On 05/22/14 16:07, H.J. Lu wrote:
On Thu, May 22, 2014 at 2:33 PM, Kai Tietz <kti...@redhat.com> wrote:
Hello,
This patch avoids for sibling-tail-calls the use of pseudo-register. Instead
it uses for load of memory-address the accumulator-register. By this we avoid
that IRA/LRA need to choose a register. So we reduce register-pressure.
The accumulator-register is always a valid register on tail-call case. All
other registers might be callee-saved, or used for argument-passing. The only
case where we would use the accumulator on call is the variadic-case for x86_64
ABI. Just that this function never is a candidate for sibling-tail-calls.
ChangeLog
2014-05-22 Kai Tietz <kti...@redhat.com>
* config/i386/i386.c (ix86_expand_call): Enforce for sibcalls
on memory the use of accumulator-register.
Regression tested for x86_64-unknown-linux-gnu, x86_64-w64-mingw32, and
i686-pc-cygwin.
Ok for apply?
Regards,
Kai
Index: i386.c
===================================================================
--- i386.c (Revision 210412)
+++ i386.c (Arbeitskopie)
@@ -24898,8 +24898,19 @@ ix86_expand_call (rtx retval, rtx fnaddr, rtx call
? !sibcall_insn_operand (XEXP (fnaddr, 0), word_mode)
: !call_insn_operand (XEXP (fnaddr, 0), word_mode))
{
+ rtx r;
fnaddr = convert_to_mode (word_mode, XEXP (fnaddr, 0), 1);
- fnaddr = gen_rtx_MEM (QImode, copy_to_mode_reg (word_mode, fnaddr));
+ if (!sibcall)
+ r = copy_to_mode_reg (word_mode, fnaddr);
+ else
+ {
+ r = gen_rtx_REG (word_mode, AX_REG)
If fnaddr points to a function with variable argument list in
64-bit, AX_REG may be used to store number of FP arguments
passed in registers.
Right, but as Kai mentioned earlier, a varardic function should have
been rejected by now as a sibcall target.
Regardless, I think adding a check here shouldn't hurt and makes the
backend more bullet-proof if the target independent bits get smarter in
the future.
jeff
