Implement the fold and update tests

Author: Poseydon42

llvm/lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -1622,6 +1622,25 @@ Instruction *InstCombinerImpl::visitAdd(BinaryOperator &I) {
       A->getType()->isIntOrIntVectorTy(1))
     return replaceInstUsesWith(I, Constant::getNullValue(I.getType()));
 
+  // sext(A < B) + zext(A > B) => ucmp/scmp(A, B)
+  ICmpInst::Predicate LTPred, GTPred;
+  if (match(&I,
+            m_c_Add(m_SExt(m_c_ICmp(LTPred, m_Value(A), m_Value(B))),
+                    m_ZExt(m_c_ICmp(GTPred, m_Deferred(A), m_Deferred(B)))))) {
+    if (ICmpInst::isGT(LTPred)) {
+      std::swap(LTPred, GTPred);
+      std::swap(A, B);
+    }
+
+    if (ICmpInst::isLT(LTPred) && ICmpInst::isGT(GTPred) &&
+        ICmpInst::isSigned(LTPred) == ICmpInst::isSigned(GTPred))
+      return replaceInstUsesWith(
+          I, Builder.CreateIntrinsic(
+                 Ty,
+                 ICmpInst::isSigned(LTPred) ? Intrinsic::scmp : Intrinsic::ucmp,
+                 {A, B}));
+  }
+
   // A+B --> A|B iff A and B have no bits set in common.
   WithCache<const Value *> LHSCache(LHS), RHSCache(RHS);
   if (haveNoCommonBitsSet(LHSCache, RHSCache, SQ.getWithInstruction(&I)))

llvm/test/Transforms/InstCombine/add.ll

@@ -1277,8 +1277,8 @@ define <2 x i8> @ashr_add_commute(<2 x i1> %x, <2 x i1> %y) {
 
 define i32 @cmp_math(i32 %x, i32 %y) {
 ; CHECK-LABEL: @cmp_math(
-; CHECK-NEXT:    [[LT:%.*]] = icmp ult i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = zext i1 [[LT]] to i32
+; CHECK-NEXT:    [[S:%.*]] = call i32 @llvm.ucmp.i32.i32(i32 [[X:%.*]], i32 [[Y:%.*]])
+; CHECK-NEXT:    [[R:%.*]] = lshr i32 [[S]], 31
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %gt = icmp ugt i32 %x, %y

llvm/test/Transforms/InstCombine/sext-a-lt-b-plus-zext-a-gt-b-to-uscmp.ll

@@ -5,11 +5,7 @@
 define i8 @signed_add(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @signed_add(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp slt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[LT8:%.*]] = sext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp sgt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = zext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.scmp.i8.i32(i32 [[A]], i32 [[B]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp slt i32 %a, %b
@@ -24,11 +20,7 @@ define i8 @signed_add(i32 %a, i32 %b) {
 define i8 @unsigned_add(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @unsigned_add(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp ult i32 [[A]], [[B]]
-; CHECK-NEXT:    [[LT8:%.*]] = sext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp ugt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = zext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.ucmp.i8.i32(i32 [[A]], i32 [[B]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp ult i32 %a, %b
@@ -43,11 +35,7 @@ define i8 @unsigned_add(i32 %a, i32 %b) {
 define i8 @signed_add_commuted1(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @signed_add_commuted1(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp slt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[LT8:%.*]] = zext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp sgt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = sext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.scmp.i8.i32(i32 [[B]], i32 [[A]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp slt i32 %a, %b
@@ -61,11 +49,7 @@ define i8 @signed_add_commuted1(i32 %a, i32 %b) {
 define i8 @signed_add_commuted2(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @signed_add_commuted2(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp sgt i32 [[B]], [[A]]
-; CHECK-NEXT:    [[LT8:%.*]] = sext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp sgt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = zext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.scmp.i8.i32(i32 [[A]], i32 [[B]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp sgt i32 %b, %a
@@ -80,11 +64,7 @@ define i8 @signed_add_commuted2(i32 %a, i32 %b) {
 define i8 @signed_sub(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @signed_sub(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp slt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[LT8_NEG:%.*]] = sext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp sgt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = zext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8_NEG]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.scmp.i8.i32(i32 [[A]], i32 [[B]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp slt i32 %a, %b
@@ -99,11 +79,7 @@ define i8 @signed_sub(i32 %a, i32 %b) {
 define i8 @unsigned_sub(i32 %a, i32 %b) {
 ; CHECK-LABEL: define i8 @unsigned_sub(
 ; CHECK-SAME: i32 [[A:%.*]], i32 [[B:%.*]]) {
-; CHECK-NEXT:    [[LT:%.*]] = icmp ult i32 [[A]], [[B]]
-; CHECK-NEXT:    [[LT8_NEG:%.*]] = sext i1 [[LT]] to i8
-; CHECK-NEXT:    [[GT:%.*]] = icmp ugt i32 [[A]], [[B]]
-; CHECK-NEXT:    [[GT8:%.*]] = zext i1 [[GT]] to i8
-; CHECK-NEXT:    [[R:%.*]] = add nsw i8 [[LT8_NEG]], [[GT8]]
+; CHECK-NEXT:    [[R:%.*]] = call i8 @llvm.ucmp.i8.i32(i32 [[A]], i32 [[B]])
 ; CHECK-NEXT:    ret i8 [[R]]
 ;
   %lt = icmp ult i32 %a, %b