Eliminate a 'tst' that immediately follows an 'and'

by morphing the 'and' to its recording form 'andS'.

This is basically a test commit into this area, to
see whether the bots like me. Several generalizations
can be applied and various avenues of code simplification
are open. I'll introduce those as I go.

I am aware of stylistic input from Bill Wendling, about
where put the analysis complexity, but I am positive
that we can move things around easily and will find a
satisfactory solution.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@113839 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMBaseInstrInfo.cpp

@@ -1372,6 +1372,19 @@ AnalyzeCompare(const MachineInstr *MI, unsigned &SrcReg, int &CmpValue) const {
     SrcReg = MI->getOperand(0).getReg();
     CmpValue = MI->getOperand(1).getImm();
     return true;
+  case ARM::TSTri: {
+      if (MI->getParent()->begin() == MachineBasicBlock::const_iterator(MI))
+        return false;
+      const MachineInstr *AND = llvm::prior(MI);
+      if (AND->getOpcode() != ARM::ANDri)
+        return false;
+      if (MI->getOperand(0).getReg() == AND->getOperand(1).getReg() &&
+          MI->getOperand(1).getImm() == AND->getOperand(2).getImm()) {
+        SrcReg = AND->getOperand(0).getReg();
+        CmpValue = 0;
+        return true;
+      }
+    }
   }
 
   return false;
@@ -1421,6 +1434,8 @@ OptimizeCompareInstr(MachineInstr *CmpInstr, unsigned SrcReg, int CmpValue,
   switch (MI->getOpcode()) {
   default: break;
   case ARM::ADDri:
+  case ARM::ANDri:
+  case ARM::t2ANDri:
   case ARM::SUBri:
   case ARM::t2ADDri:
   case ARM::t2SUBri: