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[InstCombine] add tests for demanded/known bits of shifted constant; NFC

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These are variations of a missed analysis noted in:
https://llvm.org/PR48984
This commit is contained in:
Sanjay Patel 2021-02-03 12:07:06 -05:00
parent 93bf157993
commit b659297be9
1 changed files with 22 additions and 0 deletions
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22
test/Transforms/InstCombine/shift.ll
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@ -1795,3 +1795,25 @@ define void @ashr_out_of_range_1(i177* %A) {
store i177 %B28, i177* %G62, align 4
ret void
}
define i8 @lshr_mask_demand(i8 %x) {
; CHECK-LABEL: @lshr_mask_demand(
; CHECK-NEXT: [[S:%.*]] = lshr i8 63, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = and i8 [[S]], -32
; CHECK-NEXT: ret i8 [[R]]
;
%s = lshr i8 63, %x ; 0b00111111
%r = and i8 %s, 224 ; 0b11100000
ret i8 %r
}
define i8 @shl_mask_demand(i8 %x) {
; CHECK-LABEL: @shl_mask_demand(
; CHECK-NEXT: [[S:%.*]] = shl i8 12, [[X:%.*]]
; CHECK-NEXT: [[R:%.*]] = and i8 [[S]], 7
; CHECK-NEXT: ret i8 [[R]]
;
%s = shl i8 12, %x ; 0b00001100
%r = and i8 %s, 7 ; 0b00000111
ret i8 %r
}