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[AArch64] Don't try to sink and(load) #122274

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Merged
merged 2 commits into from
Jan 10, 2025
Merged

[AArch64] Don't try to sink and(load) #122274

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6d45baf
[AArch64] Don't try to sink and(load)
davemgreen Jan 9, 2025
e295a9f
Address some super nitpicky nits
davemgreen Jan 10, 2025
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5 changes: 4 additions & 1 deletion llvm/lib/Target/AArch64/AArch64TargetTransformInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5514,7 +5514,10 @@ bool AArch64TTIImpl::isProfitableToSinkOperands(
NumZExts++;
}

Ops.push_back(&Insert->getOperandUse(1));
// And(Load) is excluded to prevent CGP getting stuck in a loop of sinking
// the And, just to hoist it again back to the load.
if (!match(OperandInstr, m_And(m_Load(m_Value()), m_Value())))
Ops.push_back(&Insert->getOperandUse(1));
Ops.push_back(&Shuffle->getOperandUse(0));
Ops.push_back(&Op);
}
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50 changes: 48 additions & 2 deletions llvm/test/CodeGen/AArch64/aarch64-dup-ext-crash.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ target triple = "aarch64-unknown-linux-gnu"
; here, only that this case no longer causes said crash.
define dso_local i32 @dupext_crashtest(i32 %e) local_unnamed_addr {
; CHECK-LABEL: dupext_crashtest:
; CHECK: // %bb.0: // %for.body.lr.ph
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: dup v0.2s, w0
; CHECK-NEXT: .LBB0_1: // %vector.body
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
Expand All @@ -18,7 +18,7 @@ define dso_local i32 @dupext_crashtest(i32 %e) local_unnamed_addr {
; CHECK-NEXT: xtn v1.2s, v1.2d
; CHECK-NEXT: str d1, [x8]
; CHECK-NEXT: b .LBB0_1
for.body.lr.ph:
entry:
%conv314 = zext i32 %e to i64
br label %vector.memcheck

Expand All @@ -40,3 +40,49 @@ vector.body: ; preds = %vector.body, %vecto
store <2 x i32> %3, ptr %4, align 4
br label %vector.body
}

; This test got stuck in a loop hoisting the and to the load, and sinking it back to the mull
define i32 @dup_and_load(ptr %p, i1 %c) {
; CHECK-LABEL: dup_and_load:
; CHECK: // %bb.0: // %entry
; CHECK-NEXT: mov x8, x0
; CHECK-NEXT: ldrb w0, [x0]
; CHECK-NEXT: tbz w1, #0, .LBB1_3
; CHECK-NEXT: // %bb.1: // %ph
; CHECK-NEXT: dup v0.8h, w0
; CHECK-NEXT: mov w9, wzr
; CHECK-NEXT: .LBB1_2: // %vector.body
; CHECK-NEXT: // =>This Inner Loop Header: Depth=1
; CHECK-NEXT: ldr d1, [x8]
; CHECK-NEXT: add w9, w9, #1
; CHECK-NEXT: cmp w9, #100
; CHECK-NEXT: ushll v1.8h, v1.8b, #0
; CHECK-NEXT: umull2 v2.4s, v0.8h, v1.8h
; CHECK-NEXT: umull v1.4s, v0.4h, v1.4h
; CHECK-NEXT: stp q1, q2, [x8]
; CHECK-NEXT: b.lt .LBB1_2
; CHECK-NEXT: .LBB1_3: // %end
; CHECK-NEXT: ret
entry:
%l = load i32, ptr %p
%and255 = and i32 %l, 255
br i1 %c, label %ph, label %end

ph:
%broadcast.splatinsert = insertelement <8 x i32> poison, i32 %and255, i32 0
%broadcast.splat = shufflevector <8 x i32> %broadcast.splatinsert, <8 x i32> poison, <8 x i32> zeroinitializer
br label %vector.body

vector.body: ; preds = %vector.body, %vector.ph
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@david-arm david-arm Jan 9, 2025

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Does this need to be a loop in order to trigger the crash? Just wondering if it could be a normal block to reduce the lines of IR.

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@davemgreen davemgreen Jan 10, 2025

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I think it is OK - it was copied from the test above and modified enough to trigger the issue.

%iv = phi i32 [ 0, %ph ], [ %iv.next, %vector.body ]
%wide.load = load <8 x i8>, ptr %p, align 4
%0 = zext <8 x i8> %wide.load to <8 x i32>
%1 = mul <8 x i32> %broadcast.splat, %0
store <8 x i32> %1, ptr %p, align 4
%iv.next = add i32 %iv, 1
%e = icmp slt i32 %iv.next, 100
br i1 %e, label %vector.body, label %end

end:
ret i32 %and255
}
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