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[GISel] Fold bitreverse(shl/srl(bitreverse(x),y)) -> srl/shl(x,y) (ll…
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…vm#91355)

Sibling patch to llvm#89897
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@RKSimon
RKSimon authored May 8, 2024
1 parent cec6665 commit 965f3ca
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26 changes: 25 additions & 1 deletion llvm/include/llvm/Target/GlobalISel/Combine.td
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Original file line number Diff line number Diff line change
Expand Up @@ -325,6 +325,28 @@ def reduce_shl_of_extend : GICombineRule<
[{ return Helper.matchCombineShlOfExtend(*${mi}, ${matchinfo}); }]),
(apply [{ Helper.applyCombineShlOfExtend(*${mi}, ${matchinfo}); }])>;

// Combine bitreverse(shl (bitreverse x), y)) -> (lshr x, y)
def bitreverse_shl : GICombineRule<
(defs root:$d),
(match (G_BITREVERSE $rev, $val),
(G_SHL $src, $rev, $amt):$mi,
(G_BITREVERSE $d, $src),
[{ return Helper.isLegalOrBeforeLegalizer({TargetOpcode::G_LSHR,
{MRI.getType(${val}.getReg()),
MRI.getType(${amt}.getReg())}}); }]),
(apply (G_LSHR $d, $val, $amt))>;

// Combine bitreverse(lshr (bitreverse x), y)) -> (shl x, y)
def bitreverse_lshr : GICombineRule<
(defs root:$d, build_fn_matchinfo:$matchinfo),
(match (G_BITREVERSE $rev, $val),
(G_LSHR $src, $rev, $amt):$mi,
(G_BITREVERSE $d, $src),
[{ return Helper.isLegalOrBeforeLegalizer({TargetOpcode::G_SHL,
{MRI.getType(${val}.getReg()),
MRI.getType(${amt}.getReg())}}); }]),
(apply (G_SHL $d, $val, $amt))>;

// Combine (shl (add x, c1), c2) -> (add (shl x, c2), c1 << c2)
// Combine (shl (or x, c1), c2) -> (or (shl x, c2), c1 << c2)
def commute_shift : GICombineRule<
Expand Down Expand Up @@ -1645,6 +1667,8 @@ def width_reduction_combines : GICombineGroup<[reduce_shl_of_extend,

def phi_combines : GICombineGroup<[extend_through_phis]>;

def bitreverse_shift : GICombineGroup<[bitreverse_shl, bitreverse_lshr]>;

def select_combines : GICombineGroup<[select_undef_cmp, select_constant_cmp,
match_selects]>;

Expand Down Expand Up @@ -1674,7 +1698,7 @@ def all_combines : GICombineGroup<[trivial_combines, vector_ops_combines,
unmerge_zext_to_zext, merge_unmerge, trunc_ext_fold, trunc_shift,
const_combines, xor_of_and_with_same_reg, ptr_add_with_zero,
shift_immed_chain, shift_of_shifted_logic_chain, load_or_combine,
div_rem_to_divrem, funnel_shift_combines, commute_shift,
div_rem_to_divrem, funnel_shift_combines, bitreverse_shift, commute_shift,
form_bitfield_extract, constant_fold_binops, constant_fold_fma,
constant_fold_cast_op, fabs_fneg_fold,
intdiv_combines, mulh_combines, redundant_neg_operands,
Expand Down
132 changes: 34 additions & 98 deletions llvm/test/CodeGen/AArch64/GlobalISel/combine-bitreverse-shift.ll
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=aarch64-unknown-unknown | FileCheck %s --check-prefixes=SDAG
; RUN: llc < %s -mtriple=aarch64-unknown-unknown -global-isel | FileCheck %s --check-prefixes=GISEL
; RUN: llc < %s -mtriple=aarch64-unknown-unknown | FileCheck %s
; RUN: llc < %s -mtriple=aarch64-unknown-unknown -global-isel | FileCheck %s

; These tests can be optimised
; fold (bitreverse(srl (bitreverse c), x)) -> (shl c, x)
Expand All @@ -12,151 +12,87 @@ declare i32 @llvm.bitreverse.i32(i32)
declare i64 @llvm.bitreverse.i64(i64)

define i8 @test_bitreverse_srli_bitreverse_i8(i8 %a) nounwind {
; SDAG-LABEL: test_bitreverse_srli_bitreverse_i8:
; SDAG: // %bb.0:
; SDAG-NEXT: lsl w0, w0, #3
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_srli_bitreverse_i8:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsr w8, w8, #24
; GISEL-NEXT: lsr w8, w8, #3
; GISEL-NEXT: rbit w8, w8
; GISEL-NEXT: lsr w0, w8, #24
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_srli_bitreverse_i8:
; CHECK: // %bb.0:
; CHECK-NEXT: lsl w0, w0, #3
; CHECK-NEXT: ret
%1 = call i8 @llvm.bitreverse.i8(i8 %a)
%2 = lshr i8 %1, 3
%3 = call i8 @llvm.bitreverse.i8(i8 %2)
ret i8 %3
}

define i16 @test_bitreverse_srli_bitreverse_i16(i16 %a) nounwind {
; SDAG-LABEL: test_bitreverse_srli_bitreverse_i16:
; SDAG: // %bb.0:
; SDAG-NEXT: lsl w0, w0, #7
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_srli_bitreverse_i16:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsr w8, w8, #16
; GISEL-NEXT: lsr w8, w8, #7
; GISEL-NEXT: rbit w8, w8
; GISEL-NEXT: lsr w0, w8, #16
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_srli_bitreverse_i16:
; CHECK: // %bb.0:
; CHECK-NEXT: lsl w0, w0, #7
; CHECK-NEXT: ret
%1 = call i16 @llvm.bitreverse.i16(i16 %a)
%2 = lshr i16 %1, 7
%3 = call i16 @llvm.bitreverse.i16(i16 %2)
ret i16 %3
}

define i32 @test_bitreverse_srli_bitreverse_i32(i32 %a) nounwind {
; SDAG-LABEL: test_bitreverse_srli_bitreverse_i32:
; SDAG: // %bb.0:
; SDAG-NEXT: lsl w0, w0, #15
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_srli_bitreverse_i32:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsr w8, w8, #15
; GISEL-NEXT: rbit w0, w8
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_srli_bitreverse_i32:
; CHECK: // %bb.0:
; CHECK-NEXT: lsl w0, w0, #15
; CHECK-NEXT: ret
%1 = call i32 @llvm.bitreverse.i32(i32 %a)
%2 = lshr i32 %1, 15
%3 = call i32 @llvm.bitreverse.i32(i32 %2)
ret i32 %3
}

define i64 @test_bitreverse_srli_bitreverse_i64(i64 %a) nounwind {
; SDAG-LABEL: test_bitreverse_srli_bitreverse_i64:
; SDAG: // %bb.0:
; SDAG-NEXT: lsl x0, x0, #33
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_srli_bitreverse_i64:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit x8, x0
; GISEL-NEXT: lsr x8, x8, #33
; GISEL-NEXT: rbit x0, x8
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_srli_bitreverse_i64:
; CHECK: // %bb.0:
; CHECK-NEXT: lsl x0, x0, #33
; CHECK-NEXT: ret
%1 = call i64 @llvm.bitreverse.i64(i64 %a)
%2 = lshr i64 %1, 33
%3 = call i64 @llvm.bitreverse.i64(i64 %2)
ret i64 %3
}

define i8 @test_bitreverse_shli_bitreverse_i8(i8 %a) nounwind {
; SDAG-LABEL: test_bitreverse_shli_bitreverse_i8:
; SDAG: // %bb.0:
; SDAG-NEXT: ubfx w0, w0, #3, #5
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_shli_bitreverse_i8:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsr w8, w8, #24
; GISEL-NEXT: lsl w8, w8, #3
; GISEL-NEXT: rbit w8, w8
; GISEL-NEXT: lsr w0, w8, #24
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_shli_bitreverse_i8:
; CHECK: // %bb.0:
; CHECK-NEXT: ubfx w0, w0, #3, #5
; CHECK-NEXT: ret
%1 = call i8 @llvm.bitreverse.i8(i8 %a)
%2 = shl i8 %1, 3
%3 = call i8 @llvm.bitreverse.i8(i8 %2)
ret i8 %3
}

define i16 @test_bitreverse_shli_bitreverse_i16(i16 %a) nounwind {
; SDAG-LABEL: test_bitreverse_shli_bitreverse_i16:
; SDAG: // %bb.0:
; SDAG-NEXT: ubfx w0, w0, #7, #9
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_shli_bitreverse_i16:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsr w8, w8, #16
; GISEL-NEXT: lsl w8, w8, #7
; GISEL-NEXT: rbit w8, w8
; GISEL-NEXT: lsr w0, w8, #16
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_shli_bitreverse_i16:
; CHECK: // %bb.0:
; CHECK-NEXT: ubfx w0, w0, #7, #9
; CHECK-NEXT: ret
%1 = call i16 @llvm.bitreverse.i16(i16 %a)
%2 = shl i16 %1, 7
%3 = call i16 @llvm.bitreverse.i16(i16 %2)
ret i16 %3
}

define i32 @test_bitreverse_shli_bitreverse_i32(i32 %a) nounwind {
; SDAG-LABEL: test_bitreverse_shli_bitreverse_i32:
; SDAG: // %bb.0:
; SDAG-NEXT: lsr w0, w0, #15
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_shli_bitreverse_i32:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit w8, w0
; GISEL-NEXT: lsl w8, w8, #15
; GISEL-NEXT: rbit w0, w8
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_shli_bitreverse_i32:
; CHECK: // %bb.0:
; CHECK-NEXT: lsr w0, w0, #15
; CHECK-NEXT: ret
%1 = call i32 @llvm.bitreverse.i32(i32 %a)
%2 = shl i32 %1, 15
%3 = call i32 @llvm.bitreverse.i32(i32 %2)
ret i32 %3
}

define i64 @test_bitreverse_shli_bitreverse_i64(i64 %a) nounwind {
; SDAG-LABEL: test_bitreverse_shli_bitreverse_i64:
; SDAG: // %bb.0:
; SDAG-NEXT: lsr x0, x0, #33
; SDAG-NEXT: ret
;
; GISEL-LABEL: test_bitreverse_shli_bitreverse_i64:
; GISEL: // %bb.0:
; GISEL-NEXT: rbit x8, x0
; GISEL-NEXT: lsl x8, x8, #33
; GISEL-NEXT: rbit x0, x8
; GISEL-NEXT: ret
; CHECK-LABEL: test_bitreverse_shli_bitreverse_i64:
; CHECK: // %bb.0:
; CHECK-NEXT: lsr x0, x0, #33
; CHECK-NEXT: ret
%1 = call i64 @llvm.bitreverse.i64(i64 %a)
%2 = shl i64 %1, 33
%3 = call i64 @llvm.bitreverse.i64(i64 %2)
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