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[ARM] Remove a dead ADD during the creation of TBBs
During the optimisation of jump tables in the constant island pass, an extra ADD could be left over, now dead but not removed. Differential Revision: https://reviews.llvm.org/D31389 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@299634 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
David Green
parent
3c3df0d82a
commit
3b23ff5204
@ -2017,6 +2017,44 @@ static bool jumpTableFollowsTB(MachineInstr *JTMI, MachineInstr *CPEMI) {
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&*MBB->begin() == CPEMI;
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}
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static void RemoveDeadAddBetweenLEAAndJT(MachineInstr *LEAMI,
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MachineInstr *JumpMI,
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unsigned &DeadSize) {
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// Remove a dead add between the LEA and JT, which used to compute EntryReg,
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// but the JT now uses PC. Finds the last ADD (if any) that def's EntryReg
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// and is not clobbered / used.
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MachineInstr *RemovableAdd = nullptr;
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unsigned EntryReg = JumpMI->getOperand(0).getReg();
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// Find the last ADD to set EntryReg
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MachineBasicBlock::iterator I(LEAMI);
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for (++I; &*I != JumpMI; ++I) {
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if (I->getOpcode() == ARM::t2ADDrs && I->getOperand(0).getReg() == EntryReg)
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RemovableAdd = &*I;
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}
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if (!RemovableAdd)
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return;
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// Ensure EntryReg is not clobbered or used.
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MachineBasicBlock::iterator J(RemovableAdd);
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for (++J; &*J != JumpMI; ++J) {
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for (unsigned K = 0, E = J->getNumOperands(); K != E; ++K) {
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const MachineOperand &MO = J->getOperand(K);
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if (!MO.isReg() || !MO.getReg())
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continue;
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if (MO.isDef() && MO.getReg() == EntryReg)
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return;
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if (MO.isUse() && MO.getReg() == EntryReg)
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return;
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}
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}
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DEBUG(dbgs() << "Removing Dead Add: " << *RemovableAdd);
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RemovableAdd->eraseFromParent();
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DeadSize += 4;
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}
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static bool registerDefinedBetween(unsigned Reg,
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MachineBasicBlock::iterator From,
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MachineBasicBlock::iterator To,
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@ -2172,7 +2210,10 @@ bool ARMConstantIslands::optimizeThumb2JumpTables() {
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NewJTMI->getOperand(0).setReg(ARM::PC);
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NewJTMI->getOperand(0).setIsKill(false);
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if (CanDeleteLEA) {
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if (CanDeleteLEA) {
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if (isThumb2)
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RemoveDeadAddBetweenLEAAndJT(User.MI, MI, DeadSize);
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User.MI->eraseFromParent();
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DeadSize += isThumb2 ? 4 : 2;
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124
test/CodeGen/Thumb2/tbb-removeadd.mir
Normal file
124
test/CodeGen/Thumb2/tbb-removeadd.mir
Normal file
@ -0,0 +1,124 @@
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#RUN: llc -run-pass arm-cp-islands %s -o - | FileCheck %s
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--- |
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; ModuleID = 'test.ll'
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source_filename = "test.c"
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target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
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target triple = "thumbv8r-arm-none-eabi"
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define void @Func(i32 %i, i32* nocapture %p) local_unnamed_addr {
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entry:
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switch i32 %i, label %sw.epilog [
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i32 0, label %sw.bb
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i32 1, label %sw.bb1
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i32 2, label %sw.epilog.sink.split
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i32 4, label %sw.bb3
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]
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sw.bb: ; preds = %entry
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br label %sw.epilog.sink.split
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sw.bb1: ; preds = %entry
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store i32 0, i32* %p, align 4
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br label %sw.epilog.sink.split
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sw.bb3: ; preds = %entry
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br label %sw.epilog.sink.split
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sw.epilog.sink.split: ; preds = %sw.bb3, %sw.bb1, %sw.bb, %entry
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%.sink = phi i32 [ 2, %sw.bb3 ], [ 0, %sw.bb ], [ 1, %entry ], [ 1, %sw.bb1 ]
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store i32 %.sink, i32* %p, align 4
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br label %sw.epilog
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sw.epilog: ; preds = %sw.epilog.sink.split, %entry
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ret void
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}
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...
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---
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name: Func
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alignment: 1
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exposesReturnsTwice: false
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noVRegs: true
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legalized: false
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regBankSelected: false
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selected: false
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tracksRegLiveness: true
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liveins:
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- { reg: '%r0' }
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- { reg: '%r1' }
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frameInfo:
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isFrameAddressTaken: false
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isReturnAddressTaken: false
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hasStackMap: false
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hasPatchPoint: false
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stackSize: 0
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offsetAdjustment: 0
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maxAlignment: 0
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adjustsStack: false
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hasCalls: false
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maxCallFrameSize: 0
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hasOpaqueSPAdjustment: false
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hasVAStart: false
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hasMustTailInVarArgFunc: false
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jumpTable:
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kind: inline
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entries:
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- id: 0
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blocks: [ '%bb.2.sw.bb', '%bb.3.sw.bb1', '%bb.5.sw.epilog.sink.split',
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'%bb.6.sw.epilog', '%bb.4.sw.bb3' ]
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# The ADD should be deleted along with the LEA
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# CHECK-NOT: t2LEApcrelJT
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# CHECK-NOT: t2ADDrs
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# CHECK: tMOVi8
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# CHECK: t2TBB_JT
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body: |
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bb.0.entry:
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successors: %bb.6.sw.epilog(0x0ccccccb), %bb.1.entry(0x73333335)
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liveins: %r0, %r1
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tCMPi8 %r0, 4, 14, _, implicit-def %cpsr
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t2Bcc %bb.6.sw.epilog, 8, killed %cpsr
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bb.1.entry:
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successors: %bb.2.sw.bb(0x1c71c71c), %bb.3.sw.bb1(0x1c71c71c), %bb.5.sw.epilog.sink.split(0x1c71c71c), %bb.6.sw.epilog(0x0e38e38e), %bb.4.sw.bb3(0x1c71c71c)
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liveins: %r0, %r1
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%r2 = t2LEApcrelJT %jump-table.0, 14, _
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%r3 = t2ADDrs killed %r2, %r0, 18, 14, _, _
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%r2, dead %cpsr = tMOVi8 1, 14, _
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t2BR_JT killed %r3, killed %r0, %jump-table.0
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bb.2.sw.bb:
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successors: %bb.5.sw.epilog.sink.split(0x80000000)
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liveins: %r1
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%r2, dead %cpsr = tMOVi8 0, 14, _
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t2B %bb.5.sw.epilog.sink.split, 14, _
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bb.3.sw.bb1:
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successors: %bb.5.sw.epilog.sink.split(0x80000000)
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liveins: %r1
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%r0, dead %cpsr = tMOVi8 0, 14, _
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%r2, dead %cpsr = tMOVi8 1, 14, _
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tSTRi killed %r0, %r1, 0, 14, _ :: (store 4 into %ir.p)
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t2B %bb.5.sw.epilog.sink.split, 14, _
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bb.4.sw.bb3:
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successors: %bb.5.sw.epilog.sink.split(0x80000000)
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liveins: %r1
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%r2, dead %cpsr = tMOVi8 2, 14, _
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bb.5.sw.epilog.sink.split:
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successors: %bb.6.sw.epilog(0x80000000)
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liveins: %r1, %r2
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tSTRi killed %r2, killed %r1, 0, 14, _ :: (store 4 into %ir.p)
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bb.6.sw.epilog:
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tBX_RET 14, _
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...
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