Improve logic that decides if its profitable to commute when some of the virtual registers involved have uses/defs chains connecting them to physical register. Fix up the tests that this change improves.

llvm-svn: 221336

1 files changed, 15 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
index 4ed9bf2fff5..428846a3ce2 100644
--- a/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
+++ b/llvm/lib/CodeGen/TwoAddressInstructionPass.cpp
@@ -545,10 +545,21 @@ isProfitableToCommute(unsigned regA, unsigned regB, unsigned regC,
   if (ToRegA) {
     unsigned FromRegB = getMappedReg(regB, SrcRegMap);
     unsigned FromRegC = getMappedReg(regC, SrcRegMap);
-    bool BComp = !FromRegB || regsAreCompatible(FromRegB, ToRegA, TRI);
-    bool CComp = !FromRegC || regsAreCompatible(FromRegC, ToRegA, TRI);
-    if (BComp != CComp)
-      return !BComp && CComp;
+    bool CompB = FromRegB && regsAreCompatible(FromRegB, ToRegA, TRI);
+    bool CompC = FromRegC && regsAreCompatible(FromRegC, ToRegA, TRI);
+
+    // Compute if any of the following are true:
+    // -RegB is not tied to a register and RegC is compatible with RegA.
+    // -RegB is tied to the wrong physical register, but RegC is.
+    // -RegB is tied to the wrong physical register, and RegC isn't tied.
+    if ((!FromRegB && CompC) || (FromRegB && !CompB && (!FromRegC || CompC)))
+      return true;
+    // Don't compute if any of the following are true:
+    // -RegC is not tied to a register and RegB is compatible with RegA.
+    // -RegC is tied to the wrong physical register, but RegB is.
+    // -RegC is tied to the wrong physical register, and RegB isn't tied.
+    if ((!FromRegC && CompB) || (FromRegC && !CompC && (!FromRegB || CompB)))
+      return false;
   }
 
   // If there is a use of regC between its last def (could be livein) and this