[PATCH] D104099: [NewPM] Remove SpeculateAroundPHIs pass from pipeline

[Roman Lebedev via Phabricator via cfe-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: thopre, bjope, nikic, chandlerc, aeubanks.
lebedev.ri added a project: LLVM.
Herald added subscribers: ormris, wenlei, steven_wu, hiraditya.
lebedev.ri requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

Addition of this pass has been botchered.
There is no particular reason why it had to be sold as an inseparable part of new-pm transition.
It was added when old-pm was still the default, and very *very* few users were actually tracking new-pm,
so it's effects weren't measured. Which means, some of the turnoil of the new-pm transition
are actually likely regressions due to this pass.

Likewise, there has been a number of post-commit feedback (post new-pm switch), namely

- https://reviews.llvm.org/D37467#2787157 (regresses HW-loops)
- https://reviews.llvm.org/D37467#2787259 (should not be in middle-end, should run after LSR, not before)
- https://reviews.llvm.org/D95789 ()

and in the half year past, the pass authors (google) still haven't found time to respond to any of that.

Hereby it is proposed to backout the patch from the pipeline, until someone who cares about it
can address the issues reported, and properly start the process
of adding a new pass into the pipeline, with proper performance evaluation.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104099

Files:
  clang/test/CodeGen/thinlto-distributed-newpm.ll
  llvm/lib/Passes/PassBuilder.cpp
  llvm/test/Other/new-pm-defaults.ll
  llvm/test/Other/new-pm-thinlto-defaults.ll
  llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
  llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll


Index: llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
@@ -199,7 +199,6 @@
 ; CHECK-O-NEXT: Running pass: InstSimplifyPass
 ; CHECK-O-NEXT: Running pass: DivRemPairsPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
-; CHECK-O-NEXT: Running pass: SpeculateAroundPHIsPass
 ; CHECK-O-NEXT: Running pass: CGProfilePass
 ; CHECK-O-NEXT: Running pass: GlobalDCEPass
 ; CHECK-O-NEXT: Running pass: ConstantMergePass
Index: llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
@@ -187,7 +187,6 @@
 ; CHECK-O-NEXT: Running pass: InstSimplifyPass
 ; CHECK-O-NEXT: Running pass: DivRemPairsPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
-; CHECK-O-NEXT: Running pass: SpeculateAroundPHIsPass
 ; CHECK-O-NEXT: Running pass: CGProfilePass
 ; CHECK-O-NEXT: Running pass: GlobalDCEPass
 ; CHECK-O-NEXT: Running pass: ConstantMergePass
Index: llvm/test/Other/new-pm-thinlto-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-thinlto-defaults.ll
+++ llvm/test/Other/new-pm-thinlto-defaults.ll
@@ -218,7 +218,6 @@
 ; CHECK-POSTLINK-O-NEXT: Running pass: InstSimplifyPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: DivRemPairsPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: SimplifyCFGPass
-; CHECK-POSTLINK-O-NEXT: Running pass: SpeculateAroundPHIsPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: CGProfilePass
 ; CHECK-POSTLINK-O-NEXT: Running pass: GlobalDCEPass
 ; CHECK-POSTLINK-O-NEXT: Running pass: ConstantMergePass
Index: llvm/test/Other/new-pm-defaults.ll
===================================================================
--- llvm/test/Other/new-pm-defaults.ll
+++ llvm/test/Other/new-pm-defaults.ll
@@ -237,7 +237,6 @@
 ; CHECK-O-NEXT: Running pass: InstSimplifyPass
 ; CHECK-O-NEXT: Running pass: DivRemPairsPass
 ; CHECK-O-NEXT: Running pass: SimplifyCFGPass
-; CHECK-O-NEXT: Running pass: SpeculateAroundPHIsPass
 ; CHECK-EP-OPTIMIZER-LAST: Running pass: NoOpFunctionPass
 ; CHECK-O-NEXT: Running pass: CGProfilePass
 ; CHECK-O-NEXT: Running pass: GlobalDCEPass
Index: llvm/lib/Passes/PassBuilder.cpp
===================================================================
--- llvm/lib/Passes/PassBuilder.cpp
+++ llvm/lib/Passes/PassBuilder.cpp
@@ -1443,11 +1443,6 @@
   // resulted in single-entry-single-exit or empty blocks. Clean up the CFG.
   OptimizePM.addPass(SimplifyCFGPass());
 
-  // Optimize PHIs by speculating around them when profitable. Note that this
-  // pass needs to be run after any PRE or similar pass as it is essentially
-  // inserting redundancies into the program. This even includes SimplifyCFG.
-  OptimizePM.addPass(SpeculateAroundPHIsPass());
-
   if (PTO.Coroutines)
     OptimizePM.addPass(CoroCleanupPass());
 
Index: clang/test/CodeGen/thinlto-distributed-newpm.ll
===================================================================
--- clang/test/CodeGen/thinlto-distributed-newpm.ll
+++ clang/test/CodeGen/thinlto-distributed-newpm.ll
@@ -165,7 +165,6 @@
 ; CHECK-O: Running pass: InstSimplifyPass on main
 ; CHECK-O: Running pass: DivRemPairsPass on main
 ; CHECK-O: Running pass: SimplifyCFGPass on main
-; CHECK-O: Running pass: SpeculateAroundPHIsPass on main
 ; CHECK-O: Running pass: CGProfilePass
 ; CHECK-O: Running pass: GlobalDCEPass
 ; CHECK-O: Running pass: ConstantMergePass


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