maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

Don't insert useful instructions in delay slot of a RETURN. 

llvm-svn: 721
This commit is contained in:
Vikram S. Adve 2001-10-10 20:58:11 +00:00
parent 021d523b2f
commit d50b665acf
2 changed files with 32 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

57
llvm/lib/CodeGen/InstrSched/InstrScheduling.cpp
View File

@ -1258,9 +1258,11 @@ ReplaceNopsWithUsefulInstr(SchedulingManager& S,
// is found for a delay slot, use the NOP that is currently in that slot.
//
// We try to fill the delay slots with useful work for all instructions
// except CALLs. For CALLs, it is nearly always possible to use one of the
// EXCEPT CALLS AND RETURNS.
// For CALLs and RETURNs, it is nearly always possible to use one of the
// call sequence instrs and putting anything else in the delay slot could be
// suboptimal.
// suboptimal. Also, it complicates generating the calling sequence code in
// regalloc.
//
static void
ChooseInstructionsForDelaySlots(SchedulingManager& S,
@ -1271,35 +1273,38 @@ ChooseInstructionsForDelaySlots(SchedulingManager& S,
const TerminatorInst* termInstr = bb->getTerminator();
MachineCodeForVMInstr& termMvec = termInstr->getMachineInstrVec();
vector<SchedGraphNode*> delayNodeVec;
const MachineInstr* brInstr;
const MachineInstr* brInstr = NULL;
assert(termInstr->getOpcode() != Instruction::Call
&& "Call used as terminator?");
// To find instructions that need delay slots without searching the entire
// machine code, we assume the only delayed instructions are CALLs or
// instructions generated for the terminator inst.
// Find the first branch instr in the sequence of machine instrs for term
//
unsigned first = 0;
while (first < termMvec.size() &&
! mii.isBranch(termMvec[first]->getOpCode()))
if (termInstr->getOpcode() != Instruction::Ret)
{
++first;
}
assert(first < termMvec.size() &&
"No branch instructions for BR? Ok, but weird! Delete assertion.");
brInstr = (first < termMvec.size())? termMvec[first] : NULL;
// Compute a vector of the nodes chosen for delay slots and then
// mark delay slots to replace NOPs with these useful instructions.
//
if (brInstr != NULL)
{
SchedGraphNode* brNode = graph->getGraphNodeForInstr(brInstr);
FindUsefulInstructionsForDelaySlots(S, brNode, delayNodeVec);
ReplaceNopsWithUsefulInstr(S, brNode, delayNodeVec, graph);
// To find instructions that need delay slots without searching the full
// machine code, we assume that the only delayed instructions are CALLs
// or instructions generated for the terminator inst.
// Find the first branch instr in the sequence of machine instrs for term
//
unsigned first = 0;
while (first < termMvec.size() &&
! mii.isBranch(termMvec[first]->getOpCode()))
{
++first;
}
assert(first < termMvec.size() &&
"No branch instructions for BR? Ok, but weird! Delete assertion.");
brInstr = (first < termMvec.size())? termMvec[first] : NULL;
// Compute a vector of the nodes chosen for delay slots and then
// mark delay slots to replace NOPs with these useful instructions.
//
if (brInstr != NULL)
{
SchedGraphNode* brNode = graph->getGraphNodeForInstr(brInstr);
FindUsefulInstructionsForDelaySlots(S, brNode, delayNodeVec);
ReplaceNopsWithUsefulInstr(S, brNode, delayNodeVec, graph);
}
}
// Also mark delay slots for other delayed instructions to hold NOPs.

2
llvm/lib/CodeGen/InstrSched/SchedGraph.cpp
View File

@ -632,7 +632,7 @@ SchedGraph::addEdgesForInstruction(const MachineInstr& minstr,
// machine instruction in the instruction sequence for this VM instr
// (at least for now, there is never more than one machine instr).
//
const vector<const Value*>& implicitUses =
const vector<Value*>& implicitUses =
instr.getMachineInstrVec().getImplicitUses();
for (unsigned i=0; i < implicitUses.size(); ++i)
addSSAEdge(node, implicitUses[i], target);