Index: lib/Analysis/ValueTracking.cpp
===================================================================
--- lib/Analysis/ValueTracking.cpp
+++ lib/Analysis/ValueTracking.cpp
@@ -4299,6 +4299,20 @@
   return matchFastFloatClamp(Pred, CmpLHS, CmpRHS, TrueVal, FalseVal, LHS, RHS);
 }
 
+/// Helps to match a select pattern in case of a type mismatch.
+///
+/// The function processes the case when type of true and false values of a
+/// select instruction differs from type of the cmp instruction operands because
+/// of a cast instructon. The function checks if it is legal to move the cast
+/// operation after "select". If yes, it returns the new second value of
+/// "select" (with the assumption that cast is moved):
+/// 1. As operand of cast instruction when both values of "select" are same cast
+/// instructions.
+/// 2. As restored constant (by applying reverse cast operation) when the first
+/// value of the inital "select" is a cast operation and the second value is a
+/// constant.
+/// NOTE: We return only the new second value because the first value could be
+/// accessed as operand of cast instruction.
 static Value *lookThroughCast(CmpInst *CmpI, Value *V1, Value *V2,
                               Instruction::CastOps *CastOp) {
   auto *Cast1 = dyn_cast<CastInst>(V1);
@@ -4329,7 +4343,40 @@
       CastedTo = ConstantExpr::getTrunc(C, SrcTy, true);
     break;
   case Instruction::Trunc:
-    CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
+    const APInt *CmpConst, *SelectConst;
+    if (match(CmpI->getOperand(1), m_APInt(CmpConst)) &&
+        match(C, m_APInt(SelectConst))) {
+      // Here we have the following case:
+      //
+      //   %c = cmp iN %x, a
+      //   %t = trunc iN %y to iK
+      //   %sel = select i1 %c, iK %t, iK b
+      //
+      // where a and b are constants. We can always move trunc after select
+      // operation:
+      //
+      //   %c = cmp iN %x, a
+      //   %sel = select i1 %c, iN %y, iN B
+      //   %res = trunc iN %sel to iK
+      //
+      // Note that b could be extended in any way because we don't care about
+      // upper bits after truncation. It can't be abs pattern, because it would
+      // look like:
+      //
+      //   select i1 %c, x, -x.
+      //
+      // So only min/max pattern could be matched. Such match requires B == a.
+      // That is why copy upper bits from a.
+      auto SrcWidth = SrcTy->getScalarSizeInBits();
+      auto DstWidth = C->getType()->getScalarSizeInBits();
+      // Extend to source type with clear upper bits
+      APInt WidenedConst = SelectConst->zext(SrcWidth);
+      // Copy upper bits from constant in cmp instruction
+      WidenedConst |= CmpConst->getHiBits(SrcWidth - DstWidth).shl(DstWidth);
+      CastedTo = ConstantInt::getIntegerValue(SrcTy, WidenedConst);
+    } else {
+      CastedTo = ConstantExpr::getIntegerCast(C, SrcTy, CmpI->isSigned());
+    }
     break;
   case Instruction::FPTrunc:
     CastedTo = ConstantExpr::getFPExtend(C, SrcTy, true);
Index: test/Transforms/InstCombine/minmax-fold.ll
===================================================================
--- test/Transforms/InstCombine/minmax-fold.ll
+++ test/Transforms/InstCombine/minmax-fold.ll
@@ -688,3 +688,57 @@
   %sel = select <8 x i1> %cmp, <8 x float> %x, <8 x float> %y
   ret <8 x float> %sel
 }
+
+; Check that we look through cast and recognize min idiom.
+define zeroext i8 @look_through_cast1(i32 %x) {
+; CHECK-LABEL: @look_through_cast1(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 511
+; CHECK-NEXT:    [[RES1:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 511
+; CHECK-NEXT:    [[TMP2:%.*]] = trunc i32 [[RES1]] to i8
+; CHECK-NEXT:    ret i8 [[TMP2]]
+;
+  %cmp1 = icmp slt i32 %x, 511
+  %x_trunc = trunc i32 %x to i8
+  %res = select i1 %cmp1, i8 %x_trunc, i8 255
+  ret i8 %res
+}
+
+; Check that we look through cast but min is not recognized.
+define zeroext i8 @look_through_cast2(i32 %x) {
+; CHECK-LABEL: @look_through_cast2(
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp slt i32 [[X:%.*]], 510
+; CHECK-NEXT:    [[X_TRUNC:%.*]] = trunc i32 [[X]] to i8
+; CHECK-NEXT:    [[RES:%.*]] = select i1 [[CMP1]], i8 [[X_TRUNC]], i8 -1
+; CHECK-NEXT:    ret i8 [[RES]]
+;
+  %cmp1 = icmp slt i32 %x, 510
+  %x_trunc = trunc i32 %x to i8
+  %res = select i1 %cmp1, i8 %x_trunc, i8 255
+  ret i8 %res
+}
+
+define <2 x i8> @min_through_cast_vec1(<2 x i32> %x) {
+; CHECK-LABEL: @min_through_cast_vec1(
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt <2 x i32> [[X:%.*]], <i32 510, i32 511>
+; CHECK-NEXT:    [[X_TRUNC:%.*]] = trunc <2 x i32> [[X]] to <2 x i8>
+; CHECK-NEXT:    [[RES:%.*]] = select <2 x i1> [[CMP]], <2 x i8> [[X_TRUNC]], <2 x i8> <i8 -2, i8 -1>
+; CHECK-NEXT:    ret <2 x i8> [[RES]]
+;
+  %cmp = icmp slt <2 x i32> %x, <i32 510, i32 511>
+  %x_trunc = trunc <2 x i32> %x to <2 x i8>
+  %res = select <2 x i1> %cmp, <2 x i8> %x_trunc, <2 x i8> <i8 254, i8 255>
+  ret <2 x i8> %res
+}
+
+define <2 x i8> @min_through_cast_vec2(<2 x i32> %x) {
+; CHECK-LABEL: @min_through_cast_vec2(
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt <2 x i32> [[X:%.*]], <i32 511, i32 511>
+; CHECK-NEXT:    [[RES1:%.*]] = select <2 x i1> [[TMP1]], <2 x i32> [[X]], <2 x i32> <i32 511, i32 511>
+; CHECK-NEXT:    [[TMP2:%.*]] = trunc <2 x i32> [[RES1]] to <2 x i8>
+; CHECK-NEXT:    ret <2 x i8> [[TMP2]]
+;
+  %cmp = icmp slt <2 x i32> %x, <i32 511, i32 511>
+  %x_trunc = trunc <2 x i32> %x to <2 x i8>
+  %res = select <2 x i1> %cmp, <2 x i8> %x_trunc, <2 x i8> <i8 255, i8 255>
+  ret <2 x i8> %res
+}