[WIP][AArch64TargetMachine] Improve codegenprep for agressive mode

[djtodoro]

Summary

This improves the AArch64 Target Machine, since the SeparateConstOffsetFromGEP is being run.

TODO: Get the data on SPEC benchmark.

Co-authored-by: @mmatic05, @milica-lazarevic, @dmilosevic141

[SjoerdMeijer]

I can run SPEC. Can you add a test case, a reproducer, where we want to see improved codegen as a result of this?

[djtodoro]

In D113285#3114919, @SjoerdMeijer wrote:

I can run SPEC. Can you add a test case, a reproducer, where we want to see improved codegen as a result of this?

Thanks for that!

Can you add a test case, a reproducer, where we want to see improved codegen as a result of this?

Sure. I'll need to add tests to all patches from the stack, that is the reason it is marked as WIP.

llvm/lib/Target/AArch64/AArch64TargetMachine.cpp

 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Transforms/CFGuard.h"
+#include "llvm/Transforms/Scalar/GVN.h"
 #include "llvm/Transforms/Scalar.h"
 #include <memory>
 #include <string>
 
 using namespace llvm;
 
 static cl::opt<bool> EnableCCMP("aarch64-enable-ccmp",
                                 cl::desc("Enable the CCMP formation pass"),
if (TM->getOptLevel() != CodeGenOpt::None) {
     addPass(createInterleavedAccessPass());
   }
 
   if (TM->getOptLevel() == CodeGenOpt::Aggressive && EnableGEPOpt) {
     // Call SeparateConstOffsetFromGEP pass to extract constants within indices
     // and lower a GEP with multiple indices to either arithmetic operations or
     // multiple GEPs with single index.
     addPass(createSeparateConstOffsetFromGEPPass(true));
+    addPass(createStraightLineStrengthReducePass());
+    // SeparateConstOffsetFromGEP and SLSR creates common expressions which GVN
+    // can optimize.
+    addPass(createGVNPass());
+    addPass(createNaryReassociatePass());
     // Call EarlyCSE pass to find and remove subexpressions in the lowered
     // result.
     addPass(createEarlyCSEPass());
     // Do loop invariant code motion in case part of the lowered result is
     // invariant.
     addPass(createLICMPass());
   }
 

llvm/test/CodeGen/AArch64/O3-pipeline.ll

 ; CHECK-NEXT:       Function Alias Analysis Results
 ; CHECK-NEXT:       Memory SSA
 ; CHECK-NEXT:       Interleaved Load Combine Pass
 ; CHECK-NEXT:       Dominator Tree Construction
 ; CHECK-NEXT:       Interleaved Access Pass
 ; CHECK-NEXT:       Natural Loop Information
 ; CHECK-NEXT:      Scalar Evolution Analysis
 ; CHECK-NEXT:      Split GEPs to a variadic base and a constant offset for better CSE
+; CHECK-NEXT:      Scalar Evolution Analysis
+; CHECK-NEXT:      Straight line strength reduction
+; CHECK-NEXT:      Phi Values Analysis
+; CHECK-NEXT:      Basic Alias Analysis (stateless AA impl)
+; CHECK-NEXT:      Function Alias Analysis Results
+; CHECK-NEXT:      Memory Dependence Analysis
+; CHECK-NEXT:      Lazy Branch Probability Analysis
+; CHECK-NEXT:      Lazy Block Frequency Analysis
+; CHECK-NEXT:      Optimization Remark Emitter
+; CHECK-NEXT:      Global Value Numbering
+; CHECK-NEXT:      Scalar Evolution Analysis
+; CHECK-NEXT:      Nary reassociation
 ; CHECK-NEXT:      Early CSE
 ; CHECK-NEXT:      Basic Alias Analysis (stateless AA impl)
 ; CHECK-NEXT:      Function Alias Analysis Results
 ; CHECK-NEXT:      Memory SSA
 ; CHECK-NEXT:      Canonicalize natural loops
 ; CHECK-NEXT:      LCSSA Verifier
 ; CHECK-NEXT:      Loop-Closed SSA Form Pass
 ; CHECK-NEXT:      Scalar Evolution Analysis