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[InstCombine] Add test cases to show missed opportunities to remove compare instructions after cttz/ctlz/ctpop where some bits of the input is known.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@304224 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Craig Topper 2017-05-30 17:47:59 +00:00
parent 79654737d7
commit 7aecbf8e99
2 changed files with 44 additions and 0 deletions
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16
test/Transforms/InstCombine/ctpop.ll
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@ -52,3 +52,19 @@ define i1 @test4(i8 %arg) {
%res = icmp eq i8 %cnt, 2
ret i1 %res
}
; Test when the number of possible known bits isn't one less than a power of 2
; and the compare value is greater but less than the next power of 2.
; TODO: The icmp is unnecessary given the known bits of the input.
define i1 @test5(i32 %arg) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[ARG:%.*]], 3
; CHECK-NEXT: [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[AND]])
; CHECK-NEXT: [[RES:%.*]] = icmp eq i32 [[CNT]], 3
; CHECK-NEXT: ret i1 [[RES]]
;
%and = and i32 %arg, 3
%cnt = call i32 @llvm.ctpop.i32(i32 %and)
%res = icmp eq i32 %cnt, 3
ret i1 %res
}

28
test/Transforms/InstCombine/intrinsics.ll
View File

@ -305,6 +305,20 @@ define i1 @cttz_knownbits2(i32 %arg) {
ret i1 %res
}
; TODO: The icmp is unnecessary given the known bits of the input.
define i1 @cttz_knownbits3(i32 %arg) {
; CHECK-LABEL: @cttz_knownbits3(
; CHECK-NEXT: [[OR:%.*]] = or i32 [[ARG:%.*]], 4
; CHECK-NEXT: [[CNT:%.*]] = call i32 @llvm.cttz.i32(i32 [[OR]], i1 true) #2
; CHECK-NEXT: [[RES:%.*]] = icmp eq i32 [[CNT]], 3
; CHECK-NEXT: ret i1 [[RES]]
;
%or = or i32 %arg, 4
%cnt = call i32 @llvm.cttz.i32(i32 %or, i1 true) nounwind readnone
%res = icmp eq i32 %cnt, 3
ret i1 %res
}
define i8 @ctlz(i8 %a) {
; CHECK-LABEL: @ctlz(
; CHECK-NEXT: ret i8 2
@ -338,6 +352,20 @@ define i1 @ctlz_knownbits2(i8 %arg) {
ret i1 %res
}
; TODO: The icmp is unnecessary given the known bits of the input.
define i1 @ctlz_knownbits3(i8 %arg) {
; CHECK-LABEL: @ctlz_knownbits3(
; CHECK-NEXT: [[OR:%.*]] = or i8 [[ARG:%.*]], 32
; CHECK-NEXT: [[CNT:%.*]] = call i8 @llvm.ctlz.i8(i8 [[OR]], i1 true) #2
; CHECK-NEXT: [[RES:%.*]] = icmp eq i8 [[CNT]], 3
; CHECK-NEXT: ret i1 [[RES]]
;
%or = or i8 %arg, 32
%cnt = call i8 @llvm.ctlz.i8(i8 %or, i1 true) nounwind readnone
%res = icmp eq i8 %cnt, 3
ret i1 %res
}
define void @cmp.simplify(i32 %a, i32 %b, i1* %c) {
%lz = tail call i32 @llvm.ctlz.i32(i32 %a, i1 false) nounwind readnone
%lz.cmp = icmp eq i32 %lz, 32