[PowerPC] Extend physical register live range in PPCVSXFMAMutate

If the source of the copy that defines the addend is a physical register, then
its existing live range may not extend to the FMA being mutated. Make sure we
extend the live range of the register to meet the FMA because it will become
its operand in this case.

I don't have an independent test case, but it will be exposed by change to be
committed shortly enabling the use of the machine combiner to do fadd/fmul
reassociation, and will be covered by one of the associated regression tests.

llvm-svn: 242278

diff --git a/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp b/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
index 58d3c3d..9748575 100644 (file)
--- a/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
+++ b/llvm/lib/Target/PowerPC/PPCVSXFMAMutate.cpp
@@ -189,7 +189,6 @@ protected:
 
         // Transform: (O2 * O3) + O1 -> (O2 * O1) + O3.
 
-        unsigned AddReg = AddendMI->getOperand(1).getReg();
         unsigned KilledProdReg = MI->getOperand(KilledProdOp).getReg();
         unsigned OtherProdReg  = MI->getOperand(OtherProdOp).getReg();
 
@@ -220,7 +219,7 @@ protected:
 
         MI->getOperand(0).setReg(KilledProdReg);
         MI->getOperand(1).setReg(KilledProdReg);
-        MI->getOperand(3).setReg(AddReg);
+        MI->getOperand(3).setReg(AddendSrcReg);
         MI->getOperand(2).setReg(OtherProdReg);
 
         MI->getOperand(0).setSubReg(KilledProdSubReg);
@@ -278,6 +277,20 @@ protected:
         }
         DEBUG(dbgs() << "  extended: " << NewFMAInt << '\n');
 
+        // Extend the live interval of the addend source (it might end at the
+        // copy to be removed, or somewhere in between there and here). This
+        // is necessary only if it is a physical register.
+        if (!TargetRegisterInfo::isVirtualRegister(AddendSrcReg))
+          for (MCRegUnitIterator Units(AddendSrcReg, TRI); Units.isValid();
+               ++Units) {
+            unsigned Unit = *Units;
+
+            LiveRange &AddendSrcRange = LIS->getRegUnit(Unit);
+            AddendSrcRange.extendInBlock(LIS->getMBBStartIdx(&MBB),
+                                         FMAIdx.getRegSlot());
+            DEBUG(dbgs() << "  extended: " << AddendSrcRange << '\n');
+          }
+
         FMAInt.removeValNo(FMAValNo);
         DEBUG(dbgs() << "  trimmed:  " << FMAInt << '\n');