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[LoopIdiom] 'arithmetic right-shift until zero': don't turn potentially infinite loops into finite ones 

Nowadays LLVM does not assume that all loops are finite,
so if we want to produce a finite loop from a potentially-infinite one,
we must ensure that the original loop is known to be a finite one.

For this transform, it only matters for arithmetic right-shifts.
For them, either the function or the loop must be known to
be `mustprogress`, or the original value being shifted must be known
to be non-negative (because iff the sign bit was set,
it will never become zero, but will become `-1` in the "end").

It would be really good for alive2 to actually complain about this,
but it currently does not: https://github.com/AliveToolkit/alive2/issues/726
This commit is contained in:
Roman Lebedev 2021-05-25 20:47:53 +03:00
parent 8e30b55c82
commit 149e018d12
No known key found for this signature in database
GPG Key ID: 083C3EBB4A1689E0
2 changed files with 213 additions and 36 deletions
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13
llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
View File

@ -2528,6 +2528,19 @@ static bool detectShiftUntilZeroIdiom(Loop *CurLoop, ScalarEvolution *SE,
return false;
}
// The new, countable, loop will certainly only run a known number of
// iterations, It won't be infinite. But the old loop might be infinite
// under certain conditions. For logical shifts, the value will become zero
// after at most bitwidth(%Val) loop iterations. However, for arithmetic
// right-shift, iff the sign bit was set, the value will never become zero,
// and the loop may never finish.
if (ValShifted->getOpcode() == Instruction::AShr &&
!CurLoop->getHeader()->getParent()->mustProgress() &&
!hasMustProgress(CurLoop) && !SE->isKnownNonNegative(SE->getSCEV(Val))) {
LLVM_DEBUG(dbgs() << DEBUG_TYPE " Can not prove the loop is finite.\n");
return false;
}
// Okay, idiom checks out.
return true;
}

236
llvm/test/Transforms/LoopIdiom/X86/arithmetic-right-shift-until-zero.ll
View File

@ -8,7 +8,7 @@ declare i8 @gen.i8()
; Most basic pattern; Note that iff the shift amount is offset, said offsetting
; must not cause an overflow, but `add nsw` is fine.
define i8 @p0(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @p0(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @p0(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -65,7 +65,7 @@ end:
}
; `add nuw` is also fine.
define i8 @p1(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @p1(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @p1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -122,7 +122,7 @@ end:
}
; `sub nsw` is also fine.
define i8 @p2(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @p2(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @p2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -178,7 +178,7 @@ end:
}
; But `sub nuw` is not fine..
define i8 @n3(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n3(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n3(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -226,7 +226,7 @@ end:
}
; Likewise, plain `sub` is not fine.
define i8 @n4(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n4(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n4(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -274,7 +274,7 @@ end:
}
; Likewise, plain `add` is not fine.
define i8 @n5(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n5(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n5(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -322,7 +322,7 @@ end:
}
; Of course, we don't have to have an offset
define i8 @p6(i8 %val, i8 %start) {
define i8 @p6(i8 %val, i8 %start) mustprogress {
; CHECK-LABEL: @p6(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -377,7 +377,7 @@ declare void @escape_inner.i7(i7, i7, i7, i1, i7)
declare void @escape_outer.i7(i7, i7, i7, i1, i7)
; Other bitwidths are fine also
define i7 @p7(i7 %val, i7 %start, i7 %extraoffset) {
define i7 @p7(i7 %val, i7 %start, i7 %extraoffset) mustprogress {
; CHECK-LABEL: @p7(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i7 @llvm.ctlz.i7(i7 [[VAL:%.*]], i1 false)
@ -434,7 +434,7 @@ end:
}
; Step must be 1
define i8 @n8(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n8(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n8(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -482,7 +482,7 @@ end:
}
; Cmp-br are commutable
define i8 @t9(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @t9(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @t9(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -540,7 +540,7 @@ end:
}
; We want to exit once it becomes zero
define i8 @n10(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n10(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n10(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -588,7 +588,7 @@ end:
}
; Once it compares zero, we want to exit, not exit when it compares non-zero
define i8 @n11(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n11(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n11(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -636,7 +636,7 @@ end:
}
; We must be comparing with 0
define i8 @n12(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n12(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n12(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -684,7 +684,7 @@ end:
}
; Loop must have a single block.
define i8 @n13(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n13(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n13(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -737,7 +737,7 @@ end:
}
; The comparison must have an equality predicate
define i8 @n14(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n14(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n14(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -785,7 +785,7 @@ end:
}
; offset computation can be commuted
define i8 @t15(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @t15(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @t15(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -842,7 +842,7 @@ end:
}
; But for `sub nsw`, it is not commutable.
define i8 @n16(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n16(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n16(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -890,7 +890,7 @@ end:
}
; The offset must be loop-invariant
define i8 @n17(i8 %val, i8 %start) {
define i8 @n17(i8 %val, i8 %start) mustprogress {
; CHECK-LABEL: @n17(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -940,7 +940,7 @@ end:
}
; Likewise for `sub nsw`.
define i8 @n18(i8 %val, i8 %start) {
define i8 @n18(i8 %val, i8 %start) mustprogress {
; CHECK-LABEL: @n18(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -990,7 +990,7 @@ end:
}
; The "induction variable" must be in the loop header.
define i8 @n19(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n19(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n19(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP_PREHEADER:%.*]]
@ -1045,7 +1045,7 @@ end:
}
; IV must really be a PHI
define i8 @n20(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n20(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n20(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -1093,7 +1093,7 @@ end:
}
; The induction should be actually increasing IV
define i8 @n21(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n21(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n21(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -1141,7 +1141,7 @@ end:
}
; We should not just blindly look for add, we should look what IV actually uses.
define i8 @n22(i8 %val, i8 %start, i8 %extraoffset) {
define i8 @n22(i8 %val, i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n22(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
@ -1201,7 +1201,7 @@ end:
ret i8 %iv.res
}
define i8 @n23(i8 %start, i8 %extraoffset) {
define i8 @n23(i8 %start, i8 %extraoffset) mustprogress {
; CHECK-LABEL: @n23(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
@ -1258,7 +1258,7 @@ declare void @escape_outer.i2(i2, i2, i2, i1, i2)
declare void @escape_inner.i3(i3, i3, i3, i1, i3)
declare void @escape_outer.i3(i3, i3, i3, i1, i3)
define i1 @t24_nooffset_i1(i1 %val, i1 %start) {
define i1 @t24_nooffset_i1(i1 %val, i1 %start) mustprogress {
; CHECK-LABEL: @t24_nooffset_i1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i1 @llvm.ctlz.i1(i1 [[VAL:%.*]], i1 false)
@ -1308,7 +1308,7 @@ end:
ret i1 %iv.res
}
define i2 @t25_nooffset_i2(i2 %val, i2 %start) {
define i2 @t25_nooffset_i2(i2 %val, i2 %start) mustprogress {
; CHECK-LABEL: @t25_nooffset_i2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i2 @llvm.ctlz.i2(i2 [[VAL:%.*]], i1 false)
@ -1358,7 +1358,7 @@ end:
ret i2 %iv.res
}
define i3 @t26_nooffset_i3(i3 %val, i3 %start) {
define i3 @t26_nooffset_i3(i3 %val, i3 %start) mustprogress {
; CHECK-LABEL: @t26_nooffset_i3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i3 @llvm.ctlz.i3(i3 [[VAL:%.*]], i1 false)
@ -1409,7 +1409,7 @@ end:
ret i3 %iv.res
}
define i1 @t27_addnsw_i1(i1 %val, i1 %start, i1 %extraoffset) {
define i1 @t27_addnsw_i1(i1 %val, i1 %start, i1 %extraoffset) mustprogress {
; CHECK-LABEL: @t27_addnsw_i1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i1 @llvm.ctlz.i1(i1 [[VAL:%.*]], i1 false)
@ -1463,7 +1463,7 @@ end:
ret i1 %iv.res
}
define i2 @t28_addnsw_i2(i2 %val, i2 %start, i2 %extraoffset) {
define i2 @t28_addnsw_i2(i2 %val, i2 %start, i2 %extraoffset) mustprogress {
; CHECK-LABEL: @t28_addnsw_i2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i2 @llvm.ctlz.i2(i2 [[VAL:%.*]], i1 false)
@ -1518,7 +1518,7 @@ end:
ret i2 %iv.res
}
define i3 @t29_addnsw_i3(i3 %val, i3 %start, i3 %extraoffset) {
define i3 @t29_addnsw_i3(i3 %val, i3 %start, i3 %extraoffset) mustprogress {
; CHECK-LABEL: @t29_addnsw_i3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i3 @llvm.ctlz.i3(i3 [[VAL:%.*]], i1 false)
@ -1574,7 +1574,7 @@ end:
ret i3 %iv.res
}
define i1 @t30_addnuw_i1(i1 %val, i1 %start, i1 %extraoffset) {
define i1 @t30_addnuw_i1(i1 %val, i1 %start, i1 %extraoffset) mustprogress {
; CHECK-LABEL: @t30_addnuw_i1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i1 @llvm.ctlz.i1(i1 [[VAL:%.*]], i1 false)
@ -1628,7 +1628,7 @@ end:
ret i1 %iv.res
}
define i2 @t31_addnuw_i2(i2 %val, i2 %start, i2 %extraoffset) {
define i2 @t31_addnuw_i2(i2 %val, i2 %start, i2 %extraoffset) mustprogress {
; CHECK-LABEL: @t31_addnuw_i2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i2 @llvm.ctlz.i2(i2 [[VAL:%.*]], i1 false)
@ -1683,7 +1683,7 @@ end:
ret i2 %iv.res
}
define i3 @t32_addnuw_i3(i3 %val, i3 %start, i3 %extraoffset) {
define i3 @t32_addnuw_i3(i3 %val, i3 %start, i3 %extraoffset) mustprogress {
; CHECK-LABEL: @t32_addnuw_i3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i3 @llvm.ctlz.i3(i3 [[VAL:%.*]], i1 false)
@ -1740,7 +1740,7 @@ end:
}
define i1 @t33_subnsw_i1(i1 %val, i1 %start, i1 %extraoffset) {
define i1 @t33_subnsw_i1(i1 %val, i1 %start, i1 %extraoffset) mustprogress {
; CHECK-LABEL: @t33_subnsw_i1(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i1 @llvm.ctlz.i1(i1 [[VAL:%.*]], i1 false)
@ -1794,7 +1794,7 @@ end:
ret i1 %iv.res
}
define i2 @t34_addnuw_i2(i2 %val, i2 %start, i2 %extraoffset) {
define i2 @t34_addnuw_i2(i2 %val, i2 %start, i2 %extraoffset) mustprogress {
; CHECK-LABEL: @t34_addnuw_i2(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i2 @llvm.ctlz.i2(i2 [[VAL:%.*]], i1 false)
@ -1848,7 +1848,7 @@ end:
ret i2 %iv.res
}
define i3 @t35_addnuw_i3(i3 %val, i3 %start, i3 %extraoffset) {
define i3 @t35_addnuw_i3(i3 %val, i3 %start, i3 %extraoffset) mustprogress {
; CHECK-LABEL: @t35_addnuw_i3(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i3 @llvm.ctlz.i3(i3 [[VAL:%.*]], i1 false)
@ -1902,3 +1902,167 @@ end:
ret i3 %iv.res
}
; For ashr, we must have knowledge that the original loop is finite.
define i8 @n36(i8 %val, i8 %start, i8 %extraoffset) {
; CHECK-LABEL: @n36(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i8 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[NBITS:%.*]] = add nsw i8 [[IV]], [[EXTRAOFFSET:%.*]]
; CHECK-NEXT: [[VAL_SHIFTED:%.*]] = ashr i8 [[VAL:%.*]], [[NBITS]]
; CHECK-NEXT: [[VAL_SHIFTED_ISZERO:%.*]] = icmp eq i8 [[VAL_SHIFTED]], 0
; CHECK-NEXT: [[IV_NEXT]] = add i8 [[IV]], 1
; CHECK-NEXT: call void @escape_inner(i8 [[IV]], i8 [[NBITS]], i8 [[VAL_SHIFTED]], i1 [[VAL_SHIFTED_ISZERO]], i8 [[IV_NEXT]])
; CHECK-NEXT: br i1 [[VAL_SHIFTED_ISZERO]], label [[END:%.*]], label [[LOOP]]
; CHECK: end:
; CHECK-NEXT: [[IV_RES:%.*]] = phi i8 [ [[IV]], [[LOOP]] ]
; CHECK-NEXT: [[NBITS_RES:%.*]] = phi i8 [ [[NBITS]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_RES:%.*]] = phi i8 [ [[VAL_SHIFTED]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_ISZERO_RES:%.*]] = phi i1 [ [[VAL_SHIFTED_ISZERO]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT_RES:%.*]] = phi i8 [ [[IV_NEXT]], [[LOOP]] ]
; CHECK-NEXT: call void @escape_outer(i8 [[IV_RES]], i8 [[NBITS_RES]], i8 [[VAL_SHIFTED_RES]], i1 [[VAL_SHIFTED_ISZERO_RES]], i8 [[IV_NEXT_RES]])
; CHECK-NEXT: ret i8 [[IV_RES]]
;
entry:
br label %loop
loop:
%iv = phi i8 [ %start, %entry ], [ %iv.next, %loop ]
%nbits = add nsw i8 %iv, %extraoffset
%val.shifted = ashr i8 %val, %nbits
%val.shifted.iszero = icmp eq i8 %val.shifted, 0
%iv.next = add i8 %iv, 1
call void @escape_inner(i8 %iv, i8 %nbits, i8 %val.shifted, i1 %val.shifted.iszero, i8 %iv.next)
br i1 %val.shifted.iszero, label %end, label %loop
end:
%iv.res = phi i8 [ %iv, %loop ]
%nbits.res = phi i8 [ %nbits, %loop ]
%val.shifted.res = phi i8 [ %val.shifted, %loop ]
%val.shifted.iszero.res = phi i1 [ %val.shifted.iszero, %loop ]
%iv.next.res = phi i8 [ %iv.next, %loop ]
call void @escape_outer(i8 %iv.res, i8 %nbits.res, i8 %val.shifted.res, i1 %val.shifted.iszero.res, i8 %iv.next.res)
ret i8 %iv.res
}
define i8 @p37(i8 %val, i8 %start, i8 %extraoffset) {
; CHECK-LABEL: @p37(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL:%.*]], i1 false)
; CHECK-NEXT: [[VAL_NUMACTIVEBITS:%.*]] = sub nuw nsw i8 8, [[VAL_NUMLEADINGZEROS]]
; CHECK-NEXT: [[TMP0:%.*]] = sub i8 0, [[EXTRAOFFSET:%.*]]
; CHECK-NEXT: [[VAL_NUMACTIVEBITS_OFFSET:%.*]] = add nsw i8 [[VAL_NUMACTIVEBITS]], [[TMP0]]
; CHECK-NEXT: [[IV_FINAL:%.*]] = call i8 @llvm.smax.i8(i8 [[VAL_NUMACTIVEBITS_OFFSET]], i8 [[START:%.*]])
; CHECK-NEXT: [[LOOP_BACKEDGETAKENCOUNT:%.*]] = sub nsw i8 [[IV_FINAL]], [[START]]
; CHECK-NEXT: [[LOOP_TRIPCOUNT:%.*]] = add nuw nsw i8 [[LOOP_BACKEDGETAKENCOUNT]], 1
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[LOOP_IV:%.*]] = phi i8 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[LOOP_IV_NEXT]] = add nuw nsw i8 [[LOOP_IV]], 1
; CHECK-NEXT: [[LOOP_IVCHECK:%.*]] = icmp eq i8 [[LOOP_IV_NEXT]], [[LOOP_TRIPCOUNT]]
; CHECK-NEXT: [[IV:%.*]] = add nsw i8 [[LOOP_IV]], [[START]]
; CHECK-NEXT: [[NBITS:%.*]] = add nsw i8 [[IV]], [[EXTRAOFFSET]]
; CHECK-NEXT: [[VAL_SHIFTED:%.*]] = ashr i8 [[VAL]], [[NBITS]]
; CHECK-NEXT: [[IV_NEXT:%.*]] = add i8 [[IV]], 1
; CHECK-NEXT: call void @escape_inner(i8 [[IV]], i8 [[NBITS]], i8 [[VAL_SHIFTED]], i1 [[LOOP_IVCHECK]], i8 [[IV_NEXT]])
; CHECK-NEXT: br i1 [[LOOP_IVCHECK]], label [[END:%.*]], label [[LOOP]]
; CHECK: end:
; CHECK-NEXT: [[IV_RES:%.*]] = phi i8 [ [[IV_FINAL]], [[LOOP]] ]
; CHECK-NEXT: [[NBITS_RES:%.*]] = phi i8 [ [[NBITS]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_RES:%.*]] = phi i8 [ [[VAL_SHIFTED]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_ISZERO_RES:%.*]] = phi i1 [ [[LOOP_IVCHECK]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT_RES:%.*]] = phi i8 [ [[IV_NEXT]], [[LOOP]] ]
; CHECK-NEXT: call void @escape_outer(i8 [[IV_RES]], i8 [[NBITS_RES]], i8 [[VAL_SHIFTED_RES]], i1 [[VAL_SHIFTED_ISZERO_RES]], i8 [[IV_NEXT_RES]])
; CHECK-NEXT: ret i8 [[IV_RES]]
;
entry:
br label %loop
loop:
%iv = phi i8 [ %start, %entry ], [ %iv.next, %loop ]
%nbits = add nsw i8 %iv, %extraoffset
%val.shifted = ashr i8 %val, %nbits
%val.shifted.iszero = icmp eq i8 %val.shifted, 0
%iv.next = add i8 %iv, 1
call void @escape_inner(i8 %iv, i8 %nbits, i8 %val.shifted, i1 %val.shifted.iszero, i8 %iv.next)
br i1 %val.shifted.iszero, label %end, label %loop, !llvm.loop !0
end:
%iv.res = phi i8 [ %iv, %loop ]
%nbits.res = phi i8 [ %nbits, %loop ]
%val.shifted.res = phi i8 [ %val.shifted, %loop ]
%val.shifted.iszero.res = phi i1 [ %val.shifted.iszero, %loop ]
%iv.next.res = phi i8 [ %iv.next, %loop ]
call void @escape_outer(i8 %iv.res, i8 %nbits.res, i8 %val.shifted.res, i1 %val.shifted.iszero.res, i8 %iv.next.res)
ret i8 %iv.res
}
!0 = distinct !{!0, !1}
!1 = !{!"llvm.loop.mustprogress"}
define i8 @p38(i8 %val.crude, i8 %start, i8 %extraoffset) {
; CHECK-LABEL: @p38(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[VAL:%.*]] = and i8 [[VAL_CRUDE:%.*]], 127
; CHECK-NEXT: [[VAL_NUMLEADINGZEROS:%.*]] = call i8 @llvm.ctlz.i8(i8 [[VAL]], i1 false)
; CHECK-NEXT: [[VAL_NUMACTIVEBITS:%.*]] = sub nuw nsw i8 8, [[VAL_NUMLEADINGZEROS]]
; CHECK-NEXT: [[TMP0:%.*]] = sub i8 0, [[EXTRAOFFSET:%.*]]
; CHECK-NEXT: [[VAL_NUMACTIVEBITS_OFFSET:%.*]] = add nsw i8 [[VAL_NUMACTIVEBITS]], [[TMP0]]
; CHECK-NEXT: [[IV_FINAL:%.*]] = call i8 @llvm.smax.i8(i8 [[VAL_NUMACTIVEBITS_OFFSET]], i8 [[START:%.*]])
; CHECK-NEXT: [[LOOP_BACKEDGETAKENCOUNT:%.*]] = sub nsw i8 [[IV_FINAL]], [[START]]
; CHECK-NEXT: [[LOOP_TRIPCOUNT:%.*]] = add nuw nsw i8 [[LOOP_BACKEDGETAKENCOUNT]], 1
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[LOOP_IV:%.*]] = phi i8 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: [[LOOP_IV_NEXT]] = add nuw nsw i8 [[LOOP_IV]], 1
; CHECK-NEXT: [[LOOP_IVCHECK:%.*]] = icmp eq i8 [[LOOP_IV_NEXT]], [[LOOP_TRIPCOUNT]]
; CHECK-NEXT: [[IV:%.*]] = add nsw i8 [[LOOP_IV]], [[START]]
; CHECK-NEXT: [[NBITS:%.*]] = add nsw i8 [[IV]], [[EXTRAOFFSET]]
; CHECK-NEXT: [[VAL_SHIFTED:%.*]] = ashr i8 [[VAL]], [[NBITS]]
; CHECK-NEXT: [[IV_NEXT:%.*]] = add i8 [[IV]], 1
; CHECK-NEXT: call void @escape_inner(i8 [[IV]], i8 [[NBITS]], i8 [[VAL_SHIFTED]], i1 [[LOOP_IVCHECK]], i8 [[IV_NEXT]])
; CHECK-NEXT: br i1 [[LOOP_IVCHECK]], label [[END:%.*]], label [[LOOP]]
; CHECK: end:
; CHECK-NEXT: [[IV_RES:%.*]] = phi i8 [ [[IV_FINAL]], [[LOOP]] ]
; CHECK-NEXT: [[NBITS_RES:%.*]] = phi i8 [ [[NBITS]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_RES:%.*]] = phi i8 [ [[VAL_SHIFTED]], [[LOOP]] ]
; CHECK-NEXT: [[VAL_SHIFTED_ISZERO_RES:%.*]] = phi i1 [ [[LOOP_IVCHECK]], [[LOOP]] ]
; CHECK-NEXT: [[IV_NEXT_RES:%.*]] = phi i8 [ [[IV_NEXT]], [[LOOP]] ]
; CHECK-NEXT: call void @escape_outer(i8 [[IV_RES]], i8 [[NBITS_RES]], i8 [[VAL_SHIFTED_RES]], i1 [[VAL_SHIFTED_ISZERO_RES]], i8 [[IV_NEXT_RES]])
; CHECK-NEXT: ret i8 [[IV_RES]]
;
entry:
%val = and i8 %val.crude, 127
br label %loop
loop:
%iv = phi i8 [ %start, %entry ], [ %iv.next, %loop ]
%nbits = add nsw i8 %iv, %extraoffset
%val.shifted = ashr i8 %val, %nbits
%val.shifted.iszero = icmp eq i8 %val.shifted, 0
%iv.next = add i8 %iv, 1
call void @escape_inner(i8 %iv, i8 %nbits, i8 %val.shifted, i1 %val.shifted.iszero, i8 %iv.next)
br i1 %val.shifted.iszero, label %end, label %loop
end:
%iv.res = phi i8 [ %iv, %loop ]
%nbits.res = phi i8 [ %nbits, %loop ]
%val.shifted.res = phi i8 [ %val.shifted, %loop ]
%val.shifted.iszero.res = phi i1 [ %val.shifted.iszero, %loop ]
%iv.next.res = phi i8 [ %iv.next, %loop ]
call void @escape_outer(i8 %iv.res, i8 %nbits.res, i8 %val.shifted.res, i1 %val.shifted.iszero.res, i8 %iv.next.res)
ret i8 %iv.res
}