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authorJakob Stoklund Olesen <stoklund@2pi.dk>2012-01-24 23:28:42 +0000
committerJakob Stoklund Olesen <stoklund@2pi.dk>2012-01-24 23:28:42 +0000
commitd36f5af224594719a10d8b190daf4b56cdb7377f (patch)
tree38419ea63d70da10be2fd74ca7ab8c4a13ebe2e6 /lib/CodeGen
parent1ce6a36610f06a1fb4047ddde1e9bc2f071c0bfb (diff)
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Set correct <def,undef> flags when lowering REG_SEQUENCE.
A REG_SEQUENCE instruction is lowered into a sequence of partial defs: %vreg7:ssub_0<def,undef> = COPY %vreg20:ssub_0 %vreg7:ssub_1<def> = COPY %vreg2 %vreg7:ssub_2<def> = COPY %vreg2 %vreg7:ssub_3<def> = COPY %vreg2 The first def needs an <undef> flag to indicate it is the beginning of the live range, while the other defs are read-modify-write. Previously, we depended on LiveIntervalAnalysis to notice and fix the missing <def,undef>, but that solution was never robust, it was causing problems with ProcessImplicitDefs and the lowering of chained REG_SEQUENCE instructions. This fixes PR11841. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148879 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/CodeGen')
-rw-r--r--lib/CodeGen/TwoAddressInstructionPass.cpp46
1 files changed, 46 insertions, 0 deletions
diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index 8002ff2..63172f4 100644
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -1646,6 +1646,36 @@ static void UpdateRegSequenceSrcs(unsigned SrcReg,
}
}
+// Find the first def of Reg, assuming they are all in the same basic block.
+static MachineInstr *findFirstDef(unsigned Reg, MachineRegisterInfo *MRI) {
+ SmallPtrSet<MachineInstr*, 8> Defs;
+ MachineInstr *First = 0;
+ for (MachineRegisterInfo::def_iterator RI = MRI->def_begin(Reg);
+ MachineInstr *MI = RI.skipInstruction(); Defs.insert(MI))
+ First = MI;
+ if (!First)
+ return 0;
+
+ MachineBasicBlock *MBB = First->getParent();
+ MachineBasicBlock::iterator A = First, B = First;
+ bool Moving;
+ do {
+ Moving = false;
+ if (A != MBB->begin()) {
+ Moving = true;
+ --A;
+ if (Defs.erase(A)) First = A;
+ }
+ if (B != MBB->end()) {
+ Defs.erase(B);
+ ++B;
+ Moving = true;
+ }
+ } while (Moving && !Defs.empty());
+ assert(Defs.empty() && "Instructions outside basic block!");
+ return First;
+}
+
/// CoalesceExtSubRegs - If a number of sources of the REG_SEQUENCE are
/// EXTRACT_SUBREG from the same register and to the same virtual register
/// with different sub-register indices, attempt to combine the
@@ -1874,6 +1904,22 @@ bool TwoAddressInstructionPass::EliminateRegSequences() {
UpdateRegSequenceSrcs(SrcReg, DstReg, SubIdx, MRI, *TRI);
}
+ // Set <def,undef> flags on the first DstReg def in the basic block.
+ // It marks the beginning of the live range. All the other defs are
+ // read-modify-write.
+ if (MachineInstr *Def = findFirstDef(DstReg, MRI)) {
+ for (unsigned i = 0, e = Def->getNumOperands(); i != e; ++i) {
+ MachineOperand &MO = Def->getOperand(i);
+ if (MO.isReg() && MO.isDef() && MO.getReg() == DstReg)
+ MO.setIsUndef();
+ }
+ // Make sure there is a full non-subreg imp-def operand on the
+ // instruction. This shouldn't be necessary, but it seems that at least
+ // RAFast requires it.
+ Def->addRegisterDefined(DstReg, TRI);
+ DEBUG(dbgs() << "First def: " << *Def);
+ }
+
if (IsImpDef) {
DEBUG(dbgs() << "Turned: " << *MI << " into an IMPLICIT_DEF");
MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));