Revert r351938 "[ARM] Alter the register allocation order for minsize on Thumb2"

This change caused fatal backend errors when compiling a file in libvpx
for Android.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@351979 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rnk

lib/Target/ARM/ARMRegisterInfo.td

@@ -204,21 +204,13 @@ def FPINST2 : ARMReg<10, "fpinst2">;
 def GPR : RegisterClass<"ARM", [i32], 32, (add (sequence "R%u", 0, 12),
                                                SP, LR, PC)> {
   // Allocate LR as the first CSR since it is always saved anyway.
-  // For Thumb2, using LR would force 32bit Thumb2 instructions, not the smaller
-  // Thumb1 ones. It is a little better for codesize on average to use the
-  // default order.
   // For Thumb1 mode, we don't want to allocate hi regs at all, as we don't
   // know how to spill them. If we make our prologue/epilogue code smarter at
   // some point, we can go back to using the above allocation orders for the
   // Thumb1 instructions that know how to use hi regs.
   let AltOrders = [(add LR, GPR), (trunc GPR, 8)];
   let AltOrderSelect = [{
-      if (MF.getSubtarget<ARMSubtarget>().isThumb1Only())
-        return 2;
-      if (MF.getSubtarget<ARMSubtarget>().isThumb2() &&
-          MF.getFunction().optForMinSize())
-        return 0;
-      return 1;
+      return 1 + MF.getSubtarget<ARMSubtarget>().isThumb1Only();
   }];
   let DiagnosticString = "operand must be a register in range [r0, r15]";
 }
@@ -229,12 +221,7 @@ def GPR : RegisterClass<"ARM", [i32], 32, (add (sequence "R%u", 0, 12),
 def GPRnopc : RegisterClass<"ARM", [i32], 32, (sub GPR, PC)> {
   let AltOrders = [(add LR, GPRnopc), (trunc GPRnopc, 8)];
   let AltOrderSelect = [{
-      if (MF.getSubtarget<ARMSubtarget>().isThumb1Only())
-        return 2;
-      if (MF.getSubtarget<ARMSubtarget>().isThumb2() &&
-          MF.getFunction().optForMinSize())
-        return 0;
-      return 1;
+      return 1 + MF.getSubtarget<ARMSubtarget>().isThumb1Only();
   }];
   let DiagnosticString = "operand must be a register in range [r0, r14]";
 }
@@ -245,12 +232,7 @@ def GPRnopc : RegisterClass<"ARM", [i32], 32, (sub GPR, PC)> {
 def GPRwithAPSR : RegisterClass<"ARM", [i32], 32, (add (sub GPR, PC), APSR_NZCV)> {
   let AltOrders = [(add LR, GPRnopc), (trunc GPRnopc, 8)];
   let AltOrderSelect = [{
-      if (MF.getSubtarget<ARMSubtarget>().isThumb1Only())
-        return 2;
-      if (MF.getSubtarget<ARMSubtarget>().isThumb2() &&
-          MF.getFunction().optForMinSize())
-        return 0;
-      return 1;
+      return 1 + MF.getSubtarget<ARMSubtarget>().isThumb1Only();
   }];
   let DiagnosticString = "operand must be a register in range [r0, r14] or apsr_nzcv";
 }
@@ -271,12 +253,7 @@ def GPRsp : RegisterClass<"ARM", [i32], 32, (add SP)> {
 def rGPR : RegisterClass<"ARM", [i32], 32, (sub GPR, SP, PC)> {
   let AltOrders = [(add LR, rGPR), (trunc rGPR, 8)];
   let AltOrderSelect = [{
-      if (MF.getSubtarget<ARMSubtarget>().isThumb1Only())
-        return 2;
-      if (MF.getSubtarget<ARMSubtarget>().isThumb2() &&
-          MF.getFunction().optForMinSize())
-        return 0;
-      return 1;
+      return 1 + MF.getSubtarget<ARMSubtarget>().isThumb1Only();
   }];
   let DiagnosticType = "rGPR";
 }