[Hexagon] Allow setting register in BitVal without storing into map

In the bit tracker, references to other bit values in which the register
is 0 are prohibited. This means that generating self-referential register
cells like { w:32 [0-15]:s[0-15] [16-31]:s[15] } is impossible. In order
to get a self-referential cell, it had to be stored into a map and then
reloaded from it. To avoid this step, add a function that will set the
register to a given value without going through the map.

llvm-svn: 296025

2 files changed, 13 insertions, 6 deletions

diff --git a/llvm/lib/Target/Hexagon/BitTracker.cpp b/llvm/lib/Target/Hexagon/BitTracker.cpp
index 963fb99ce09..61d3630ac09 100644
--- a/llvm/lib/Target/Hexagon/BitTracker.cpp
+++ b/llvm/lib/Target/Hexagon/BitTracker.cpp
@@ -317,6 +317,15 @@ bool BT::RegisterCell::operator== (const RegisterCell &RC) const {
   return true;
 }
 
+BT::RegisterCell &BT::RegisterCell::regify(unsigned R) {
+  for (unsigned i = 0, n = width(); i < n; ++i) {
+    const BitValue &V = Bits[i];
+    if (V.Type == BitValue::Ref && V.RefI.Reg == 0)
+      Bits[i].RefI = BitRef(R, i);
+  }
+  return *this;
+}
+
 uint16_t BT::MachineEvaluator::getRegBitWidth(const RegisterRef &RR) const {
   // The general problem is with finding a register class that corresponds
   // to a given reference reg:sub. There can be several such classes, and
@@ -378,12 +387,7 @@ void BT::MachineEvaluator::putCell(const RegisterRef &RR, RegisterCell RC,
     return;
   assert(RR.Sub == 0 && "Unexpected sub-register in definition");
   // Eliminate all ref-to-reg-0 bit values: replace them with "self".
-  for (unsigned i = 0, n = RC.width(); i < n; ++i) {
-    const BitValue &V = RC[i];
-    if (V.Type == BitValue::Ref && V.RefI.Reg == 0)
-      RC[i].RefI = BitRef(RR.Reg, i);
-  }
-  M[RR.Reg] = RC;
+  M[RR.Reg] = RC.regify(RR.Reg);
 }
 
 // Check if the cell represents a compile-time integer value.
diff --git a/llvm/lib/Target/Hexagon/BitTracker.h b/llvm/lib/Target/Hexagon/BitTracker.h
index 48c5f2266ac..a547b34e852 100644
--- a/llvm/lib/Target/Hexagon/BitTracker.h
+++ b/llvm/lib/Target/Hexagon/BitTracker.h
@@ -283,6 +283,9 @@ struct BitTracker::RegisterCell {
     return !operator==(RC);
   }
 
+  // Replace the ref-to-reg-0 bit values with the given register.
+  RegisterCell &regify(unsigned R);
+
   // Generate a "ref" cell for the corresponding register. In the resulting
   // cell each bit will be described as being the same as the corresponding
   // bit in register Reg (i.e. the cell is "defined" by register Reg).