[LoopInterchange] Enable it by default (WIP)

This is a work in progress patch to enable loop-interchange by default
and is a continuation of the RFC:

https://discourse.llvm.org/t/enabling-loop-interchange/82589

Basically, we promised to fix any compile-time and correctness issues in
the different components involved here (loop-interchange and dependence
analaysis.) before discussing enabling interchange by default. We think
are close to complete this; I would like to explain where we are and
wanted to check if there are any thoughts or concerns. A quick overview
of the correctness and compile-time improvements that we have made include:

Correctness:
- [LoopInterchange] Remove 'S' Scalar Dependencies (llvm#119345)
- [LoopInterchange] Fix overflow in cost calculation (llvm#111807)
- [LoopInterchange] Handle LE and GE correctly (PR llvm#124901) @kasuga-fj
- [DA] disambiguate evolution of base addresses (llvm#116628)

Compile-times:
- [LoopInterchange] Constrain number of load/stores in a loop (llvm#118973)
- [LoopInterchange] Bail out early if minimum loop nest is not met (llvm#115128)
- [LoopInterchange] Hoist isComputableLoopNest() in the control flow (llvm#124247)

And in terms of remaining work, we think we are very close to fixing
these depenence analysis issues:
- [DA] do not handle array accesses of different offsets (llvm#123436)
- [DA] Dependence analysis does not handle array accesses of different sizes (llvm#116630)
- [DA] use NSW arithmetic llvm#116632

The compile-time increase with a geomean increase of 0.19% looks good
(after committing llvm#124247), I think:

  stage1-O3:
  Benchmark
  kimwitu++        +0.10%
  sqlite3          +0.14%
  consumer-typeset +0.07%
  Bullet           +0.06%
  tramp3d-v4       +0.21%
  mafft            +0.39%
  ClamAVi          +0.06%
  lencod           +0.61%
  SPASS            +0.17%
  7zip             +0.08%
  geomean          +0.19%

See also:
http://llvm-compile-time-tracker.com/compare.php?from=19a7fe03b4f58c4f73ea91d5e63bc4c6e61f987b&to=b24f1367d68ee675ea93ecda4939208c6b68ae4b&stat=instructions%3Au

We might want to look into lencod to see if we can improve more, but not
sure it is strictly necessary.

Author: sjoerdmeijer

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -201,7 +201,7 @@ static cl::opt<bool> RunNewGVN("enable-newgvn", cl::init(false), cl::Hidden,
                                cl::desc("Run the NewGVN pass"));
 
 static cl::opt<bool> EnableLoopInterchange(
-    "enable-loopinterchange", cl::init(false), cl::Hidden,
+    "enable-loopinterchange", cl::init(true), cl::Hidden,
     cl::desc("Enable the experimental LoopInterchange Pass"));
 
 static cl::opt<bool> EnableUnrollAndJam("enable-unroll-and-jam",

llvm/test/Other/new-pm-defaults.ll

@@ -191,6 +191,7 @@
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-EP-LOOP-LATE-NEXT: Running pass: NoOpLoopPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchange
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-EP-LOOP-END-NEXT: Running pass: NoOpLoopPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo

llvm/test/Other/new-pm-thinlto-postlink-defaults.ll

@@ -122,6 +122,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass

llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll

@@ -108,6 +108,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass

llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll

@@ -117,6 +117,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass

llvm/test/Other/new-pm-thinlto-prelink-defaults.ll

@@ -154,6 +154,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass

llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll

@@ -157,6 +157,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: LoopFullUnrollPass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass

llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll

@@ -122,6 +122,7 @@
 ; CHECK-O-NEXT: Running pass: LoopIdiomRecognizePass
 ; CHECK-O-NEXT: Running pass: IndVarSimplifyPass
 ; CHECK-O-NEXT: Running pass: LoopDeletionPass
+; CHECK-O-NEXT: Running pass: LoopInterchangePass
 ; CHECK-O-NEXT: Running pass: SROAPass on foo
 ; CHECK-O23SZ-NEXT: Running pass: VectorCombinePass
 ; CHECK-O23SZ-NEXT: Running pass: MergedLoadStoreMotionPass