "error" for something non-fatal which exits successfully

[RKSimon]

      else if (FullyTestedLeafI != Leaves.end()) {
        PrintError("Leaf " + LeafI->getName() + " is unreachable");
        PrintNote("Leaf " + FullyTestedLeafI->getName() +
                  " will have already matched");
      }

So should that PrintError be made a PrintNote?

[fhahn]

Is it possible to fix those notes as well, to keep the build logs clean?

[arsenm]

So should that PrintError be made a PrintNote?

Maybe PrintWarning?

Is it possible to fix those notes as well, to keep the build logs clean?

Theoretically but I haven't spent any time looking at this. Could just comment it out?

[aemerson]

@arsenm could you fix this?

[aemerson]

I'm just going to delete the code complaining since it's not correct.