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[DAGCombiner] Rebuild (setcc x, y, ==) from (xor (xor x, y), 1)
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The existing code already considered this case. Unfortunately a typo in
the condition prevents it from triggering. Also the existing code, had
it run, forgot to do the folding.

This fixes PR42876.

Differential Revision: https://reviews.llvm.org/D65802
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@rofirrim
rofirrim committed Jul 15, 2020
1 parent 2b6215f commit 14bc5e1
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Showing 6 changed files with 31 additions and 43 deletions.
21 changes: 11 additions & 10 deletions llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14099,8 +14099,8 @@ SDValue DAGCombiner::rebuildSetCC(SDValue N) {
}
}

// Transform br(xor(x, y)) -> br(x != y)
// Transform br(xor(xor(x,y), 1)) -> br (x == y)
// Transform (brcond (xor x, y)) -> (brcond (setcc, x, y, ne))
// Transform (brcond (xor (xor x, y), -1)) -> (brcond (setcc, x, y, eq))
if (N.getOpcode() == ISD::XOR) {
// Because we may call this on a speculatively constructed
// SimplifiedSetCC Node, we need to simplify this node first.
Expand All @@ -14124,24 +14124,25 @@ SDValue DAGCombiner::rebuildSetCC(SDValue N) {
if (N.getOpcode() != ISD::XOR)
return N;

SDNode *TheXor = N.getNode();

SDValue Op0 = TheXor->getOperand(0);
SDValue Op1 = TheXor->getOperand(1);
SDValue Op0 = N->getOperand(0);
SDValue Op1 = N->getOperand(1);

if (Op0.getOpcode() != ISD::SETCC && Op1.getOpcode() != ISD::SETCC) {
bool Equal = false;
if (isOneConstant(Op0) && Op0.hasOneUse() &&
Op0.getOpcode() == ISD::XOR) {
TheXor = Op0.getNode();
// (brcond (xor (xor x, y), -1)) -> (brcond (setcc x, y, eq))
if (isBitwiseNot(N) && Op0.hasOneUse() && Op0.getOpcode() == ISD::XOR &&
Op0.getValueType() == MVT::i1) {
N = Op0;
Op0 = N->getOperand(0);
Op1 = N->getOperand(1);
Equal = true;
}

EVT SetCCVT = N.getValueType();
if (LegalTypes)
SetCCVT = getSetCCResultType(SetCCVT);
// Replace the uses of XOR with SETCC
return DAG.getSetCC(SDLoc(TheXor), SetCCVT, Op0, Op1,
return DAG.getSetCC(SDLoc(N), SetCCVT, Op0, Op1,
Equal ? ISD::SETEQ : ISD::SETNE);
}
}
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5 changes: 2 additions & 3 deletions llvm/test/CodeGen/AArch64/cmp-bool.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -25,9 +25,8 @@ if.end:
define void @bool_ne(i1 zeroext %a, i1 zeroext %b, void ()* nocapture %c) nounwind {
; CHECK-LABEL: bool_ne:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: eor w8, w0, w1
; CHECK-NEXT: cmp w8, #1 // =1
; CHECK-NEXT: b.ne .LBB1_2
; CHECK-NEXT: cmp w0, w1
; CHECK-NEXT: b.eq .LBB1_2
; CHECK-NEXT: // %bb.1: // %if.then
; CHECK-NEXT: br x2
; CHECK-NEXT: .LBB1_2: // %if.end
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17 changes: 7 additions & 10 deletions llvm/test/CodeGen/ARM/cmp-bool.ll
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Expand Up @@ -41,28 +41,25 @@ if.end:
define void @bool_ne(i1 zeroext %a, i1 zeroext %b, void ()* nocapture %c) nounwind {
; ARM-LABEL: bool_ne:
; ARM: @ %bb.0: @ %entry
; ARM-NEXT: eor r0, r0, r1
; ARM-NEXT: cmp r0, #1
; ARM-NEXT: bxne lr
; ARM-NEXT: cmp r0, r1
; ARM-NEXT: bxeq lr
; ARM-NEXT: bx r2
;
; THUMB-LABEL: bool_ne:
; THUMB: @ %bb.0: @ %entry
; THUMB-NEXT: push {r7, lr}
; THUMB-NEXT: eors r0, r1
; THUMB-NEXT: cmp r0, #1
; THUMB-NEXT: bne .LBB1_2
; THUMB-NEXT: cmp r0, r1
; THUMB-NEXT: beq .LBB1_2
; THUMB-NEXT: @ %bb.1: @ %if.then
; THUMB-NEXT: blx r2
; THUMB-NEXT: .LBB1_2: @ %if.end
; THUMB-NEXT: pop {r7, pc}
;
; THUMB2-LABEL: bool_ne:
; THUMB2: @ %bb.0: @ %entry
; THUMB2-NEXT: eors r0, r1
; THUMB2-NEXT: cmp r0, #1
; THUMB2-NEXT: it ne
; THUMB2-NEXT: bxne lr
; THUMB2-NEXT: cmp r0, r1
; THUMB2-NEXT: it eq
; THUMB2-NEXT: bxeq lr
; THUMB2-NEXT: bx r2
entry:
%cmp = xor i1 %a, %b
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8 changes: 2 additions & 6 deletions llvm/test/CodeGen/RISCV/cmp-bool.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -33,19 +33,15 @@ if.end:
define void @bool_ne(i1 zeroext %a, i1 zeroext %b, void ()* nocapture %c) nounwind {
; RV32-LABEL: bool_ne:
; RV32: # %bb.0: # %entry
; RV32-NEXT: xor a0, a0, a1
; RV32-NEXT: addi a1, zero, 1
; RV32-NEXT: bne a0, a1, .LBB1_2
; RV32-NEXT: beq a0, a1, .LBB1_2
; RV32-NEXT: # %bb.1: # %if.then
; RV32-NEXT: jr a2
; RV32-NEXT: .LBB1_2: # %if.end
; RV32-NEXT: ret
;
; RV64-LABEL: bool_ne:
; RV64: # %bb.0: # %entry
; RV64-NEXT: xor a0, a0, a1
; RV64-NEXT: addi a1, zero, 1
; RV64-NEXT: bne a0, a1, .LBB1_2
; RV64-NEXT: beq a0, a1, .LBB1_2
; RV64-NEXT: # %bb.1: # %if.then
; RV64-NEXT: jr a2
; RV64-NEXT: .LBB1_2: # %if.end
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18 changes: 7 additions & 11 deletions llvm/test/CodeGen/WebAssembly/reg-stackify.ll
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Expand Up @@ -112,16 +112,14 @@ define i32 @no_sink_readonly_call(i32 %x, i32 %y, i32* %p) {
; CHECK-NEXT: i32.const $push[[L11:[0-9]+]]=, 2{{$}}
; CHECK-NEXT: i32.lt_s $push[[L4:[0-9]+]]=, $3, $pop[[L11]]{{$}}
; CHECK-NEXT: i32.xor $push[[L6:[0-9]+]]=, $pop[[L3]], $pop[[L4]]{{$}}
; CHECK-NEXT: i32.xor $push[[L7:[0-9]+]]=, $pop[[L5]], $pop[[L6]]{{$}}
; CHECK-NEXT: i32.const $push10=, 1{{$}}
; CHECK-NEXT: i32.ne $push8=, $pop7, $pop10{{$}}
; CHECK-NEXT: br_if 0, $pop8{{$}}
; CHECK-NEXT: i32.const $push9=, 0{{$}}
; CHECK-NEXT: return $pop9{{$}}
; CHECK-NEXT: i32.eq $push7=, $pop[[L5]], $pop[[L6]]{{$}}
; CHECK-NEXT: br_if 0, $pop7{{$}}
; CHECK-NEXT: i32.const $push8=, 0{{$}}
; CHECK-NEXT: return $pop8{{$}}
; CHECK-NEXT: .LBB{{[0-9]+}}_2:
; CHECK-NEXT: end_block{{$}}
; CHECK-NEXT: i32.const $push14=, 1{{$}}
; CHECK-NEXT: return $pop14{{$}}
; CHECK-NEXT: i32.const $push12=, 1{{$}}
; CHECK-NEXT: return $pop12{{$}}
; NOREGS-LABEL: stack_uses:
; NOREGS: .functype stack_uses (i32, i32, i32, i32) -> (i32){{$}}
; NOREGS-NEXT: block {{$}}
Expand All @@ -139,9 +137,7 @@ define i32 @no_sink_readonly_call(i32 %x, i32 %y, i32* %p) {
; NOREGS-NEXT: i32.const 2{{$}}
; NOREGS-NEXT: i32.lt_s
; NOREGS-NEXT: i32.xor {{$}}
; NOREGS-NEXT: i32.xor {{$}}
; NOREGS-NEXT: i32.const 1{{$}}
; NOREGS-NEXT: i32.ne {{$}}
; NOREGS-NEXT: i32.eq {{$}}
; NOREGS-NEXT: br_if 0{{$}}
; NOREGS-NEXT: i32.const 0{{$}}
; NOREGS-NEXT: return{{$}}
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5 changes: 2 additions & 3 deletions llvm/test/CodeGen/X86/cmp-bool.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -25,9 +25,8 @@ if.end:
define void @bool_ne(i1 zeroext %a, i1 zeroext %b, void ()* nocapture %c) nounwind {
; CHECK-LABEL: bool_ne:
; CHECK: # %bb.0: # %entry
; CHECK-NEXT: xorl %esi, %edi
; CHECK-NEXT: cmpb $1, %dil
; CHECK-NEXT: jne .LBB1_1
; CHECK-NEXT: cmpb %sil, %dil
; CHECK-NEXT: je .LBB1_1
; CHECK-NEXT: # %bb.2: # %if.then
; CHECK-NEXT: jmpq *%rdx # TAILCALL
; CHECK-NEXT: .LBB1_1: # %if.end
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