[PATCH] D42392: [AArch64] Add new target feature to fuse conditional select

[Evandro Menezes via Phabricator via llvm-commits]

evandro updated this revision to Diff 135539.
evandro added a comment.

Updated patch considering the refactoring in https://reviews.llvm.org/D43649.


https://reviews.llvm.org/D42392

Files:
  llvm/lib/Target/AArch64/AArch64MacroFusion.cpp


Index: llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
===================================================================
--- llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
+++ llvm/lib/Target/AArch64/AArch64MacroFusion.cpp
@@ -213,6 +213,57 @@
   return false;
 }
 
+// Fuse compare and conditional select.
+static bool isCCSelectPair(const MachineInstr *FirstMI,
+                           const MachineInstr &SecondMI) {
+  unsigned SecondOpcode = SecondMI.getOpcode();
+
+  // 32 bits
+  if (SecondOpcode == AArch64::CSELWr) {
+    // Assume the 1st instr to be a wildcard if it is unspecified.
+    if (!FirstMI)
+      return true;
+
+    if (FirstMI->definesRegister(AArch64::WZR))
+      switch (FirstMI->getOpcode()) {
+      case AArch64::SUBSWrs:
+        if (AArch64InstrInfo::hasShiftedReg(*FirstMI))
+          return false;
+        return true;
+      case AArch64::SUBSWrx:
+        if (AArch64InstrInfo::hasExtendedReg(*FirstMI))
+          return false;
+        return true;
+      case AArch64::SUBSWrr:
+      case AArch64::SUBSWri:
+        return true;
+      }
+  }
+  // 64 bits
+  else if (SecondOpcode == AArch64::CSELXr) {
+    // Assume the 1st instr to be a wildcard if it is unspecified.
+    if (!FirstMI)
+      return true;
+
+    if (FirstMI->definesRegister(AArch64::XZR))
+      switch (FirstMI->getOpcode()) {
+      case AArch64::SUBSXrs:
+        if (AArch64InstrInfo::hasShiftedReg(*FirstMI))
+          return false;
+        return true;
+      case AArch64::SUBSXrx:
+      case AArch64::SUBSXrx64:
+        if (AArch64InstrInfo::hasExtendedReg(*FirstMI))
+          return false;
+        return true;
+      case AArch64::SUBSXrr:
+      case AArch64::SUBSXri:
+        return true;
+      }
+  }
+  return false;
+}
+
 /// \brief Check if the instr pair, FirstMI and SecondMI, should be fused
 /// together. Given SecondMI, when FirstMI is unspecified, then check if
 /// SecondMI may be part of a fused pair at all.
@@ -232,6 +283,8 @@
     return true;
   if (ST.hasFuseAddress() && isAddressLdStPair(FirstMI, SecondMI))
     return true;
+  if (ST.hasFuseCCSelect() && isCCSelectPair(FirstMI, SecondMI))
+    return true;
 
   return false;
 }


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