[InstCombine] Fold (add (add A, 1), (sext (icmp ne A, 0))) to call umax(A, 1)

Author: Ruhung

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -1775,6 +1775,15 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
     }
   }
 
+  // (add (add A, 1), (sext (icmp ne A, 0))) => call umax(A, 1)
+  if (match(LHS, m_OneUse(m_Add(m_Value(A), m_One()))) &&
+      match(RHS, m_OneUse(m_SExt(m_OneUse(m_SpecificICmp(
+                     ICmpInst::ICMP_NE, m_Specific(A), m_ZeroInt())))))) {
+    Value *OneConst = ConstantInt::get(A->getType(), 1);
+    Value *UMax = Builder.CreateBinaryIntrinsic(Intrinsic::umax, A, OneConst);
+    return replaceInstUsesWith(I, UMax);
+  }
+
   if (Instruction *Ashr = foldAddToAshr(I))
     return Ashr;
 

llvm/test/Transforms/InstCombine/add-sext-icmp.ll

@@ -9,10 +9,7 @@
 define i32 @add_sext_icmp(i32 %A) {
 ; CHECK-LABEL: define i32 @add_sext_icmp(
 ; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT:    [[ADD1:%.*]] = add i32 [[A]], 1
-; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i32 [[A]], 0
-; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[ICMP]] to i32
-; CHECK-NEXT:    [[ADD2:%.*]] = add i32 [[ADD1]], [[SEXT]]
+; CHECK-NEXT:    [[ADD2:%.*]] = call i32 @llvm.umax.i32(i32 [[A]], i32 1)
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;
   %add1 = add i32 %A, 1
@@ -25,10 +22,7 @@ define i32 @add_sext_icmp(i32 %A) {
 define i32 @add_sext_icmp_commutative(i32 %A) {
 ; CHECK-LABEL: define i32 @add_sext_icmp_commutative(
 ; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT:    [[ADD1:%.*]] = add i32 [[A]], 1
-; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i32 [[A]], 0
-; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[ICMP]] to i32
-; CHECK-NEXT:    [[ADD2:%.*]] = add i32 [[ADD1]], [[SEXT]]
+; CHECK-NEXT:    [[ADD2:%.*]] = call i32 @llvm.umax.i32(i32 [[A]], i32 1)
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;
   %add1 = add i32 %A, 1
@@ -77,10 +71,7 @@ define i32 @add_sext_icmp_negative_pred(i32 %A) {
 define i32 @add_sext_icmp_multi_use_add2(i32 %A) {
 ; CHECK-LABEL: define i32 @add_sext_icmp_multi_use_add2(
 ; CHECK-SAME: i32 [[A:%.*]]) {
-; CHECK-NEXT:    [[ADD1:%.*]] = add i32 [[A]], 1
-; CHECK-NEXT:    [[ICMP:%.*]] = icmp ne i32 [[A]], 0
-; CHECK-NEXT:    [[SEXT:%.*]] = sext i1 [[ICMP]] to i32
-; CHECK-NEXT:    [[ADD2:%.*]] = add i32 [[ADD1]], [[SEXT]]
+; CHECK-NEXT:    [[ADD2:%.*]] = call i32 @llvm.umax.i32(i32 [[A]], i32 1)
 ; CHECK-NEXT:    call void @use(i32 [[ADD2]])
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;