JIT: Add new compare-immed-and-branch primative & drop useless clrex

This allows better use of cbz/cbnz on Thumb2 targets.  Also, removed
the clrex from the inline monitor enter code (not necessary).

Change-Id: I3bfa90bcdf34f6ef3e2447c9c6f1b49a98a89e58

2 files changed, 7 insertions, 14 deletions

diff --git a/vm/compiler/codegen/arm/Thumb2/Factory.c b/vm/compiler/codegen/arm/Thumb2/Factory.c
index 2bf294001..5074e425b 100644
--- a/vm/compiler/codegen/arm/Thumb2/Factory.c
+++ b/vm/compiler/codegen/arm/Thumb2/Factory.c
@@ -1088,15 +1088,13 @@ static void loadPair(CompilationUnit *cUnit, int base, int lowReg, int highReg)
     loadBaseDispWide(cUnit, NULL, base, 0, lowReg, highReg, INVALID_SREG);
 }
 
-
 /*
- * Perform a "reg cmp imm" operation and jump to the PCR region if condition
- * satisfies.
+ * Generate a register comparison to an immediate and branch.  Caller
+ * is responsible for setting branch target field.
  */
-static ArmLIR *genRegImmCheck(CompilationUnit *cUnit,
+static ArmLIR *genCmpImmBranch(CompilationUnit *cUnit,
                               ArmConditionCode cond, int reg,
-                              int checkValue, int dOffset,
-                              ArmLIR *pcrLabel)
+                              int checkValue)
 {
     ArmLIR *branch;
     int modImm;
@@ -1118,7 +1116,7 @@ static ArmLIR *genRegImmCheck(CompilationUnit *cUnit,
         }
         branch = newLIR2(cUnit, kThumbBCond, 0, cond);
     }
-    return genCheckCommon(cUnit, dOffset, branch, pcrLabel);
+    return branch;
 }
 
 static ArmLIR *fpRegCopy(CompilationUnit *cUnit, int rDest, int rSrc)
diff --git a/vm/compiler/codegen/arm/Thumb2/Gen.c b/vm/compiler/codegen/arm/Thumb2/Gen.c
index 36323880b..8858bb01e 100644
--- a/vm/compiler/codegen/arm/Thumb2/Gen.c
+++ b/vm/compiler/codegen/arm/Thumb2/Gen.c
@@ -220,11 +220,6 @@ static void genMonitorEnter(CompilationUnit *cUnit, MIR *mir)
     hopTarget->defMask = ENCODE_ALL;
     hopBranch->generic.target = (LIR *)hopTarget;
 
-    // Clear the lock
-    ArmLIR *inst = newLIR0(cUnit, kThumb2Clrex);
-    // ...and make it a scheduling barrier
-    inst->defMask = ENCODE_ALL;
-
     // Export PC (part 1)
     loadConstant(cUnit, r3, (int) (cUnit->method->insns + mir->offset));
 
@@ -290,8 +285,8 @@ static void genMonitorExit(CompilationUnit *cUnit, MIR *mir)
             sizeof(StackSaveArea) -
             offsetof(StackSaveArea, xtra.currentPc));
     opReg(cUnit, kOpBlx, r7);
-    opRegImm(cUnit, kOpCmp, r0, 0); /* Did we throw? */
-    ArmLIR *branchOver = opCondBranch(cUnit, kArmCondNe);
+    /* Did we throw? */
+    ArmLIR *branchOver = genCmpImmBranch(cUnit, kArmCondNe, r0, 0);
     loadConstant(cUnit, r0,
                  (int) (cUnit->method->insns + mir->offset +
                  dexGetInstrWidthAbs(gDvm.instrWidth, OP_MONITOR_EXIT)));