MachineRegisterInfo: Introduce isPhysRegUsed()

This method checks whether a physical regiser or any of its aliases are
used in the function.

Using this function in SIRegisterInfo::findUnusedReg() should also fix
this reported failure:

http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150803/292143.html
http://reviews.llvm.org/rL242173#inline-533

The report doesn't come with a testcase and I don't know enough about
AMDGPU to create one myself.

llvm-svn: 245329

2 files changed, 18 insertions, 7 deletions

diff --git a/llvm/lib/CodeGen/ExecutionDepsFix.cpp b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
index cbc3b80a6a5..c77f0f0c47c 100644
--- a/llvm/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
@@ -733,13 +733,12 @@ bool ExeDepsFix::runOnMachineFunction(MachineFunction &mf) {
   // completely.
   bool anyregs = false;
   const MachineRegisterInfo &MRI = mf.getRegInfo();
-  for (TargetRegisterClass::const_iterator I = RC->begin(), E = RC->end();
-       I != E && !anyregs; ++I)
-    for (MCRegAliasIterator AI(*I, TRI, true); AI.isValid(); ++AI)
-      if (!MRI.reg_nodbg_empty(*AI)) {
-        anyregs = true;
-        break;
-      }
+  for (unsigned Reg : *RC) {
+    if (MRI.isPhysRegUsed(Reg)) {
+      anyregs = true;
+      break;
+    }
+  }
   if (!anyregs) return false;
 
   // Initialize the AliasMap on the first use.
diff --git a/llvm/lib/CodeGen/MachineRegisterInfo.cpp b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
index d3704efb631..574eefe67dd 100644
--- a/llvm/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
@@ -489,3 +489,15 @@ bool MachineRegisterInfo::isPhysRegModified(unsigned PhysReg) const {
   }
   return false;
 }
+
+bool MachineRegisterInfo::isPhysRegUsed(unsigned PhysReg) const {
+  if (UsedPhysRegMask.test(PhysReg))
+    return true;
+  const TargetRegisterInfo *TRI = getTargetRegisterInfo();
+  for (MCRegAliasIterator AliasReg(PhysReg, TRI, true); AliasReg.isValid();
+       ++AliasReg) {
+    if (!reg_nodbg_empty(*AliasReg))
+      return true;
+  }
+  return false;
+}