[PowerPC] Fix unwind info with dynamic stack realignment

Summary:
PowerPC DWARF unwind info defined CFA as SP + offset even in a function
where the stack had been dynamically realigned. This clearly doesn't
work because the offset from SP to CFA is not a constant. Fix it by
defining CFA as BP instead.

This was causing the AddressSanitizer null_deref test to fail 50% of
the time, depending on whether SP happened to be 32-byte aligned on
entry to a particular function or not.

Reviewers: willschm, uweigand, hfinkel

Reviewed By: hfinkel

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D6410

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@222996 91177308-0d34-0410-b5e6-96231b3b80d8

test/CodeGen/PowerPC/stack-realign.ll

@@ -37,6 +37,7 @@ entry:
 ; CHECK-DAG: subfic 0, [[REG]], -160
 ; CHECK: stdux 1, 1, 0
 
+; CHECK: .cfi_def_cfa_register r30
 ; CHECK: .cfi_offset r30, -16
 ; CHECK: .cfi_offset lr, 16
 
@@ -59,6 +60,7 @@ entry:
 ; CHECK-FP-DAG: subfic 0, [[REG]], -160
 ; CHECK-FP: stdux 1, 1, 0
 
+; CHECK-FP: .cfi_def_cfa_register r30
 ; CHECK-FP: .cfi_offset r31, -8
 ; CHECK-FP: .cfi_offset r30, -16
 ; CHECK-FP: .cfi_offset lr, 16
@@ -120,6 +122,8 @@ entry:
 ; CHECK-DAG: subfc 0, [[REG3]], [[REG2]]
 ; CHECK: stdux 1, 1, 0
 
+; CHECK: .cfi_def_cfa_register r30
+
 ; CHECK: blr
 
 ; CHECK-32-LABEL: @hoo
@@ -178,6 +182,8 @@ entry:
 ; CHECK-DAG: subfic 0, [[REG]], -192
 ; CHECK: stdux 1, 1, 0
 
+; CHECK: .cfi_def_cfa_register r30
+
 ; CHECK: stfd 30, -16(30)
 
 ; CHECK: blr
@@ -193,6 +199,8 @@ entry:
 ; CHECK-FP-DAG: subfic 0, [[REG]], -192
 ; CHECK-FP: stdux 1, 1, 0
 
+; CHECK-FP: .cfi_def_cfa_register r30
+
 ; CHECK-FP: stfd 30, -16(30)
 
 ; CHECK-FP: blr