Mark the PPC CTRRC and CTRRC8 register classes as non-allocatable.

Marking these classes as non-alocatable allows CTR loop generation to
work correctly with the block placement passes, etc. These register
classes are currently used only by some unused TCRETURN patterns.
In future cleanup, these will be removed.

Thanks again to Jakob for suggesting this fix to the CTR loop problem!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158221 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 2 deletions

diff --git a/lib/Target/PowerPC/PPCRegisterInfo.td b/lib/Target/PowerPC/PPCRegisterInfo.td
index 066a8fb469..5ca387629b 100644
--- a/lib/Target/PowerPC/PPCRegisterInfo.td
+++ b/lib/Target/PowerPC/PPCRegisterInfo.td
@@ -316,8 +316,16 @@ def CRBITRC : RegisterClass<"PPC", [i32], 32,
 def CRRC : RegisterClass<"PPC", [i32], 32, (add CR0, CR1, CR5, CR6,
                                                 CR7, CR2, CR3, CR4)>;
 
-def CTRRC : RegisterClass<"PPC", [i32], 32, (add CTR)>;
-def CTRRC8 : RegisterClass<"PPC", [i64], 64, (add CTR8)>;
+// The CTR registers are not allocatable because they're used by the
+// decrement-and-branch instructions, and thus need to stay live across
+// multiple basic blocks.
+def CTRRC : RegisterClass<"PPC", [i32], 32, (add CTR)> {
+  let isAllocatable = 0;
+}
+def CTRRC8 : RegisterClass<"PPC", [i64], 64, (add CTR8)> {
+  let isAllocatable = 0;
+}
+
 def VRSAVERC : RegisterClass<"PPC", [i32], 32, (add VRSAVE)>;
 def CARRYRC : RegisterClass<"PPC", [i32], 32, (add CARRY)> {
   let CopyCost = -1;