AMDGPU/SI: Don't run SLSR and NaryReassociate passes

[• tstellarAMD]

Summary

These can cause infinite compile times like for example:
https://llvm.org/bugs/show_bug.cgi?id=28721

[arsenm]

The bug should be fixed instead of this. However I noticed this is run for -O0 which should be fixed

[• tstellarAMD]

In D24098#530742, @arsenm wrote:

The bug should be fixed instead of this. However I noticed this is run for -O0 which should be fixed

I agree, but these bugs are preventing us from being able to compiler some programs, and I'm not sure when someone will be able to look into fixing this bug.

[arsenm]

The bug should be fixed instead of this. However I noticed this is run for -O0 which should be fixed

In D24098#530751, @tstellarAMD wrote:

In D24098#530742, @arsenm wrote:

The bug should be fixed instead of this. However I noticed this is run for -O0 which should be fixed

I agree, but these bugs are preventing us from being able to compiler some programs, and I'm not sure when someone will be able to look into fixing this bug.

With just ripping this out, it's more likely that nobody will ever get around to re-enabling these. How about just adding a flag to allow disabling this so those programs can work around it for now? Alternatively this bug should be higher priority

lib/Target/AMDGPU/AMDGPUTargetMachine.cpp

if (getOptLevel() == CodeGenOpt::Aggressive)
     addPass(createGVNPass());
   else
     addPass(createEarlyCSEPass());
 }
 
 void AMDGPUPassConfig::addStraightLineScalarOptimizationPasses() {
   addPass(createSeparateConstOffsetFromGEPPass());
   addPass(createSpeculativeExecutionPass());
-  // ReassociateGEPs exposes more opportunites for SLSR. See
-  // the example in reassociate-geps-and-slsr.ll.
-  addPass(createStraightLineStrengthReducePass());
   // SeparateConstOffsetFromGEP and SLSR creates common expressions which GVN or
   // EarlyCSE can reuse.
   addEarlyCSEOrGVNPass();
-  // Run NaryReassociate after EarlyCSE/GVN to be more effective.
-  addPass(createNaryReassociatePass());
-  // NaryReassociate on GEPs creates redundant common expressions, so run
-  // EarlyCSE after it.
-  addPass(createEarlyCSEPass());
 }
 
 void AMDGPUPassConfig::addIRPasses() {
   // There is no reason to run these.
   disablePass(&StackMapLivenessID);
   disablePass(&FuncletLayoutID);
   disablePass(&PatchableFunctionID);