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-rw-r--r--target-s390x/cpu.h7
1 files changed, 7 insertions, 0 deletions
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index 4fb34b598d..4e58cdee3e 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -671,6 +671,13 @@ ObjectClass *s390_cpu_class_by_name(const char *name);
/* CC optimization */
+/* Instead of computing the condition codes after each x86 instruction,
+ * QEMU just stores the result (called CC_DST), the type of operation
+ * (called CC_OP) and whatever operands are needed (CC_SRC and possibly
+ * CC_VR). When the condition codes are needed, the condition codes can
+ * be calculated using this information. Condition codes are not generated
+ * if they are only needed for conditional branches.
+ */
enum cc_op {
CC_OP_CONST0 = 0, /* CC is 0 */
CC_OP_CONST1, /* CC is 1 */