Index: llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -803,6 +803,32 @@
                                             const Value *FalseVal,
                                             InstCombiner::BuilderTy &Builder) {
   ICmpInst::Predicate Pred = ICI->getPredicate();
+  // (a == 0) : 0 : a - 1 -> usub.sat(a, 1)
+  if (Pred == ICmpInst::ICMP_EQ) {
+    Value *A = ICI->getOperand(0);
+    Value *B = ICI->getOperand(1);
+
+    if (!match(B, m_Zero()))
+      return nullptr;
+
+    if (match(FalseVal, m_Zero())) {
+      if (Pred == ICmpInst::ICMP_NE) {
+        Pred = ICmpInst::getSwappedPredicate(Pred);
+        std::swap(TrueVal, FalseVal);
+      }
+    }
+
+    if (!match(TrueVal, m_Zero()))
+      return nullptr;
+
+    Value *One = ConstantInt::get(A->getType(), 1);
+    APInt APOne = cast<ConstantInt>(One)->getValue();
+    if (match(FalseVal, m_Add(m_Specific(A), m_SpecificInt(-APOne)))) {
+      return Builder.CreateBinaryIntrinsic(Intrinsic::usub_sat, A, One);
+    }
+    return nullptr;
+  }
+
   if (!ICmpInst::isUnsigned(Pred))
     return nullptr;
 
Index: llvm/test/Transforms/InstCombine/saturating-add-sub.ll
===================================================================
--- llvm/test/Transforms/InstCombine/saturating-add-sub.ll
+++ llvm/test/Transforms/InstCombine/saturating-add-sub.ll
@@ -520,6 +520,91 @@
   ret i8 %x2
 }
 
+; Can simplify zero check followed by decrement
+define i8 @test_simplify_decrement(i8 %a) {
+; CHECK-LABEL: @test_simplify_decrement(
+; CHECK-NEXT:    [[I2:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[A:%.*]], i8 1)
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp eq i8 %a, 0
+  %i1 = sub i8 %a, 1
+  %i2 = select i1 %i, i8 0, i8 %i1
+  ret i8 %i2
+}
+
+define i8 @test_simplify_decrement_ne(i8 %a) {
+; CHECK-LABEL: @test_simplify_decrement_ne(
+; CHECK-NEXT:    [[I2:%.*]] = call i8 @llvm.usub.sat.i8(i8 [[A:%.*]], i8 1)
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp ne i8 %a, 0
+  %i1 = sub i8 %a, 1
+  %i2 = select i1 %i, i8 %i1, i8 0
+  ret i8 %i2
+}
+
+define i8 @test_simplify_decrement_invalid_ne(i8 %a) {
+; CHECK-LABEL: @test_simplify_decrement_invalid_ne(
+; CHECK-NEXT:    [[I_NOT:%.*]] = icmp eq i8 [[A:%.*]], 0
+; CHECK-NEXT:    [[I2:%.*]] = sext i1 [[I_NOT]] to i8
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp ne i8 %a, 0
+  %i1 = sub i8 %a, 1
+  %i2 = select i1 %i, i8 0, i8 %i1
+  ret i8 %i2
+}
+
+define i8 @test_invalid_simplify_sub2(i8 %a) {
+; CHECK-LABEL: @test_invalid_simplify_sub2(
+; CHECK-NEXT:    [[I:%.*]] = icmp eq i8 [[A:%.*]], 0
+; CHECK-NEXT:    [[I1:%.*]] = add i8 [[A]], -2
+; CHECK-NEXT:    [[I2:%.*]] = select i1 [[I]], i8 0, i8 [[I1]]
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp eq i8 %a, 0
+  %i1 = sub i8 %a, 2
+  %i2 = select i1 %i, i8 0, i8 %i1
+  ret i8 %i2
+}
+
+define i8 @test_invalid_simplify_eq1(i8 %a) {
+; CHECK-LABEL: @test_invalid_simplify_eq1(
+; CHECK-NEXT:    [[I1:%.*]] = add i8 [[A:%.*]], -1
+; CHECK-NEXT:    ret i8 [[I1]]
+;
+  %i = icmp eq i8 %a, 1
+  %i1 = sub i8 %a, 1
+  %i2 = select i1 %i, i8 0, i8 %i1
+  ret i8 %i2
+}
+
+define i8 @test_invalid_simplify_select_1(i8 %a) {
+; CHECK-LABEL: @test_invalid_simplify_select_1(
+; CHECK-NEXT:    [[I:%.*]] = icmp eq i8 [[A:%.*]], 0
+; CHECK-NEXT:    [[I1:%.*]] = add i8 [[A]], -1
+; CHECK-NEXT:    [[I2:%.*]] = select i1 [[I]], i8 1, i8 [[I1]]
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp eq i8 %a, 0
+  %i1 = sub i8 %a, 1
+  %i2 = select i1 %i, i8 1, i8 %i1
+  ret i8 %i2
+}
+
+define i8 @test_invalid_simplify_other(i8 %a, i8 %b) {
+; CHECK-LABEL: @test_invalid_simplify_other(
+; CHECK-NEXT:    [[I:%.*]] = icmp eq i8 [[A:%.*]], 1
+; CHECK-NEXT:    [[I1:%.*]] = add i8 [[B:%.*]], -1
+; CHECK-NEXT:    [[I2:%.*]] = select i1 [[I]], i8 0, i8 [[I1]]
+; CHECK-NEXT:    ret i8 [[I2]]
+;
+  %i = icmp eq i8 %a, 1
+  %i1 = sub i8 %b, 1
+  %i2 = select i1 %i, i8 0, i8 %i1
+  ret i8 %i2
+}
+
 define <2 x i8> @test_vector_usub_combine(<2 x i8> %a) {
 ; CHECK-LABEL: @test_vector_usub_combine(
 ; CHECK-NEXT:    [[TMP1:%.*]] = call <2 x i8> @llvm.usub.sat.v2i8(<2 x i8> [[A:%.*]], <2 x i8> <i8 30, i8 30>)