preserve nsw flag

Author: el-ev

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -1895,7 +1895,11 @@ Instruction *InstCombinerImpl::visitCallInst(CallInst &CI) {
     if (match(I0, m_OneUse(m_NUWShl(m_Value(Base), m_Value(Shamt1)))) &&
         match(I1, m_OneUse(m_NUWShl(m_Deferred(Base), m_Value(Shamt2))))) {
       Value *MaxMin = Builder.CreateBinaryIntrinsic(IID, Shamt1, Shamt2);
-      return BinaryOperator::CreateNUWShl(Base, MaxMin);
+      auto *NewShl = BinaryOperator::CreateNUWShl(Base, MaxMin);
+      if (cast<BinaryOperator>(I0)->hasNoSignedWrap() &&
+          cast<BinaryOperator>(I1)->hasNoSignedWrap())
+        NewShl->setHasNoSignedWrap();
+      return NewShl;
     }
 
     // If both operands of unsigned min/max are sign-extended, it is still ok

llvm/test/Transforms/InstCombine/shift-uminmax.ll

@@ -310,9 +310,8 @@ define i32 @test_umin_shl_no_nuw_flag(i32 %x, i32 %y) {
 define i32 @test_umax_shl_preserve_nsw(i32 %base, i32 %x, i32 %y) {
 ; CHECK-LABEL: define i32 @test_umax_shl_preserve_nsw(
 ; CHECK-SAME: i32 [[BASE:%.*]], i32 [[X:%.*]], i32 [[Y:%.*]]) {
-; CHECK-NEXT:    [[SHL_X:%.*]] = shl nuw nsw i32 [[BASE]], [[X]]
-; CHECK-NEXT:    [[SHL_Y:%.*]] = shl nuw nsw i32 [[BASE]], [[Y]]
-; CHECK-NEXT:    [[MAX:%.*]] = call i32 @llvm.umax.i32(i32 [[SHL_X]], i32 [[SHL_Y]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.umax.i32(i32 [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[MAX:%.*]] = shl nuw nsw i32 [[BASE]], [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[MAX]]
 ;
   %shl_x = shl nuw nsw i32 %base, %x
@@ -324,9 +323,8 @@ define i32 @test_umax_shl_preserve_nsw(i32 %base, i32 %x, i32 %y) {
 define i32 @test_umin_shl_preserve_nsw(i32 %base, i32 %x, i32 %y) {
 ; CHECK-LABEL: define i32 @test_umin_shl_preserve_nsw(
 ; CHECK-SAME: i32 [[BASE:%.*]], i32 [[X:%.*]], i32 [[Y:%.*]]) {
-; CHECK-NEXT:    [[SHL_X:%.*]] = shl nuw nsw i32 [[BASE]], [[X]]
-; CHECK-NEXT:    [[SHL_Y:%.*]] = shl nuw nsw i32 [[BASE]], [[Y]]
-; CHECK-NEXT:    [[MIN:%.*]] = call i32 @llvm.umin.i32(i32 [[SHL_X]], i32 [[SHL_Y]])
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @llvm.umin.i32(i32 [[X]], i32 [[Y]])
+; CHECK-NEXT:    [[MIN:%.*]] = shl nuw nsw i32 [[BASE]], [[TMP1]]
 ; CHECK-NEXT:    ret i32 [[MIN]]
 ;
   %shl_x = shl nuw nsw i32 %base, %x