[mips] Improve robustness of some tests.

Summary:
This is done by removing some hardcoded registers like $at or expecting a single digit register to be selected.

Contains work done by Matheus Almeida.

Reviewers: matheusalmeida, dsanders

Reviewed By: dsanders

Subscribers: tomatabacu

Differential Revision: http://reviews.llvm.org/D4227

llvm-svn: 215640
diff --git a/llvm/test/CodeGen/Mips/cconv/arguments.ll b/llvm/test/CodeGen/Mips/cconv/arguments.ll
index 8fe29f3..1ccc39f 100644
--- a/llvm/test/CodeGen/Mips/cconv/arguments.ll
+++ b/llvm/test/CodeGen/Mips/cconv/arguments.ll
@@ -53,7 +53,7 @@
 ; We won't test the way the global address is calculated in this test. This is
 ; just to get the register number for the other checks.
 ; SYM32-DAG:           addiu [[R1:\$[0-9]+]], ${{[0-9]+}}, %lo(bytes)
-; SYM64-DAG:           ld [[R1:\$[0-9]]], %got_disp(bytes)(
+; SYM64-DAG:           ld [[R1:\$[0-9]+]], %got_disp(bytes)(
 
 ; The first four arguments are the same in O32/N32/N64
 ; ALL-DAG:           sb $4, 1([[R1]])
@@ -117,9 +117,9 @@
 ; We won't test the way the global address is calculated in this test. This is
 ; just to get the register number for the other checks.
 ; SYM32-DAG:           addiu [[R1:\$[0-9]+]], ${{[0-9]+}}, %lo(bytes)
-; SYM64-DAG:           ld [[R1:\$[0-9]]], %got_disp(bytes)(
+; SYM64-DAG:           ld [[R1:\$[0-9]+]], %got_disp(bytes)(
 ; SYM32-DAG:           addiu [[R2:\$[0-9]+]], ${{[0-9]+}}, %lo(dwords)
-; SYM64-DAG:           ld [[R2:\$[0-9]]], %got_disp(dwords)(
+; SYM64-DAG:           ld [[R2:\$[0-9]+]], %got_disp(dwords)(
 
 ; The first argument is the same in O32/N32/N64.
 ; ALL-DAG:           sb $4, 1([[R1]])