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[ARM] Preserve liveness in ARMConstantIslands. 

We currently don't use liveness information after this point, but it can
be useful to catch bugs using -verify-machineinstrs, and optimizations
could potentially use this information in the future.

Differential Revision: https://reviews.llvm.org/D66319

llvm-svn: 369162
This commit is contained in:
Eli Friedman 2019-08-16 22:20:14 +00:00
parent 87869b398d
commit eaff844fe9
2 changed files with 26 additions and 3 deletions
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21
llvm/lib/Target/ARM/ARMConstantIslandPass.cpp
View File

@ -26,6 +26,7 @@
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/CodeGen/LivePhysRegs.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineConstantPool.h"
#include "llvm/CodeGen/MachineFunction.h"
@ -357,9 +358,6 @@ bool ARMConstantIslands::runOnMachineFunction(MachineFunction &mf) {
HasFarJump = false;
bool GenerateTBB = isThumb2 || (isThumb1 && SynthesizeThumb1TBB);
// This pass invalidates liveness information when it splits basic blocks.
MF->getRegInfo().invalidateLiveness();
// Renumber all of the machine basic blocks in the function, guaranteeing that
// the numbers agree with the position of the block in the function.
MF->RenumberBlocks();
@ -880,6 +878,13 @@ void ARMConstantIslands::updateForInsertedWaterBlock(MachineBasicBlock *NewBB) {
MachineBasicBlock *ARMConstantIslands::splitBlockBeforeInstr(MachineInstr *MI) {
MachineBasicBlock *OrigBB = MI->getParent();
// Collect liveness information at MI.
LivePhysRegs LRs(*MF->getSubtarget().getRegisterInfo());
LRs.addLiveOuts(*OrigBB);
auto LivenessEnd = ++MachineBasicBlock::iterator(MI).getReverse();
for (MachineInstr &LiveMI : make_range(OrigBB->rbegin(), LivenessEnd))
LRs.stepBackward(LiveMI);
// Create a new MBB for the code after the OrigBB.
MachineBasicBlock *NewBB =
MF->CreateMachineBasicBlock(OrigBB->getBasicBlock());
@ -908,6 +913,12 @@ MachineBasicBlock *ARMConstantIslands::splitBlockBeforeInstr(MachineInstr *MI) {
// OrigBB branches to NewBB.
OrigBB->addSuccessor(NewBB);
// Update live-in information in the new block.
MachineRegisterInfo &MRI = MF->getRegInfo();
for (MCPhysReg L : LRs)
if (!MRI.isReserved(L))
NewBB->addLiveIn(L);
// Update internal data structures to account for the newly inserted MBB.
// This is almost the same as updateForInsertedWaterBlock, except that
// the Water goes after OrigBB, not NewBB.
@ -2331,6 +2342,10 @@ adjustJTTargetBlockForward(MachineBasicBlock *BB, MachineBasicBlock *JTBB) {
MachineFunction::iterator MBBI = ++JTBB->getIterator();
MF->insert(MBBI, NewBB);
// Copy live-in information to new block.
for (const MachineBasicBlock::RegisterMaskPair &RegMaskPair : BB->liveins())
NewBB->addLiveIn(RegMaskPair);
// Add an unconditional branch from NewBB to BB.
// There doesn't seem to be meaningful DebugInfo available; this doesn't
// correspond directly to anything in the source.

8
llvm/test/CodeGen/ARM/constant-island-movwt.mir
View File

@ -898,5 +898,13 @@ body: |
# CHECK-NEXT: CONSTPOOL_ENTRY 1, %const.0, 4
# CHECK-NEXT: {{^ $}}
# CHECK-NEXT: bb.2.entry (align 1):
# CHECK-NEXT: liveins: $d13, $s27, $r10, $r9, $r8, $s26, $d12, $s25, $s24,
# CHECK-SAME: $d15, $s30, $s31, $d14, $s28, $s29, $lr, $r0, $d21,
# CHECK-SAME: $r3, $q10, $d20, $d17, $r2, $d25, $q11, $d22, $d23,
# CHECK-SAME: $r1, $q8, $d16, $s3, $q14, $d28, $d29, $d19, $s17,
# CHECK-SAME: $d8, $s16, $r6, $r7, $r4, $q12, $q9, $d18, $s0, $q15,
# CHECK-SAME: $d30, $d31, $r12, $s1, $d0, $d24, $s2, $d1, $q0, $s6,
# CHECK-SAME: $d3, $d2, $s4, $q1, $s7, $s5, $d9, $s18, $s19, $q4
# CHECK-NEXT: {{^ $}}
# CHECK-NEXT: $r5 = t2MOVi16 target-flags(arm-lo16) @.str.84, 14, $noreg
# CHECK-NEXT: $r5 = t2MOVTi16 $r5, target-flags(arm-hi16) @.str.84, 14, $noreg