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[MachinePipeliner] Fix store-store dependences (#72508) #72575

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merged 2 commits into from
Dec 12, 2023
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[MachinePipeliner] Fix store-store dependences (#72508) #72575

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23f5f59
[MachinePipeliner] Fix store-store dependences (#72508)
bcahoon Nov 16, 2023
3b821d2
Change isLoopCarriedDep to handle dependences with stores
bcahoon Nov 28, 2023
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8 changes: 5 additions & 3 deletions llvm/lib/CodeGen/MachinePipeliner.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2225,7 +2225,7 @@ MachineInstr *SwingSchedulerDAG::findDefInLoop(Register Reg) {
}

/// Return true for an order or output dependence that is loop carried
/// potentially. A dependence is loop carried if the destination defines a valu
/// potentially. A dependence is loop carried if the destination defines a value
/// that may be used or defined by the source in a subsequent iteration.
bool SwingSchedulerDAG::isLoopCarriedDep(SUnit *Source, const SDep &Dep,
bool isSucc) {
Expand All @@ -2251,10 +2251,12 @@ bool SwingSchedulerDAG::isLoopCarriedDep(SUnit *Source, const SDep &Dep,
SI->hasOrderedMemoryRef() || DI->hasOrderedMemoryRef())
return true;

// Only chain dependences between a load and store can be loop carried.
if (!DI->mayStore() || !SI->mayLoad())
if (!DI->mayLoadOrStore() || !SI->mayLoadOrStore())
return false;

// The conservative assumption is that a dependence between memory operations
// may be loop carried. The following code checks when it can be proved that
// there is no loop carried dependence.
unsigned DeltaS, DeltaD;
if (!computeDelta(*SI, DeltaS) || !computeDelta(*DI, DeltaD))
return true;
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84 changes: 84 additions & 0 deletions llvm/test/CodeGen/PowerPC/sms-store-dependence.ll
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@@ -0,0 +1,84 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 4
; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -verify-machineinstrs\
; RUN: -mcpu=pwr9 --ppc-enable-pipeliner 2>&1 | FileCheck %s

; Test that the pipeliner schedules the store instructions correctly. Since
; there is a dependence between the store, they cannot be scheduled further than
; MII cycles/instructions apart. That is, the first store cannot occur multiple
; times before the second ctore in the schedule.
define dso_local void @comp_method(ptr noalias nocapture noundef readonly %0, ptr nocapture noundef writeonly %1, ptr nocapture noundef writeonly %2, i32 noundef %3, i32 noundef %4, i32 noundef %5, i32 noundef %6, i64 %v1) local_unnamed_addr {
; CHECK-LABEL: comp_method:
; CHECK: # %bb.0:
; CHECK-NEXT: extsw 7, 8
; CHECK-NEXT: extsw 8, 9
; CHECK-NEXT: clrldi 9, 6, 32
; CHECK-NEXT: addi 6, 3, -1
; CHECK-NEXT: mtctr 9
; CHECK-NEXT: li 11, 0
; CHECK-NEXT: sradi 12, 11, 2
; CHECK-NEXT: add 5, 5, 8
; CHECK-NEXT: li 8, 2
; CHECK-NEXT: li 3, 8
; CHECK-NEXT: addi 11, 7, 0
; CHECK-NEXT: std 30, -16(1) # 8-byte Folded Spill
; CHECK-NEXT: lbzu 9, 1(6)
; CHECK-NEXT: add 12, 12, 10
; CHECK-NEXT: extsb 9, 9
; CHECK-NEXT: stbx 8, 4, 9
; CHECK-NEXT: add 9, 9, 12
; CHECK-NEXT: bdz .LBB0_2
; CHECK-NEXT: .p2align 4
; CHECK-NEXT: .LBB0_1:
; CHECK-NEXT: lbzu 0, 1(6)
; CHECK-NEXT: sradi 12, 11, 2
; CHECK-NEXT: add 11, 11, 7
; CHECK-NEXT: add 12, 12, 10
; CHECK-NEXT: sldi 30, 9, 2
; CHECK-NEXT: add 9, 9, 30
; CHECK-NEXT: extsb 0, 0
; CHECK-NEXT: stbx 3, 5, 9
; CHECK-NEXT: add 9, 0, 12
; CHECK-NEXT: stbx 8, 4, 0
; CHECK-NEXT: bdnz .LBB0_1
; CHECK-NEXT: .LBB0_2:
; CHECK-NEXT: sldi 4, 9, 2
; CHECK-NEXT: ld 30, -16(1) # 8-byte Folded Reload
; CHECK-NEXT: add 4, 9, 4
; CHECK-NEXT: stbx 3, 5, 4
; CHECK-NEXT: blr
%8 = icmp sgt i32 %3, 64
tail call void @llvm.assume(i1 %8)
%9 = and i32 %3, 1
%10 = icmp eq i32 %9, 0
tail call void @llvm.assume(i1 %10)
%11 = sext i32 %5 to i64
%12 = sext i32 %6 to i64
%13 = zext nneg i32 %3 to i64
%14 = getelementptr i8, ptr %2, i64 %12
br label %16

15:
ret void

16:
%17 = phi i64 [ 0, %7 ], [ %24, %16 ]
%18 = getelementptr inbounds i8, ptr %0, i64 %17
%19 = load i8, ptr %18, align 1
%20 = sext i8 %19 to i64
%21 = getelementptr inbounds i8, ptr %1, i64 %20
store i8 2, ptr %21, align 1
%22 = mul nsw i64 %17, %11
%a1 = ashr i64 %22, 2
%a2 = add i64 %a1, %v1
%a3 = add i64 %20, %a2
%a4 = mul nsw i64 %a3, 5
%23 = getelementptr i8, ptr %14, i64 %a4
store i8 8, ptr %23, align 1
%24 = add nuw nsw i64 %17, 1
%25 = icmp eq i64 %24, %13
br i1 %25, label %15, label %16
}

declare void @llvm.assume(i1 noundef) #1

attributes #1 = { mustprogress nocallback nofree nosync nounwind willreturn memory(inaccessiblemem: write) }