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[MachineOutliner][AArch64] Improve checks for stack instructions
If we know that we'll definitely save LR to a register, there's no reason to pre-check whether or not a stack instruction is unsafe to fix up. This makes it so that we check for that condition before mapping instructions. This allows us to outline more, since we don't pessimise as many instructions. Also update some tests, since we outline more. llvm-svn: 348081
This commit is contained in:
Jessica Paquette
parent
2fa8070014
commit
c877e03376
@ -5284,7 +5284,29 @@ bool AArch64InstrInfo::isMBBSafeToOutlineFrom(MachineBasicBlock &MBB,
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if (any_of(MBB, [](MachineInstr &MI) { return MI.isCall(); }))
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Flags |= MachineOutlinerMBBFlags::HasCalls;
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if (!LRU.available(AArch64::LR))
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MachineFunction *MF = MBB.getParent();
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// In the event that we outline, we may have to save LR. If there is an
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// available register in the MBB, then we'll always save LR there. Check if
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// this is true.
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bool CanSaveLR = false;
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const AArch64RegisterInfo *ARI = static_cast<const AArch64RegisterInfo *>(
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MF->getSubtarget().getRegisterInfo());
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// Check if there is an available register across the sequence that we can
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// use.
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for (unsigned Reg : AArch64::GPR64RegClass) {
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if (!ARI->isReservedReg(*MF, Reg) && Reg != AArch64::LR &&
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Reg != AArch64::X16 && Reg != AArch64::X17 && LRU.available(Reg)) {
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CanSaveLR = true;
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break;
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}
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}
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// Check if we have a register we can save LR to, and if LR was used
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// somewhere. If both of those things are true, then we need to evaluate the
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// safety of outlining stack instructions later.
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if (!CanSaveLR && !LRU.available(AArch64::LR))
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Flags |= MachineOutlinerMBBFlags::LRUnavailableSomewhere;
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return true;
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@ -1,10 +1,10 @@
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; RUN: llc %s -enable-machine-outliner -mtriple=aarch64-unknown-unknown -pass-remarks=machine-outliner -pass-remarks-missed=machine-outliner -o /dev/null 2>&1 | FileCheck %s
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; CHECK: <unknown>:0:0:
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; CHECK-SAME: Did not outline 2 instructions from 2 locations.
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; CHECK-SAME: Bytes from outlining all occurrences (36) >=
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; CHECK-SAME: Bytes from outlining all occurrences (16) >=
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; CHECK-SAME: Unoutlined instruction bytes (16)
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; CHECK-SAME: (Also found at: <UNKNOWN LOCATION>)
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; CHECK: remark: <unknown>:0:0: Saved 20 bytes by outlining 12 instructions
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; CHECK: remark: <unknown>:0:0: Saved 48 bytes by outlining 14 instructions
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; CHECK-SAME: from 2 locations. (Found at: <UNKNOWN LOCATION>,
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; CHECK-SAME: <UNKNOWN LOCATION>)
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; RUN: llc %s -enable-machine-outliner -mtriple=aarch64-unknown-unknown -o /dev/null -pass-remarks-missed=machine-outliner -pass-remarks-output=%t.yaml
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@ -16,7 +16,7 @@
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; YAML-NEXT: Pass: machine-outliner
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; YAML-NEXT: Name: NotOutliningCheaper
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; YAML-NEXT: Function:
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; YAML-NEXT: Args:
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; YAML-NEXT: Args:
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; YAML-NEXT: - String: 'Did not outline '
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; YAML-NEXT: - Length: '2'
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; YAML-NEXT: - String: ' instructions'
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@ -24,7 +24,7 @@
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; YAML-NEXT: - NumOccurrences: '2'
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; YAML-NEXT: - String: ' locations.'
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; YAML-NEXT: - String: ' Bytes from outlining all occurrences ('
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; YAML-NEXT: - OutliningCost: '36'
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; YAML-NEXT: - OutliningCost: '16'
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; YAML-NEXT: - String: ')'
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; YAML-NEXT: - String: ' >= Unoutlined instruction bytes ('
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; YAML-NEXT: - NotOutliningCost: '16'
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@ -36,12 +36,12 @@
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; YAML-NEXT: Pass: machine-outliner
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; YAML-NEXT: Name: OutlinedFunction
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; YAML-NEXT: Function: OUTLINED_FUNCTION_0
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; YAML-NEXT: Args:
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; YAML-NEXT: Args:
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; YAML-NEXT: - String: 'Saved '
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; YAML-NEXT: - OutliningBenefit: '20'
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; YAML-NEXT: - OutliningBenefit: '48'
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; YAML-NEXT: - String: ' bytes by '
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; YAML-NEXT: - String: 'outlining '
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; YAML-NEXT: - Length: '12'
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; YAML-NEXT: - Length: '14'
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; YAML-NEXT: - String: ' instructions '
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; YAML-NEXT: - String: 'from '
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; YAML-NEXT: - NumOccurrences: '2'
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@ -103,6 +103,7 @@ define void @dog() #0 {
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; CHECK-NEXT: str w8, [sp, #12]
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; CHECK-NEXT: orr w8, wzr, #0x6
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; CHECK-NEXT: str w8, [sp, #8]
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; CHECK-NEXT: add sp, sp, #32
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; CHECK-NEXT: ret
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attributes #0 = { noredzone "target-cpu"="cyclone" "target-features"="+sse" }
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@ -22,39 +22,39 @@
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# - Create outlined functions
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# - Don't outline anything to do with LR or W30
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# - Save LR when it's not available
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# - Don't outline stack instructions when we might need to save + restore
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# - Functions whose addresses are taken can still be outlined
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#
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# CHECK-LABEL: name: main
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# CHECK: BL @OUTLINED_FUNCTION_[[F0:[0-9]+]]
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# CHECK-LABEL: main
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# CHECK-LABEL: bb.1:
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# CHECK-DAG: BL @OUTLINED_FUNCTION_[[F0:[0-9]+]]
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# CHECK-NEXT: $lr = ORRXrs $xzr, $x[[REG:[0-9]+]], 0
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# CHECK-NEXT: $x12 = ADDXri $sp, 48, 0
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# CHECK-NEXT: STRHHroW $w12, $x9, $w30, 1, 1
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# CHECK-NEXT: $lr = ORRXri $xzr, 1
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# CHECK-DAG: bb.2
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# CHECK: BL @OUTLINED_FUNCTION_[[F0]]
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# CHECK-NEXT: $lr = ORRXrs $xzr, $x[[REG]], 0
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# CHECK-NEXT: $x12 = ADDXri $sp, 48, 0
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# CHECK-NEXT: STRHHroW $w12, $x9, $w30, 1, 1
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# CHECK-NEXT: $lr = ORRXri $xzr, 1
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# CHECK-DAG: bb.3
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# CHECK: BL @OUTLINED_FUNCTION_[[F0]]
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# CHECK-NEXT: $lr = ORRXrs $xzr, $x[[REG]], 0
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# CHECK-NEXT: $x12 = ADDXri $sp, 48, 0
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# CHECK-NEXT: STRHHroW $w12, $x9, $w30, 1, 1
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# CHECK-NEXT: $lr = ORRXri $xzr, 1
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name: main
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tracksRegLiveness: true
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body: |
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bb.0:
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liveins: $lr
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$sp = frame-setup SUBXri $sp, 16, 0
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renamable $x9 = ADRP target-flags(aarch64-page) @bar
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$x9 = ORRXri $xzr, 1
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$w12 = ORRWri $wzr, 1
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$w30 = ORRWri $wzr, 1
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$lr = ORRXri $xzr, 1
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bb.1:
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liveins: $lr
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$x20, $x19 = LDPXi $sp, 10
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$w12 = ORRWri $wzr, 1
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$w12 = ORRWri $wzr, 1
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@ -66,8 +66,8 @@ body: |
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$x12 = ADDXri $sp, 48, 0;
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STRHHroW $w12, $x9, $w30, 1, 1
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$lr = ORRXri $xzr, 1
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$w3 = ORRWri $wzr, 1993
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bb.2:
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liveins: $lr
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$x20, $x19 = LDPXi $sp, 10
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$w12 = ORRWri $wzr, 1
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$w12 = ORRWri $wzr, 1
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@ -79,9 +79,8 @@ body: |
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$x12 = ADDXri $sp, 48, 0;
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STRHHroW $w12, $x9, $w30, 1, 1
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$lr = ORRXri $xzr, 1
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$w4 = ORRWri $wzr, 1994
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bb.3:
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liveins: $lr
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$x20, $x19 = LDPXi $sp, 10
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$w12 = ORRWri $wzr, 1
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$w12 = ORRWri $wzr, 1
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@ -93,8 +92,9 @@ body: |
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$x12 = ADDXri $sp, 48, 0;
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STRHHroW $w12, $x9, $w30, 1, 1
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$lr = ORRXri $xzr, 1
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$sp = ADDXri $sp, 16, 0
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bb.4:
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liveins: $lr
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RET undef $lr
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...
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