[LICM] Drop -licm-n2-threshold option

This was a diagnostic option used to demonstrate a weakness in
the AST-based LICM implementation. This problem does not exist
in the MSSA-based LICM implementation, which has been enabled
for a long time now. As such, this option is no longer relevant.

diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 5e48809..fa62703 100644 (file)
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -117,13 +117,6 @@ static cl::opt<uint32_t> MaxNumUsesTraversed(
     cl::desc("Max num uses visited for identifying load "
              "invariance in loop using invariant start (default = 8)"));
 
-// Default value of zero implies we use the regular alias set tracker mechanism
-// instead of the cross product using AA to identify aliasing of the memory
-// location we are interested in.
-static cl::opt<int>
-LICMN2Theshold("licm-n2-threshold", cl::Hidden, cl::init(0),
-               cl::desc("How many instruction to cross product using AA"));
-
 // Experimental option to allow imprecision in LICM in pathological cases, in
 // exchange for faster compile. This is to be removed if MemorySSA starts to
 // address the same issue. This flag applies only when LICM uses MemorySSA
@@ -2413,48 +2406,7 @@ LoopInvariantCodeMotion::collectAliasInfoForLoop(Loop *L, LoopInfo *LI,
 static bool pointerInvalidatedByLoop(MemoryLocation MemLoc,
                                      AliasSetTracker *CurAST, Loop *CurLoop,
                                      AAResults *AA) {
-  // First check to see if any of the basic blocks in CurLoop invalidate *V.
-  bool isInvalidatedAccordingToAST = CurAST->getAliasSetFor(MemLoc).isMod();
-
-  if (!isInvalidatedAccordingToAST || !LICMN2Theshold)
-    return isInvalidatedAccordingToAST;
-
-  // Check with a diagnostic analysis if we can refine the information above.
-  // This is to identify the limitations of using the AST.
-  // The alias set mechanism used by LICM has a major weakness in that it
-  // combines all things which may alias into a single set *before* asking
-  // modref questions. As a result, a single readonly call within a loop will
-  // collapse all loads and stores into a single alias set and report
-  // invalidation if the loop contains any store. For example, readonly calls
-  // with deopt states have this form and create a general alias set with all
-  // loads and stores.  In order to get any LICM in loops containing possible
-  // deopt states we need a more precise invalidation of checking the mod ref
-  // info of each instruction within the loop and LI. This has a complexity of
-  // O(N^2), so currently, it is used only as a diagnostic tool since the
-  // default value of LICMN2Threshold is zero.
-
-  // Don't look at nested loops.
-  if (CurLoop->begin() != CurLoop->end())
-    return true;
-
-  int N = 0;
-  for (BasicBlock *BB : CurLoop->getBlocks())
-    for (Instruction &I : *BB) {
-      if (N >= LICMN2Theshold) {
-        LLVM_DEBUG(dbgs() << "Alasing N2 threshold exhausted for "
-                          << *(MemLoc.Ptr) << "\n");
-        return true;
-      }
-      N++;
-      auto Res = AA->getModRefInfo(&I, MemLoc);
-      if (isModSet(Res)) {
-        LLVM_DEBUG(dbgs() << "Aliasing failed on " << I << " for "
-                          << *(MemLoc.Ptr) << "\n");
-        return true;
-      }
-    }
-  LLVM_DEBUG(dbgs() << "Aliasing okay for " << *(MemLoc.Ptr) << "\n");
-  return false;
+  return CurAST->getAliasSetFor(MemLoc).isMod();
 }
 
 bool pointerInvalidatedByLoopWithMSSA(MemorySSA *MSSA, MemoryUse *MU,

diff --git a/llvm/test/Transforms/LICM/argmemonly-call.ll b/llvm/test/Transforms/LICM/argmemonly-call.ll
index 882e9a8..b015f60 100644 (file)
--- a/llvm/test/Transforms/LICM/argmemonly-call.ll
+++ b/llvm/test/Transforms/LICM/argmemonly-call.ll
@@ -1,9 +1,5 @@
-; RUN: opt -S -basic-aa -licm -licm-n2-threshold=0 -verify-memoryssa %s -enable-new-pm=0 | FileCheck %s --check-prefix=ALIAS-N2
-; RUN: opt -licm -basic-aa -licm-n2-threshold=200 < %s -S -enable-new-pm=0 | FileCheck %s --check-prefix=ALIAS-N2
-
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=0 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=0 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop-mssa(licm)' < %s -S | FileCheck %s --check-prefix=ALIAS-N2
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=200 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s --check-prefix=ALIAS-N2
+; RUN: opt -S -basic-aa -licm -verify-memoryssa %s -enable-new-pm=0 | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop-mssa(licm)' < %s -S | FileCheck %s
 
 declare i32 @foo() readonly argmemonly nounwind
 declare i32 @foo2() readonly nounwind
@@ -13,9 +9,6 @@ define void @test(i32* %loc) {
 ; CHECK-LABEL: @test
 ; CHECK: @foo
 ; CHECK-LABEL: loop:
-; ALIAS-N2-LABEL: @test
-; ALIAS-N2: @foo
-; ALIAS-N2-LABEL: loop:
   br label %loop
 
 loop:
@@ -29,9 +22,6 @@ define void @test_neg(i32* %loc) {
 ; CHECK-LABEL: @test_neg
 ; CHECK-LABEL: loop:
 ; CHECK: @foo
-; ALIAS-N2-LABEL: @test_neg
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2: @foo
   br label %loop
 
 loop:
@@ -44,9 +34,6 @@ define void @test2(i32* noalias %loc, i32* noalias %loc2) {
 ; CHECK-LABEL: @test2
 ; CHECK: @bar
 ; CHECK-LABEL: loop:
-; ALIAS-N2-LABEL: @test2
-; ALIAS-N2: @bar
-; ALIAS-N2-LABEL: loop:
   br label %loop
 
 loop:
@@ -60,9 +47,6 @@ define void @test3(i32* %loc) {
 ; CHECK-LABEL: @test3
 ; CHECK-LABEL: loop:
 ; CHECK: @bar
-; ALIAS-N2-LABEL: @test3
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2: @bar
   br label %loop
 
 loop:
@@ -78,9 +62,6 @@ define void @test4(i32* %loc, i32* %loc2) {
 ; CHECK-LABEL: @test4
 ; CHECK-LABEL: loop:
 ; CHECK: @bar
-; ALIAS-N2-LABEL: @test4
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2: @bar
   br label %loop
 
 loop:
@@ -90,20 +71,11 @@ loop:
 }
 
 declare i32 @foo_new(i32*) readonly
-; With the default AST mechanism used by LICM for alias analysis,
-; we clump foo_new with bar.
-; With the N2 Alias analysis diagnostic tool, we are able to hoist the
-; argmemonly bar call out of the loop.
-; Using MemorySSA we can also hoist bar.
 
 define void @test5(i32* %loc2, i32* noalias %loc) {
-; ALIAS-N2-LABEL: @test5
-; ALIAS-N2: @bar
-; ALIAS-N2-LABEL: loop:
-
 ; CHECK-LABEL: @test5
+; CHECK: @bar
 ; CHECK-LABEL: loop:
-; CHECK:  @bar
   br label %loop
 
 loop:
@@ -121,10 +93,6 @@ define void @test6(i32* noalias %loc, i32* noalias %loc2) {
 ; CHECK: %val = load i32, i32* %loc2
 ; CHECK-LABEL: loop:
 ; CHECK: @llvm.memcpy
-; ALIAS-N2-LABEL: @test6
-; ALIAS-N2: %val = load i32, i32* %loc2
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2: @llvm.memcpy
   br label %loop
 
 loop:
@@ -141,10 +109,6 @@ define void @test7(i32* noalias %loc, i32* noalias %loc2) {
 ; CHECK: %val = load i32, i32* %loc2
 ; CHECK-LABEL: loop:
 ; CHECK: @custom_memcpy
-; ALIAS-N2-LABEL: @test7
-; ALIAS-N2: %val = load i32, i32* %loc2
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2: @custom_memcpy
   br label %loop
 
 loop:

diff --git a/llvm/test/Transforms/LICM/invariant.start.ll b/llvm/test/Transforms/LICM/invariant.start.ll
index 73e23f0..bf0d826 100644 (file)
--- a/llvm/test/Transforms/LICM/invariant.start.ll
+++ b/llvm/test/Transforms/LICM/invariant.start.ll
@@ -1,7 +1,5 @@
-; RUN: opt -licm -basic-aa -licm-n2-threshold=0 < %s -S | FileCheck %s
-; RUN: opt -licm -basic-aa -licm-n2-threshold=200 < %s -S | FileCheck %s --check-prefix=ALIAS-N2
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=0 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=200 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s --check-prefix=ALIAS-N2
+; RUN: opt -licm -basic-aa < %s -S | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop-mssa(licm)' < %s -S | FileCheck %s
 
 define void @test1(i1 %cond, i32* %ptr) {
 ; CHECK-LABEL: @test1(
@@ -10,12 +8,6 @@ define void @test1(i1 %cond, i32* %ptr) {
 ; CHECK: %val = load i32, i32* %ptr
 ; CHECK-LABEL: loop:
 
-; ALIAS-N2-LABEL: @test1(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
-; ALIAS-N2: %val = load i32, i32* %ptr
-; ALIAS-N2-LABEL: loop:
-
 entry:
   br label %loop
 
@@ -35,12 +27,6 @@ define void @test2(i1 %cond, i32* %ptr) {
 ; CHECK: %val = load i32, i32* %ptr
 ; CHECK-LABEL: loop:
 ; CHECK: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %piv)
-
-; ALIAS-N2-LABEL: @test2(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2:         %val = load i32, i32* %ptr
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2:         call {}* @llvm.invariant.start.p0i32(i64 4, i32* %piv)
 entry:
   br label %loop
 
@@ -59,12 +45,6 @@ define void @test3(i1 %cond, i32* %ptr) {
 ; CHECK: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
 ; CHECK: %val = load i32, i32* %ptr
 ; CHECK-LABEL: loop:
-
-; ALIAS-N2-LABEL: @test3(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
-; ALIAS-N2: %val = load i32, i32* %ptr
-; ALIAS-N2-LABEL: loop:
 entry:
   br label %loop
 
@@ -87,13 +67,6 @@ define void @test4(i1 %cond, i32* %ptr) {
 ; CHECK:   store i32 0, i32* %ptr
 ; CHECK: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
 ; CHECK: %val = load i32, i32* %ptr
-
-; ALIAS-N2-LABEL: @test4(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2:   store i32 0, i32* %ptr
-; ALIAS-N2: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
-; ALIAS-N2: %val = load i32, i32* %ptr
 entry:
   br label %loop
 
@@ -114,13 +87,6 @@ define void @test5(i1 %cond, i32* %ptr) {
 ; CHECK:   store i32 0, i32* %ptr
 ; CHECK: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
 ; CHECK: %val = load i32, i32* %ptr
-
-; ALIAS-N2-LABEL: @test5(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2:   store i32 0, i32* %ptr
-; ALIAS-N2: call {}* @llvm.invariant.start.p0i32(i64 4, i32* %ptr)
-; ALIAS-N2: %val = load i32, i32* %ptr
 entry:
   br label %loop
 

diff --git a/llvm/test/Transforms/LICM/read-only-calls.ll b/llvm/test/Transforms/LICM/read-only-calls.ll
index c92ff14..c280f53 100644 (file)
--- a/llvm/test/Transforms/LICM/read-only-calls.ll
+++ b/llvm/test/Transforms/LICM/read-only-calls.ll
@@ -1,9 +1,5 @@
-; RUN: opt -S -basic-aa -licm -licm-n2-threshold=0 %s -enable-new-pm=0 | FileCheck %s --check-prefix=ALIAS-N2
-; RUN: opt -licm -basic-aa -licm-n2-threshold=200 < %s -S -enable-new-pm=0 | FileCheck %s --check-prefix=ALIAS-N2
-
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=0 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=0 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop-mssa(licm)' < %s -S | FileCheck %s --check-prefix=ALIAS-N2
-; RUN: opt -aa-pipeline=basic-aa -licm-n2-threshold=200 -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s --check-prefix=ALIAS-N2
+; RUN: opt -S -basic-aa -licm %s -enable-new-pm=0 | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop-mssa(licm)' < %s -S | FileCheck %s
 
 ; We should be able to hoist loads in presence of read only calls and stores
 ; that do not alias.
@@ -22,13 +18,8 @@ declare void @foo(i64, i32*) readonly
 define void @test1(i32* %ptr) {
 ; CHECK-LABEL: @test1(
 ; CHECK-LABEL: entry:
+; CHECK:         %val = load i32, i32* %ptr
 ; CHECK-LABEL: loop:
-; CHECK: %val = load i32, i32* %ptr
-
-; ALIAS-N2-LABEL: @test1(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2:         %val = load i32, i32* %ptr
-; ALIAS-N2-LABEL: loop:
 entry:
   br label %loop
 
@@ -46,13 +37,8 @@ loop:
 define void @test2(i32* %ptr) {
 ; CHECK-LABEL: @test2(
 ; CHECK-LABEL: entry:
-; CHECK: %val = load i32, i32* %ptr
+; CHECK:         %val = load i32, i32* %ptr
 ; CHECK-LABEL: loop:
-
-; ALIAS-N2-LABEL: @test2(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2:         %val = load i32, i32* %ptr
-; ALIAS-N2-LABEL: loop:
 entry:
   br label %loop
 
@@ -69,12 +55,7 @@ define void @test3(i32* %ptr) {
 ; CHECK-LABEL: @test3(
 ; CHECK-LABEL: entry:
 ; CHECK-LABEL: loop:
-; CHECK: %val = load i32, i32* %ptr
-
-; ALIAS-N2-LABEL: @test3(
-; ALIAS-N2-LABEL: entry:
-; ALIAS-N2-LABEL: loop:
-; ALIAS-N2:         %val = load i32, i32* %ptr
+; CHECK:         %val = load i32, i32* %ptr
 entry:
   br label %loop