[llvm] LICM: use IRBuilder in hoist BO assoc (PR #106978)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon updated https://github.com/llvm/llvm-project/pull/106978

>From 225f0c1ea71eb416a3462528fa1d16f3895538ba Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Mon, 2 Sep 2024 12:50:21 +0100
Subject: [PATCH 1/2] LICM: use PatternMatch, IRBuilder in hoist BO assoc

Use PatternMatch when matching binary operators in hoistBOAssociation,
in order to make it easy to extend (this change is an NFC). Also use
IRBuilder when creating the new invariant instruction, so that the
constant-folder has an opportunity to constant-fold the new Instruction
that we desire to create (this change is not an NFC, and is a minor
improvement).
---
 llvm/lib/Transforms/Scalar/LICM.cpp        | 9 ++++++---
 llvm/test/Transforms/LICM/sink-foldable.ll | 3 +--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index 86c7dceffc5245..b1b0f01fa55b1c 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2841,15 +2841,18 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
   auto *Preheader = L.getLoopPreheader();
   assert(Preheader && "Loop is not in simplify form?");
 
-  auto *Inv = BinaryOperator::Create(Opcode, C1, C2, "invariant.op",
-                                     Preheader->getTerminator()->getIterator());
+  IRBuilder<> Builder(Preheader->getTerminator());
+  auto *Inv = Builder.CreateBinOp(Opcode, C1, C2, "invariant.op");
+
   auto *NewBO = BinaryOperator::Create(
       Opcode, LV, Inv, BO->getName() + ".reass", BO->getIterator());
 
   // Copy NUW for ADDs if both instructions have it.
   if (Opcode == Instruction::Add && BO->hasNoUnsignedWrap() &&
       BO0->hasNoUnsignedWrap()) {
-    Inv->setHasNoUnsignedWrap(true);
+    // If the constant-folder didn't kick in, and a new Instruction was created.
+    if (auto *I = dyn_cast<Instruction>(Inv))
+      I->setHasNoUnsignedWrap(true);
     NewBO->setHasNoUnsignedWrap(true);
   }
 
diff --git a/llvm/test/Transforms/LICM/sink-foldable.ll b/llvm/test/Transforms/LICM/sink-foldable.ll
index 36e2eab6313dcd..d1cf3de5301b29 100644
--- a/llvm/test/Transforms/LICM/sink-foldable.ll
+++ b/llvm/test/Transforms/LICM/sink-foldable.ll
@@ -77,7 +77,6 @@ return:
 define ptr @test2(i32 %j, ptr readonly %P, ptr readnone %Q) {
 ; CHECK-LABEL: @test2(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[INVARIANT_OP:%.*]] = add i32 1, 1
 ; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
 ; CHECK:       for.cond:
 ; CHECK-NEXT:    [[I_ADDR_0:%.*]] = phi i32 [ [[ADD_REASS:%.*]], [[IF_END:%.*]] ]
@@ -98,7 +97,7 @@ define ptr @test2(i32 %j, ptr readonly %P, ptr readnone %Q) {
 ; CHECK-NEXT:    [[ARRAYIDX2:%.*]] = getelementptr inbounds ptr, ptr [[ADD_PTR]], i64 [[IDX2_EXT]]
 ; CHECK-NEXT:    [[L1:%.*]] = load ptr, ptr [[ARRAYIDX2]], align 8
 ; CHECK-NEXT:    [[CMP2:%.*]] = icmp ugt ptr [[L1]], [[Q]]
-; CHECK-NEXT:    [[ADD_REASS]] = add i32 [[I_ADDR]], [[INVARIANT_OP]]
+; CHECK-NEXT:    [[ADD_REASS]] = add i32 [[I_ADDR]], 2
 ; CHECK-NEXT:    br i1 [[CMP2]], label [[LOOPEXIT2:%.*]], label [[FOR_COND]]
 ; CHECK:       loopexit0:
 ; CHECK-NEXT:    [[P0:%.*]] = phi ptr [ null, [[FOR_COND]] ]

>From 063ddb19283fdceea83a818964d8273094c81e33 Mon Sep 17 00:00:00 2001
From: Ramkumar Ramachandra <ramkumar.ramachandra at codasip.com>
Date: Tue, 3 Sep 2024 15:25:33 +0100
Subject: [PATCH 2/2] LICM: improve a comment

---
 llvm/lib/Transforms/Scalar/LICM.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Scalar/LICM.cpp b/llvm/lib/Transforms/Scalar/LICM.cpp
index b1b0f01fa55b1c..5e3701d3fb922e 100644
--- a/llvm/lib/Transforms/Scalar/LICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LICM.cpp
@@ -2850,7 +2850,7 @@ static bool hoistBOAssociation(Instruction &I, Loop &L,
   // Copy NUW for ADDs if both instructions have it.
   if (Opcode == Instruction::Add && BO->hasNoUnsignedWrap() &&
       BO0->hasNoUnsignedWrap()) {
-    // If the constant-folder didn't kick in, and a new Instruction was created.
+    // If `Inv` was not constant-folded, a new Instruction has been created.
     if (auto *I = dyn_cast<Instruction>(Inv))
       I->setHasNoUnsignedWrap(true);
     NewBO->setHasNoUnsignedWrap(true);