TwoAddrInstructionPass::tryInstructionTransform() has a case where it calls

itself recursively with a new instruction that has not been finalized, in order
to determine whether to keep the instruction. On 'make check' and test-suite the
only cases where the recursive invocation made any transformations were simple
instruction commutations, so I am restricting the recursive invocation to do
only this.

The other cases wouldn't work correctly when updating LiveIntervals, since the
new instructions don't have slot indices and LiveIntervals hasn't yet been
updated. If the other transformations were actually triggering in any test case
it would be possible to support it with a lot of effort, but since they don't
it's not worth it.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175979 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/TwoAddressInstructionPass.cpp b/lib/CodeGen/TwoAddressInstructionPass.cpp
index 2ed6be4f0090e381f1088be85de966634313909c..34946ec1ce9ac89525eadc3f942c00d277a3fb05 100644 (file)
--- a/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -120,7 +120,7 @@ class TwoAddressInstructionPass : public MachineFunctionPass {
   bool tryInstructionTransform(MachineBasicBlock::iterator &mi,
                                MachineBasicBlock::iterator &nmi,
                                unsigned SrcIdx, unsigned DstIdx,
-                               unsigned Dist);
+                               unsigned Dist, bool shouldOnlyCommute);
 
   void scanUses(unsigned DstReg);
 
@@ -1085,11 +1085,13 @@ rescheduleKillAboveMI(MachineBasicBlock::iterator &mi,
 /// either eliminate the tied operands or improve the opportunities for
 /// coalescing away the register copy.  Returns true if no copy needs to be
 /// inserted to untie mi's operands (either because they were untied, or
-/// because mi was rescheduled, and will be visited again later).
+/// because mi was rescheduled, and will be visited again later). If the
+/// shouldOnlyCommute flag is true, only instruction commutation is attempted.
 bool TwoAddressInstructionPass::
 tryInstructionTransform(MachineBasicBlock::iterator &mi,
                         MachineBasicBlock::iterator &nmi,
-                        unsigned SrcIdx, unsigned DstIdx, unsigned Dist) {
+                        unsigned SrcIdx, unsigned DstIdx,
+                        unsigned Dist, bool shouldOnlyCommute) {
   if (OptLevel == CodeGenOpt::None)
     return false;
 
@@ -1138,6 +1140,9 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
     return false;
   }
 
+  if (shouldOnlyCommute)
+    return false;
+
   // If there is one more use of regB later in the same MBB, consider
   // re-schedule this MI below it.
   if (rescheduleMIBelowKill(mi, nmi, regB)) {
@@ -1214,7 +1219,7 @@ tryInstructionTransform(MachineBasicBlock::iterator &mi,
         unsigned NewSrcIdx = NewMIs[1]->findRegisterUseOperandIdx(regB);
         MachineBasicBlock::iterator NewMI = NewMIs[1];
         bool TransformSuccess =
-          tryInstructionTransform(NewMI, mi, NewSrcIdx, NewDstIdx, Dist);
+          tryInstructionTransform(NewMI, mi, NewSrcIdx, NewDstIdx, Dist, true);
         if (TransformSuccess ||
             NewMIs[1]->getOperand(NewSrcIdx).isKill()) {
           // Success, or at least we made an improvement. Keep the unfolded
@@ -1539,7 +1544,7 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &Func) {
           unsigned SrcReg = mi->getOperand(SrcIdx).getReg();
           unsigned DstReg = mi->getOperand(DstIdx).getReg();
           if (SrcReg != DstReg &&
-              tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist)) {
+              tryInstructionTransform(mi, nmi, SrcIdx, DstIdx, Dist, false)) {
             // The tied operands have been eliminated or shifted further down the
             // block to ease elimination. Continue processing with 'nmi'.
             TiedOperands.clear();