Log 09-19

1 files changed, 10 insertions, 1 deletions

diff --git a/log.md b/log.md
index 239be90..7083d30 100644
--- a/log.md
+++ b/log.md
@@ -24,4 +24,13 @@ Is there an interface to get an auxiliary register in the code generator? For
 example, to swap to registers a third is necessary (or the stack, but then the
 PC and SP cannot be modified). In `w_as_jsr_instruction`, the PC is stored on
 the stack, but PC cannot be `Rd` for `str`. Therefore we need an auxiliary
-register (`8c91384` does this for some cases)
+register (`8c91384` does this for some cases). *Answer on 09-19*.
+
+### 2016-09-19
+Talked to John:
+
+ - (*Answer to question from 09-18*) Registers R14 (LR) and probably also R12
+   are scratch registers and can be used at any time.
+ - When the program counter is stored on the stack in ARM (`str pc,[sp,#-4]!`),
+   the value pushed is actually the PC + 8, which gives space for a call after
+   storing the PC. On Thumb-2 this is different, so this should be checked.