Commit 43ba9d9f authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r324422: 

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r324422 | efriedma | 2018-02-07 00:00:17 +0100 (Wed, 07 Feb 2018) | 16 lines

[LivePhysRegs] Fix handling of return instructions.

See D42509 for the original version of this.

Basically, there are two significant changes to behavior here:

- addLiveOuts always adds all pristine registers (even if a block has
no successors).
- addLiveOuts and addLiveOutsNoPristines always add all callee-saved
registers for return blocks (including conditional return blocks).

I cleaned up the functions a bit to make it clear these properties hold.

Differential Revision: https://reviews.llvm.org/D42655


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llvm-svn: 324466
parent 0e83d687

llvm/lib/CodeGen/LivePhysRegs.cpp

+14 −17
Original line number Diff line number Diff line
@@ -205,14 +205,18 @@ void LivePhysRegs::addPristines(const MachineFunction &MF) { 
}



void LivePhysRegs::addLiveOutsNoPristines(const MachineBasicBlock &MBB) {

  if (!MBB.succ_empty()) {

  // To get the live-outs we simply merge the live-ins of all successors.

  for (const MachineBasicBlock *Succ : MBB.successors())

    addBlockLiveIns(*Succ);

  } else if (MBB.isReturnBlock()) {

    // For the return block: Add all callee saved registers that are saved and

    // restored (somewhere); This does not include callee saved registers that

    // are unused and hence not saved and restored; they are called pristine.

  if (MBB.isReturnBlock()) {

    // Return blocks are a special case because we currently don't mark up

    // return instructions completely: specifically, there is no explicit

    // use for callee-saved registers. So we add all callee saved registers

    // that are saved and restored (somewhere). This does not include

    // callee saved registers that are unused and hence not saved and

    // restored; they are called pristine.

    // FIXME: PEI should add explicit markings to return instructions

    // instead of implicitly handling them here.

    const MachineFunction &MF = *MBB.getParent();

    const MachineFrameInfo &MFI = MF.getFrameInfo();

    if (MFI.isCalleeSavedInfoValid()) {
@@ -225,15 +229,8 @@ void LivePhysRegs::addLiveOutsNoPristines(const MachineBasicBlock &MBB) { 


void LivePhysRegs::addLiveOuts(const MachineBasicBlock &MBB) {

  const MachineFunction &MF = *MBB.getParent();

  if (!MBB.succ_empty()) {

  addPristines(MF);

  addLiveOutsNoPristines(MBB);

  } else if (MBB.isReturnBlock()) {

    // For the return block: Add all callee saved registers.

    const MachineFrameInfo &MFI = MF.getFrameInfo();

    if (MFI.isCalleeSavedInfoValid())

      addCalleeSavedRegs(*this, MF);

  }

}



void LivePhysRegs::addLiveIns(const MachineBasicBlock &MBB) {

llvm/test/CodeGen/ARM/pr25838.ll

+1 −1
Original line number Diff line number Diff line 
; RUN: llc < %s

; RUN: llc -verify-machineinstrs < %s

; PR25838



target triple = "armv7--linux-android"

llvm/test/CodeGen/Thumb/stm-scavenging.ll

0 → 100644
+46 −0
Original line number Diff line number Diff line 
; RUN: llc < %s | FileCheck %s

target triple = "thumbv6---gnueabi"



; Use STM to save the three registers

; CHECK-LABEL: use_stm:

; CHECK: .save   {r7, lr}

; CHECK: .setfp  r7, sp

; CHECK: stm r3!, {r0, r1, r2}

; CHECK: bl throws_1

define void @use_stm(i32 %a, i32 %b, i32 %c, i32* %d) local_unnamed_addr noreturn "no-frame-pointer-elim"="true" {

entry:

  %arrayidx = getelementptr inbounds i32, i32* %d, i32 2

  store i32 %a, i32* %arrayidx, align 4

  %arrayidx1 = getelementptr inbounds i32, i32* %d, i32 3

  store i32 %b, i32* %arrayidx1, align 4

  %arrayidx2 = getelementptr inbounds i32, i32* %d, i32 4

  store i32 %c, i32* %arrayidx2, align 4

  tail call void @throws_1(i32 %a, i32 %b, i32 %c) noreturn

  unreachable

}



; Don't use STM: there is no available register to store

; the address. We could transform this with some extra math, but

; that currently isn't implemented.

; CHECK-LABEL: no_stm:

; CHECK: .save   {r7, lr}

; CHECK: .setfp  r7, sp

; CHECK: str r0,

; CHECK: str r1,

; CHECK: str r2,

; CHECK: bl throws_2

define void @no_stm(i32 %a, i32 %b, i32 %c, i32* %d) local_unnamed_addr noreturn "no-frame-pointer-elim"="true" {

entry:

  %arrayidx = getelementptr inbounds i32, i32* %d, i32 2

  store i32 %a, i32* %arrayidx, align 4

  %arrayidx1 = getelementptr inbounds i32, i32* %d, i32 3

  store i32 %b, i32* %arrayidx1, align 4

  %arrayidx2 = getelementptr inbounds i32, i32* %d, i32 4

  store i32 %c, i32* %arrayidx2, align 4

  tail call void @throws_2(i32 %a, i32 %b, i32 %c, i32* %d) noreturn

  unreachable

}





declare void @throws_1(i32, i32, i32) noreturn

declare void @throws_2(i32, i32, i32, i32*) noreturn