[llvm] 9e83d13 - [LICM] Support logical AND/OR when hoisting min/max

Max Kazantsev via llvm-commits llvm-commits at lists.llvm.org
Fri Mar 10 03:07:35 PST 2023 

Author: Max Kazantsev
Date: 2023-03-10T18:07:15+07:00
New Revision: 9e83d13c9f77e300ebb7b94a1400de3c2d47b3d5

URL: https://github.com/llvm/llvm-project/commit/9e83d13c9f77e300ebb7b94a1400de3c2d47b3d5
DIFF: https://github.com/llvm/llvm-project/commit/9e83d13c9f77e300ebb7b94a1400de3c2d47b3d5.diff

LOG: [LICM] Support logical AND/OR when hoisting min/max

We can handle logical AND/OR in the same way as arithmetic AND/OR, it only
takes us freezing `RHS2` for which we may introduce a new use which didn't
exist before dynamically.

Differential Revision: https://reviews.llvm.org/D145771
Reviewed By: nikic

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/LICM.cpp
    llvm/test/Transforms/LICM/min_max.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 78b05ba07081..a79e3955ce18 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2418,11 +2418,19 @@ static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
   auto *Preheader = L.getLoopPreheader();
   assert(Preheader && "Loop is not in simplify form?");
   bool Inverse = false;
+  bool IsLogical = false;
   using namespace PatternMatch;
   Value *Cond1, *Cond2;
   if (match(&I, m_Or(m_Value(Cond1), m_Value(Cond2))))
     Inverse = true;
-  else if (!match(&I, m_And(m_Value(Cond1), m_Value(Cond2))))
+  else if (match(&I, m_LogicalOr(m_Value(Cond1), m_Value(Cond2)))) {
+    Inverse = true;
+    IsLogical = true;
+  } else if (match(&I, m_And(m_Value(Cond1), m_Value(Cond2)))) {
+    // Do nothing
+  } else if (match(&I, m_LogicalAnd(m_Value(Cond1), m_Value(Cond2))))
+    IsLogical = true;
+  else
     return false;
 
   auto MatchICmpAgainstInvariant = [&](Value *C, ICmpInst::Predicate &P,
@@ -2458,6 +2466,12 @@ static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
                          ? (UseMin ? Intrinsic::smin : Intrinsic::smax)
                          : (UseMin ? Intrinsic::umin : Intrinsic::umax);
   IRBuilder<> Builder(Preheader->getTerminator());
+  // We are about to create a new guaranteed use for RHS2 which might not exist
+  // before (if it was a non-taken input of logical and/or instruction). If it
+  // was poison, we need to freeze it. Note that no new use for LHS and RHS1 are
+  // introduced, so they don't need this.
+  if (IsLogical)
+    RHS2 = Builder.CreateFreeze(RHS2, RHS2->getName() + ".fr");
   Value *NewRHS = Builder.CreateBinaryIntrinsic(
       id, RHS1, RHS2, nullptr, StringRef("invariant.") +
                                    (ICmpInst::isSigned(P1) ? "s" : "u") +

diff  --git a/llvm/test/Transforms/LICM/min_max.ll b/llvm/test/Transforms/LICM/min_max.ll
index d9710daa1645..f17929abb604 100644
--- a/llvm/test/Transforms/LICM/min_max.ll
+++ b/llvm/test/Transforms/LICM/min_max.ll
@@ -721,17 +721,17 @@ exit:
   ret i32 %iv
 }
 
-; TODO: inv_2 needs freeze because hoisted umax would create a new use that didn't exist before.
+; inv_2 needs freeze because hoisted umax would create a new use that didn't exist before.
 ; Counter-example: %cmp_1 = false, %inv_2 = poison.
 define i32 @test_logical_and_ult_needs_freeze(i32 %start, i32 %inv_1, i32 %inv_2) {
 ; CHECK-LABEL: @test_logical_and_ult_needs_freeze(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INV_2_FR:%.*]] = freeze i32 [[INV_2:%.*]]
+; CHECK-NEXT:    [[INVARIANT_UMIN:%.*]] = call i32 @llvm.umin.i32(i32 [[INV_1:%.*]], i32 [[INV_2_FR]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp ult i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp ult i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = select i1 [[CMP_1]], i1 [[CMP_2]], i1 false
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV]], [[INVARIANT_UMIN]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
 ; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
@@ -753,17 +753,17 @@ exit:
   ret i32 %iv
 }
 
-; TODO: turn to %iv <u umin(inv_1, inv_2) and hoist it out of loop.
+; turn to %iv <u umin(inv_1, inv_2) and hoist it out of loop.
 ; https://alive2.llvm.org/ce/z/mhKGtT
 define i32 @test_logical_and_ult_pos(i32 %start, i32 %inv_1, i32 noundef %inv_2) {
 ; CHECK-LABEL: @test_logical_and_ult_pos(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INV_2_FR:%.*]] = freeze i32 [[INV_2:%.*]]
+; CHECK-NEXT:    [[INVARIANT_UMIN:%.*]] = call i32 @llvm.umin.i32(i32 [[INV_1:%.*]], i32 [[INV_2_FR]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp ult i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp ult i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = select i1 [[CMP_1]], i1 [[CMP_2]], i1 false
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV]], [[INVARIANT_UMIN]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
 ; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
@@ -785,16 +785,16 @@ exit:
   ret i32 %iv
 }
 
-; TODO: inv_2 needs freeze because hoisted umax would create a new use that didn't exist before.
+; inv_2 needs freeze because hoisted umax would create a new use that didn't exist before.
 define i32 @test_logical_or_ult_inv_needs_freeze(i32 %start, i32 %inv_1, i32 %inv_2) {
 ; CHECK-LABEL: @test_logical_or_ult_inv_needs_freeze(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INV_2_FR:%.*]] = freeze i32 [[INV_2:%.*]]
+; CHECK-NEXT:    [[INVARIANT_UMAX:%.*]] = call i32 @llvm.umax.i32(i32 [[INV_1:%.*]], i32 [[INV_2_FR]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp ult i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp ult i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = select i1 [[CMP_1]], i1 true, i1 [[CMP_2]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV]], [[INVARIANT_UMAX]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
 ; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
@@ -816,17 +816,17 @@ exit:
   ret i32 %iv
 }
 
-; TODO: turn to %iv <u umax(inv_1, inv_2) and hoist it out of loop.
+; turn to %iv <u umax(inv_1, inv_2) and hoist it out of loop.
 ; https://alive2.llvm.org/ce/z/zgyG5N
 define i32 @test_logical_or_ult_inv_pos(i32 %start, i32 %inv_1, i32 noundef %inv_2) {
 ; CHECK-LABEL: @test_logical_or_ult_inv_pos(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INV_2_FR:%.*]] = freeze i32 [[INV_2:%.*]]
+; CHECK-NEXT:    [[INVARIANT_UMAX:%.*]] = call i32 @llvm.umax.i32(i32 [[INV_1:%.*]], i32 [[INV_2_FR]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp ult i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp ult i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = select i1 [[CMP_1]], i1 true, i1 [[CMP_2]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp ult i32 [[IV]], [[INVARIANT_UMAX]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
 ; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:

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