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[AArch64][GISel] and+or+shl => bfi
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This fixes a GISEL vs SDAG regression that showed up at -Os in 256.bzip2

In `_getAndMoveToFrontDecode`:

gisel:
```
and w9, w0, #0xff
orr w9, w9, w8, lsl rust-lang#8
```

sdag:
```
bfi w0, w8, rust-lang#8, rust-lang#24
```

Differential revision: https://reviews.llvm.org/D103291
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@jroelofs
jroelofs committed Jun 17, 2021
1 parent 9ac7388 commit 7b06120
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34 changes: 34 additions & 0 deletions llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2163,6 +2163,40 @@ bool AArch64InstructionSelector::earlySelect(MachineInstr &I) {
I.eraseFromParent();
return true;
}
case TargetOpcode::G_OR: {
// Look for operations that take the lower `Width=Size-ShiftImm` bits of
// `ShiftSrc` and insert them into the upper `Width` bits of `MaskSrc` via
// shifting and masking that we can replace with a BFI (encoded as a BFM).
Register Dst = I.getOperand(0).getReg();
LLT Ty = MRI.getType(Dst);

if (!Ty.isScalar())
return false;

unsigned Size = Ty.getSizeInBits();
if (Size != 32 && Size != 64)
return false;

Register ShiftSrc;
int64_t ShiftImm;
Register MaskSrc;
int64_t MaskImm;
if (!mi_match(
Dst, MRI,
m_GOr(m_OneNonDBGUse(m_GShl(m_Reg(ShiftSrc), m_ICst(ShiftImm))),
m_OneNonDBGUse(m_GAnd(m_Reg(MaskSrc), m_ICst(MaskImm))))))
return false;

if (ShiftImm > Size || ((1ULL << ShiftImm) - 1ULL) != uint64_t(MaskImm))
return false;

int64_t Immr = Size - ShiftImm;
int64_t Imms = Size - ShiftImm - 1;
unsigned Opc = Size == 32 ? AArch64::BFMWri : AArch64::BFMXri;
emitInstr(Opc, {Dst}, {MaskSrc, ShiftSrc, Immr, Imms}, MIB);
I.eraseFromParent();
return true;
}
default:
return false;
}
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157 changes: 157 additions & 0 deletions llvm/test/CodeGen/AArch64/GlobalISel/select-bitfield-insert.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,157 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -o - -verify-machineinstrs -global-isel=1 -global-isel-abort=1 | FileCheck %s --check-prefixes=CHECK,GISEL
; RUN: llc < %s -o - -verify-machineinstrs -global-isel=0 | FileCheck %s --check-prefixes=CHECK,SDAG

target datalayout = "e-m:o-i64:64-i128:128-n32:64-S128"
target triple = "arm64-apple-ios14.5.0"

define i32 @bfi_w_31(i32 %in1, i32 %in2) {
; CHECK-LABEL: bfi_w_31:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi w1, w0, #31, #1
; CHECK-NEXT: mov w0, w1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i32 %in1, 31
%tmp4 = and i32 %in2, 2147483647
%out = or i32 %tmp3, %tmp4
ret i32 %out
}

define i32 @bfi_w_8(i32 %in1, i32 %in2) {
; CHECK-LABEL: bfi_w_8:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi w1, w0, #8, #24
; CHECK-NEXT: mov w0, w1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i32 %in1, 8
%tmp4 = and i32 %in2, 255
%out = or i32 %tmp3, %tmp4
ret i32 %out
}

define i32 @bfi_w_1(i32 %in1, i32 %in2) {
; CHECK-LABEL: bfi_w_1:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi w1, w0, #1, #31
; CHECK-NEXT: mov w0, w1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i32 %in1, 1
%tmp4 = and i32 %in2, 1
%out = or i32 %tmp3, %tmp4
ret i32 %out
}

define i64 @bfi_x_63(i64 %in1, i64 %in2) {
; CHECK-LABEL: bfi_x_63:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi x1, x0, #63, #1
; CHECK-NEXT: mov x0, x1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 63
%tmp4 = and i64 %in2, 9223372036854775807
%out = or i64 %tmp3, %tmp4
ret i64 %out
}

define i64 @bfi_x_31(i64 %in1, i64 %in2) {
; CHECK-LABEL: bfi_x_31:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi x1, x0, #31, #33
; CHECK-NEXT: mov x0, x1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 31
%tmp4 = and i64 %in2, 2147483647
%out = or i64 %tmp3, %tmp4
ret i64 %out
}

define i64 @bfi_x_8(i64 %in1, i64 %in2) {
; CHECK-LABEL: bfi_x_8:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi x1, x0, #8, #56
; CHECK-NEXT: mov x0, x1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 8
%tmp4 = and i64 %in2, 255
%out = or i64 %tmp3, %tmp4
ret i64 %out
}

define i64 @bfi_x_1(i64 %in1, i64 %in2) {
; CHECK-LABEL: bfi_x_1:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi x1, x0, #1, #63
; CHECK-NEXT: mov x0, x1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 1
%tmp4 = and i64 %in2, 1
%out = or i64 %tmp3, %tmp4
ret i64 %out
}

define i64 @bfi_x_1_swapped(i64 %in1, i64 %in2) {
; CHECK-LABEL: bfi_x_1_swapped:
; CHECK: ; %bb.0: ; %bb
; CHECK-NEXT: bfi x1, x0, #1, #63
; CHECK-NEXT: mov x0, x1
; CHECK-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 1
%tmp4 = and i64 %in2, 1
%out = or i64 %tmp4, %tmp3
ret i64 %out
}

define i64 @extra_use1(i64 %in1, i64 %in2, i64* %p) {
; GISEL-LABEL: extra_use1:
; GISEL: ; %bb.0: ; %bb
; GISEL-NEXT: lsl x8, x0, #1
; GISEL-NEXT: and x9, x1, #0x1
; GISEL-NEXT: orr x0, x8, x9
; GISEL-NEXT: str x8, [x2]
; GISEL-NEXT: ret
;
; SDAG-LABEL: extra_use1:
; SDAG: ; %bb.0: ; %bb
; SDAG-NEXT: bfi x1, x0, #1, #63
; SDAG-NEXT: lsl x8, x0, #1
; SDAG-NEXT: mov x0, x1
; SDAG-NEXT: str x8, [x2]
; SDAG-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 1
%tmp4 = and i64 %in2, 1
%out = or i64 %tmp3, %tmp4
store i64 %tmp3, i64* %p
ret i64 %out
}

define i64 @extra_use2(i64 %in1, i64 %in2, i64* %p) {
; GISEL-LABEL: extra_use2:
; GISEL: ; %bb.0: ; %bb
; GISEL-NEXT: and x8, x1, #0x1
; GISEL-NEXT: orr x0, x8, x0, lsl #1
; GISEL-NEXT: str x8, [x2]
; GISEL-NEXT: ret
;
; SDAG-LABEL: extra_use2:
; SDAG: ; %bb.0: ; %bb
; SDAG-NEXT: and x8, x1, #0x1
; SDAG-NEXT: bfi x1, x0, #1, #63
; SDAG-NEXT: mov x0, x1
; SDAG-NEXT: str x8, [x2]
; SDAG-NEXT: ret
bb:
%tmp3 = shl i64 %in1, 1
%tmp4 = and i64 %in2, 1
%out = or i64 %tmp3, %tmp4
store i64 %tmp4, i64* %p
ret i64 %out
}

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