Check in conditional branches for constant islands. Still need to finish

conditional branches for very large targets. That will be the next small
patch. Everything now should in principle work as good (functionality
wise) as without constant islands so we decided at Mips/Imagination to
make constant islands the default for Mips16 now so that it will get
excercised a lot and this port is still experimentatl though hopefully soon
we will change the status. Some more cleanup and code review is in order
but things are converging fast.

llvm-svn: 195902

2 files changed, 157 insertions, 5 deletions

diff --git a/llvm/lib/Target/Mips/MipsConstantIslandPass.cpp b/llvm/lib/Target/Mips/MipsConstantIslandPass.cpp
index 7ab601c1a1a..3c62baeec15 100644
--- a/llvm/lib/Target/Mips/MipsConstantIslandPass.cpp
+++ b/llvm/lib/Target/Mips/MipsConstantIslandPass.cpp
@@ -77,6 +77,103 @@ static cl::opt<bool> NoLoadRelaxation(
   cl::desc("Don't relax loads to long loads - for testing purposes"),
   cl::Hidden);
 
+static unsigned int branchTargetOperand(MachineInstr *MI) {
+  switch (MI->getOpcode()) {
+  case Mips::Bimm16:
+  case Mips::BimmX16:
+  case Mips::Bteqz16:
+  case Mips::BteqzX16:
+  case Mips::Btnez16:
+  case Mips::BtnezX16:
+  case Mips::Jal16:
+    return 0;
+  case Mips::BeqzRxImm16:
+  case Mips::BeqzRxImmX16:
+  case Mips::BnezRxImm16:
+  case Mips::BnezRxImmX16:
+    return 1;
+  }
+  llvm_unreachable("Unknown branch type");
+}
+
+static unsigned int longformBranchOpcode(unsigned int Opcode) {
+  switch (Opcode) {
+  case Mips::Bimm16:
+  case Mips::BimmX16:
+    return Mips::BimmX16;
+  case Mips::Bteqz16:
+  case Mips::BteqzX16:
+    return Mips::BteqzX16;
+  case Mips::Btnez16:
+  case Mips::BtnezX16:
+    return Mips::BtnezX16;
+  case Mips::Jal16:
+    return Mips::Jal16;
+  case Mips::BeqzRxImm16:
+  case Mips::BeqzRxImmX16:
+    return Mips::BeqzRxImmX16;
+  case Mips::BnezRxImm16:
+  case Mips::BnezRxImmX16:
+    return Mips::BnezRxImmX16;
+  }
+  llvm_unreachable("Unknown branch type");
+}
+
+//
+// FIXME: need to go through this whole constant islands port and check the math
+// for branch ranges and clean this up and make some functions to calculate things
+// that are done many times identically.
+// Need to refactor some of the code to call this routine.
+//
+static unsigned int branchMaxOffsets(unsigned int Opcode) {
+  unsigned Bits, Scale;
+  switch (Opcode) {
+    case Mips::Bimm16:
+      Bits = 11;
+      Scale = 2;
+      break;
+    case Mips::BimmX16:
+      Bits = 16;
+      Scale = 2;
+      break;
+    case Mips::BeqzRxImm16:
+      Bits = 8;
+      Scale = 2;
+      break;
+    case Mips::BeqzRxImmX16:
+      Bits = 16;
+      Scale = 2;
+      break;
+    case Mips::BnezRxImm16:
+      Bits = 8;
+      Scale = 2;
+      break;
+    case Mips::BnezRxImmX16:
+      Bits = 16;
+      Scale = 2;
+      break;
+    case Mips::Bteqz16:
+      Bits = 8;
+      Scale = 2;
+      break;
+    case Mips::BteqzX16:
+      Bits = 16;
+      Scale = 2;
+      break;
+    case Mips::Btnez16:
+      Bits = 8;
+      Scale = 2;
+      break;
+    case Mips::BtnezX16:
+      Bits = 16;
+      Scale = 2;
+      break;
+    default:
+      llvm_unreachable("Unknown branch type");
+  }
+  unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
+  return MaxOffs;
+}
 
 namespace {
 
@@ -603,6 +700,47 @@ initializeFunctionInfo(const std::vector<MachineInstr*> &CPEMIs) {
           Bits = 16;
           Scale = 2;
           isCond = false;
+          break;
+        case Mips::BeqzRxImm16:
+          Bits = 8;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::BeqzRxImmX16:
+          Bits = 16;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::BnezRxImm16:
+          Bits = 8;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::BnezRxImmX16:
+          Bits = 16;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::Bteqz16:
+          Bits = 8;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::BteqzX16:
+          Bits = 16;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::Btnez16:
+          Bits = 8;
+          Scale = 2;
+          isCond = true;
+          break;
+        case Mips::BtnezX16:
+          Bits = 16;
+          Scale = 2;
+          isCond = true;
+          break;
         }
         // Record this immediate branch.
         unsigned MaxOffs = ((1 << (Bits-1))-1) * Scale;
@@ -1382,7 +1520,8 @@ unsigned PCAdj = 4;
 /// away to fit in its displacement field.
 bool MipsConstantIslands::fixupImmediateBr(ImmBranch &Br) {
   MachineInstr *MI = Br.MI;
-  MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
+  unsigned TargetOperand = branchTargetOperand(MI);
+  MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
 
   // Check to see if the DestBB is already in-range.
   if (isBBInRange(MI, DestBB, Br.MaxDisp))
@@ -1434,13 +1573,26 @@ MipsConstantIslands::fixupUnconditionalBr(ImmBranch &Br) {
   return true;
 }
 
+
 /// fixupConditionalBr - Fix up a conditional branch whose destination is too
 /// far away to fit in its displacement field. It is converted to an inverse
 /// conditional branch + an unconditional branch to the destination.
 bool
 MipsConstantIslands::fixupConditionalBr(ImmBranch &Br) {
   MachineInstr *MI = Br.MI;
-  MachineBasicBlock *DestBB = MI->getOperand(0).getMBB();
+  unsigned TargetOperand = branchTargetOperand(MI);
+  MachineBasicBlock *DestBB = MI->getOperand(TargetOperand).getMBB();
+  unsigned Opcode = MI->getOpcode();
+  unsigned LongFormOpcode = longformBranchOpcode(Opcode);
+  unsigned LongFormMaxOff = branchMaxOffsets(LongFormOpcode);
+
+  // Check to see if the DestBB is already in-range.
+  if (isBBInRange(MI, DestBB, LongFormMaxOff)) {
+    Br.MaxDisp = LongFormMaxOff;
+    MI->setDesc(TII->get(LongFormOpcode));
+    return true;
+  }
+  llvm_unreachable("Fixup of very long conditional branch not working yet.");
 
   // Add an unconditional branch to the destination and invert the branch
   // condition to jump over it:
diff --git a/llvm/lib/Target/Mips/MipsSubtarget.cpp b/llvm/lib/Target/Mips/MipsSubtarget.cpp
index 9688f0e264b..5103084db5b 100644
--- a/llvm/lib/Target/Mips/MipsSubtarget.cpp
+++ b/llvm/lib/Target/Mips/MipsSubtarget.cpp
@@ -55,9 +55,9 @@ Mips16HardFloat("mips16-hard-float", cl::NotHidden,
 
 static cl::opt<bool>
 Mips16ConstantIslands(
-  "mips16-constant-islands", cl::Hidden,
-  cl::desc("MIPS: mips16 constant islands enable. experimental feature"),
-  cl::init(false));
+  "mips16-constant-islands", cl::NotHidden,
+  cl::desc("MIPS: mips16 constant islands enable."),
+  cl::init(true));
 
 void MipsSubtarget::anchor() { }