Index: llvm/lib/Transforms/Utils/SimplifyCFG.cpp
===================================================================
--- llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -6129,10 +6129,14 @@
     // truncating it to the width of the bitmask is safe.
     Value *ShiftAmt = Builder.CreateZExtOrTrunc(Index, MapTy, "switch.cast");
 
-    // Multiply the shift amount by the element width.
+    // Multiply the shift amount by the element width. NUW/NSW can always be
+    // set, because WouldFitInRegister guarantees Index * ShiftAmt is in
+    // BitMap's bit width.
     ShiftAmt = Builder.CreateMul(
         ShiftAmt, ConstantInt::get(MapTy, BitMapElementTy->getBitWidth()),
-        "switch.shiftamt");
+        "switch.shiftamt",
+        /*HasNUW =*/true,
+        /*HasNSW =*/true);
 
     // Shift down.
     Value *DownShifted =
Index: llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv32.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv32.ll
+++ llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv32.ll
@@ -112,7 +112,7 @@
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[X:%.*]], 4
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[SW_EPILOG:%.*]]
 ; CHECK:       switch.lookup:
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[X]], 8
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i32 [[X]], 8
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 89655594, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8
 ; CHECK-NEXT:    [[SWITCH_GEP:%.*]] = getelementptr inbounds [4 x float], ptr @switch.table.h, i32 0, i32 [[X]]
Index: llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv64.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv64.ll
+++ llvm/test/Transforms/SimplifyCFG/RISCV/switch_to_lookup_table-rv64.ll
@@ -112,7 +112,7 @@
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[X:%.*]], 4
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[SW_EPILOG:%.*]]
 ; CHECK:       switch.lookup:
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[X]], 8
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i32 [[X]], 8
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 89655594, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8
 ; CHECK-NEXT:    [[SWITCH_GEP:%.*]] = getelementptr inbounds [4 x float], ptr @switch.table.h, i32 0, i32 [[X]]
Index: llvm/test/Transforms/SimplifyCFG/X86/CoveredLookupTable.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/X86/CoveredLookupTable.ll
+++ llvm/test/Transforms/SimplifyCFG/X86/CoveredLookupTable.ll
@@ -11,7 +11,7 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[SWITCH_TABLEIDX:%.*]] = sub i3 [[INPUT:%.*]], -4
 ; CHECK-NEXT:    [[SWITCH_CAST:%.*]] = zext i3 [[SWITCH_TABLEIDX]] to i24
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i24 [[SWITCH_CAST]], 3
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i24 [[SWITCH_CAST]], 3
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i24 7507338, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i24 [[SWITCH_DOWNSHIFT]] to i3
 ; CHECK-NEXT:    ret i3 [[SWITCH_MASKED]]
Index: llvm/test/Transforms/SimplifyCFG/X86/switch-to-lookup-large-types.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/X86/switch-to-lookup-large-types.ll
+++ llvm/test/Transforms/SimplifyCFG/X86/switch-to-lookup-large-types.ll
@@ -25,7 +25,7 @@
 ; INLINE-NEXT:  start:
 ; INLINE-NEXT:    [[TMP0:%.*]] = icmp ult i64 [[X:%.*]], 3
 ; INLINE-NEXT:    [[SWITCH_CAST:%.*]] = trunc i64 [[X]] to i24
-; INLINE-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i24 [[SWITCH_CAST]], 8
+; INLINE-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i24 [[SWITCH_CAST]], 8
 ; INLINE-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i24 131331, [[SWITCH_SHIFTAMT]]
 ; INLINE-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i24 [[SWITCH_DOWNSHIFT]] to i8
 ; INLINE-NEXT:    [[COMMON_RET_OP:%.*]] = select i1 [[TMP0]], i8 [[SWITCH_MASKED]], i8 10
@@ -69,7 +69,7 @@
 ; INLINE-NEXT:  start:
 ; INLINE-NEXT:    [[TMP0:%.*]] = icmp ult i128 [[X:%.*]], 3
 ; INLINE-NEXT:    [[SWITCH_CAST:%.*]] = trunc i128 [[X]] to i24
-; INLINE-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i24 [[SWITCH_CAST]], 8
+; INLINE-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i24 [[SWITCH_CAST]], 8
 ; INLINE-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i24 131331, [[SWITCH_SHIFTAMT]]
 ; INLINE-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i24 [[SWITCH_DOWNSHIFT]] to i8
 ; INLINE-NEXT:    [[COMMON_RET_OP:%.*]] = select i1 [[TMP0]], i8 [[SWITCH_MASKED]], i8 10
Index: llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
+++ llvm/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
@@ -124,7 +124,7 @@
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[X:%.*]], 4
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[SW_EPILOG:%.*]]
 ; CHECK:       switch.lookup:
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[X]], 8
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i32 [[X]], 8
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 89655594, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8
 ; CHECK-NEXT:    [[SWITCH_GEP:%.*]] = getelementptr inbounds [4 x float], ptr @switch.table.h, i32 0, i32 [[X]]
@@ -257,7 +257,7 @@
 ; CHECK-NEXT:    br i1 [[TMP0]], label [[SWITCH_LOOKUP:%.*]], label [[LOR_END]]
 ; CHECK:       switch.lookup:
 ; CHECK-NEXT:    [[SWITCH_CAST:%.*]] = zext i8 [[SWITCH_TABLEIDX]] to i59
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i59 [[SWITCH_CAST]], 1
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i59 [[SWITCH_CAST]], 1
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i59 -288230375765830623, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i59 [[SWITCH_DOWNSHIFT]] to i1
 ; CHECK-NEXT:    br label [[LOR_END]]
@@ -351,7 +351,7 @@
 ; CHECK-NEXT:  bb:
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[TMP:%.*]], 9
 ; CHECK-NEXT:    [[SWITCH_CAST:%.*]] = trunc i32 [[TMP]] to i9
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i9 [[SWITCH_CAST]], 1
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i9 [[SWITCH_CAST]], 1
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i9 3, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i9 [[SWITCH_DOWNSHIFT]] to i1
 ; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP0]], i1 [[SWITCH_MASKED]], i1 undef
@@ -1667,7 +1667,7 @@
 ; CHECK-NEXT:  entry:
 ; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[X:%.*]], 9
 ; CHECK-NEXT:    [[SWITCH_CAST:%.*]] = trunc i32 [[X]] to i9
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i9 [[SWITCH_CAST]], 1
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i9 [[SWITCH_CAST]], 1
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i9 -234, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i9 [[SWITCH_DOWNSHIFT]] to i1
 ; CHECK-NEXT:    [[STOREMERGE:%.*]] = select i1 [[TMP0]], i1 [[SWITCH_MASKED]], i1 false
Index: llvm/test/Transforms/SimplifyCFG/rangereduce.ll
===================================================================
--- llvm/test/Transforms/SimplifyCFG/rangereduce.ll
+++ llvm/test/Transforms/SimplifyCFG/rangereduce.ll
@@ -223,7 +223,7 @@
 ; CHECK-NEXT:    [[TMP3:%.*]] = or i8 [[TMP1]], [[TMP2]]
 ; CHECK-NEXT:    [[TMP4:%.*]] = icmp ult i8 [[TMP3]], 4
 ; CHECK-NEXT:    [[SWITCH_CAST:%.*]] = zext i8 [[TMP3]] to i32
-; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[SWITCH_CAST]], 8
+; CHECK-NEXT:    [[SWITCH_SHIFTAMT:%.*]] = mul nuw nsw i32 [[SWITCH_CAST]], 8
 ; CHECK-NEXT:    [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 -943228976, [[SWITCH_SHIFTAMT]]
 ; CHECK-NEXT:    [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8
 ; CHECK-NEXT:    [[COMMON_RET_OP:%.*]] = select i1 [[TMP4]], i8 [[SWITCH_MASKED]], i8 -93