On 09/09/2016 09:33 AM, Segher Boessenkool wrote:
On Thu, Sep 08, 2016 at 11:20:41AM -0600, Jeff Law wrote:
On 08/29/2016 03:31 AM, Bernd Schmidt wrote:
On 08/01/2016 03:42 AM, Segher Boessenkool wrote:
+@deftypefn {Target Hook} void
TARGET_SHRINK_WRAP_EMIT_PROLOGUE_COMPONENTS (sbitmap)
+Emit prologue insns for the components indicated by the parameter.
+@end deftypefn
+
+@deftypefn {Target Hook} void
TARGET_SHRINK_WRAP_EMIT_EPILOGUE_COMPONENTS (sbitmap)
+Emit epilogue insns for the components indicated by the parameter.
+@end deftypefn
How do these actually know where to save/restore registers? The frame
pointer may have been eliminated, and SP isn't necessarily constant
during the function. Seems like you'd have to calculate CFA reg/offset
much like dwarf2out does and pass it to this hook.
So I think the confusion here is these hooks are independent of
placement. ie, the target independent code does something like:
FOR_EACH_BB
Build the component bitmap using the incoming edge components
Emit the prologue components at the start of the block
Emit the epilogue components at the end of the block
So you think those hooks need a BB parameter? If there are ports that
need that, then sure. PowerPC doesn't need it.
I wouldn't add it now. If we find a port that needs it, we can do so at
that time. Maybe the port wants to scan the block for a scratch
register or somesuch. But let's wait until we actually see a need.
I was mostly trying to highlight the high level structure and that each
block can have a prologue and/or epilogue associated with it and that
they are specialized for each block.
jeff
