Mathieu Desnoyers wrote:
This epilogue should then be used on both branches of the condition,
like this :
if (unlikely(imv_cond(var))) {
imv_cond_end();
...
} else {
imv_cond_end();
...
}
Where imv_cond_end() would look like this :
+/*
+ * Puts a test and branch make sure the %al register and ZF are not live
+ * anymore.
+ * All asm statements clobbers the flags, but add "cc" clobber just to be sure.
+ * Clobbers %al.
+ */
+#define imv_cond_end() \
+ do { \
+ asm (".section __imv_cond_end,\"a\",@progbits\n\t" \
+ _ASM_PTR "1f\n\t" \
+ ".previous\n\t" \
+ "1:\n\t" \
+ : : : "a", "cc"); \
+ } while (0)
+
As far as this is concerned, all you accomplish here is that gcc, if it
wants to re-use the %al value, will copy it into another register before
doing your imv_conv_end().
-hpa
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