[PowerPC] Correct commutable indices for VSX FMA instructions

Although the first two operands are the ones that can be swapped, the tied
input operand is listed before them, so we need to adjust for that.

I have a test case for this, but it goes along with an upcoming commit (so it
will come soon).

llvm-svn: 204748

1 files changed, 15 insertions, 0 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
index 6b5d78b5814..1f98fe62126 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -282,6 +282,21 @@ PPCInstrInfo::commuteInstruction(MachineInstr *MI, bool NewMI) const {
   return MI;
 }
 
+bool PPCInstrInfo::findCommutedOpIndices(MachineInstr *MI, unsigned &SrcOpIdx1,
+                                         unsigned &SrcOpIdx2) const {
+  // For VSX A-Type FMA instructions, it is the first two operands that can be
+  // commuted, however, because the non-encoded tied input operand is listed
+  // first, the operands to swap are actually the second and third.
+
+  int AltOpc = PPC::getAltVSXFMAOpcode(MI->getOpcode());
+  if (AltOpc == -1)
+    return TargetInstrInfo::findCommutedOpIndices(MI, SrcOpIdx1, SrcOpIdx2);
+
+  SrcOpIdx1 = 2;
+  SrcOpIdx2 = 3;
+  return true;
+}
+
 void PPCInstrInfo::insertNoop(MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator MI) const {
   // This function is used for scheduling, and the nop wanted here is the type