[PATCH] D147597: [InstCombine] Fold icmp(Positive1 * X * Y + Positive2) --> icmp(X * Y)

[Jun Zhang via Phabricator via llvm-commits]

junaire updated this revision to Diff 511046.
junaire added a comment.

Rework


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D147597/new/

https://reviews.llvm.org/D147597

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/icmp.ll


Index: llvm/test/Transforms/InstCombine/icmp.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp.ll
+++ llvm/test/Transforms/InstCombine/icmp.ll
@@ -4631,10 +4631,10 @@
 define i1 @mul_add_constant_sgt(i8 %a, i8 %b) {
 ; CHECK-LABEL: @mul_add_constant_sgt(
 ; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i8 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[ADD:%.*]] = or i8 [[MUL1]], 24
-; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[ADD]], 0
+; CHECK-NEXT:    [[CMP:%.*]] = icmp sgt i8 [[MUL1]], -1
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
+
   %mul1 = mul nsw i8 %a, %b
   %add = or i8 %mul1, 24
   %cmp = icmp sgt i8 %add, 0
@@ -4655,8 +4655,7 @@
 define i1 @mul_add_constant_sle(i8 %a, i8 %b) {
 ; CHECK-LABEL: @mul_add_constant_sle(
 ; CHECK-NEXT:    [[MUL1:%.*]] = mul nsw i8 [[A:%.*]], [[B:%.*]]
-; CHECK-NEXT:    [[ADD:%.*]] = or i8 [[MUL1]], 24
-; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 [[ADD]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i8 [[MUL1]], 0
 ; CHECK-NEXT:    ret i1 [[CMP]]
 ;
   %mul1 = mul nsw i8 %a, %b
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -1338,11 +1338,34 @@
     if (Instruction *Res = processUGT_ADDCST_ADD(Cmp, A, B, CI2, CI, *this))
       return Res;
 
-  // icmp(phi(C1, C2, ...), C) -> phi(icmp(C1, C), icmp(C2, C), ...).
   Constant *C = dyn_cast<Constant>(Op1);
   if (!C)
     return nullptr;
 
+  BinaryOperator *BO;
+  const APInt *LHS, *RHS;
+  if (match(Op0, m_c_Or(m_BinOp(BO), m_APInt(LHS))) &&
+      match(Op1, m_APInt(RHS))) {
+    if (LHS->isStrictlyPositive() && RHS->isNonNegative()) {
+      auto Relax = [&](ICmpInst::Predicate Pred, Value *X) {
+        Value *NewCmp = Builder.CreateICmp(
+            Pred, X, ConstantInt::getNullValue(X->getType()));
+        return replaceInstUsesWith(Cmp, NewCmp);
+      };
+      switch (Pred) {
+      case ICmpInst::ICMP_SLE:
+      case ICmpInst::ICMP_SLT:
+        return Relax(ICmpInst::ICMP_SLT, BO);
+      case ICmpInst::ICMP_SGE:
+      case ICmpInst::ICMP_SGT:
+        return Relax(ICmpInst::ICMP_SGE, BO);
+      default:
+        break;
+      }
+    }
+  }
+
+  // icmp(phi(C1, C2, ...), C) -> phi(icmp(C1, C), icmp(C2, C), ...).
   if (auto *Phi = dyn_cast<PHINode>(Op0))
     if (all_of(Phi->operands(), [](Value *V) { return isa<Constant>(V); })) {
       Type *Ty = Cmp.getType();


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