[PowerPC, test] Fix use of undef FileCheck var

LLVM test CodeGen/PowerPC/ctrloops-softfloat.ll tries to check for the
absence of sequences of instructions with several CHECK-NOT with one of
those directives using a variable defined in another. However CHECK-NOT
are checked independently so that is using a variable defined in a
pattern that should not occur in the input.

This commit changes occurence of the variable for the regex used in its
definition, thereby making each CHECK-NOT independent.

Reviewed By: nemanjai

Differential Revision: https://reviews.llvm.org/D99881

Author: Thomas Preud'homme

llvm/test/CodeGen/PowerPC/ctrloops-softfloat.ll

@@ -52,8 +52,8 @@ define void @foo1() #0 {
   br i1 %exitcond, label %1, label %2
   ; CHECK: bl __adddf3
   ; CHECK: cmplwi
-  ; CHECK-NOT: li [[REG1:[0-9]+]], 175
-  ; CHECK-NOT: mtctr [[REG1]]
+  ; CHECK-NOT: li {{[0-9]+}}, 175
+  ; CHECK-NOT: mtctr {{[0-9]+}}
 }
 
 define void @foo2() #0 {
@@ -75,8 +75,8 @@ define void @foo2() #0 {
   br i1 %exitcond, label %1, label %2
   ; CHECK: bl __subdf3
   ; CHECK: cmplwi
-  ; CHECK-NOT: li [[REG1:[0-9]+]], 175
-  ; CHECK-NOT: mtctr [[REG1]]
+  ; CHECK-NOT: li {{[0-9]+}}, 175
+  ; CHECK-NOT: mtctr {{[0-9]+}}
 }
 
 define void @foo3() #0 {
@@ -98,8 +98,8 @@ define void @foo3() #0 {
   br i1 %exitcond, label %1, label %2
   ; CHECK: bl __muldf3
   ; CHECK: cmplwi
-  ; CHECK-NOT: li [[REG1:[0-9]+]], 175
-  ; CHECK-NOT: mtctr [[REG1]]
+  ; CHECK-NOT: li {{[0-9]+}}, 175
+  ; CHECK-NOT: mtctr {{[0-9]+}}
 }
 
 define void @foo4() #0 {
@@ -121,8 +121,8 @@ define void @foo4() #0 {
   br i1 %exitcond, label %1, label %2
   ; CHECK: bl __divdf3
   ; CHECK: cmplwi
-  ; CHECK-NOT: li [[REG1:[0-9]+]], 175
-  ; CHECK-NOT: mtctr [[REG1]]
+  ; CHECK-NOT: li {{[0-9]+}}, 175
+  ; CHECK-NOT: mtctr {{[0-9]+}}
 }
 
 attributes #0 = { "use-soft-float"="true" }