Hello!
Symbol references are not legitimate sibcall operands for
-mcmodel=large, so have to be moved to registers (using movabs).
Unfortunately, moving symbol references for CM_LARGE_PIC requires PIC
fixup which by default generates Pmode pseudos. When generating thunk
in x86_output_mi_thunk, we are already past reload time, so pseudos
are not allowed.
The solution is to call legitimize_pic_address with hard temporary
Pmode register in advance, to avoid situations that would lead to
generation of pseudo registers in emit_move_insn. Patched gcc
generates:
.set .LTHUNK0,_ZN1D4foo2Ev
.p2align 4,,15
.globl _ZThn16_N1D4foo2Ev
.type _ZThn16_N1D4foo2Ev, @function
_ZThn16_N1D4foo2Ev:
.LFB15:
.cfi_startproc
subq $16, %rdi
movabsq $.LTHUNK0@GOTOFF, %r10
addq %rbx, %r10
jmp *%r10
.cfi_endproc
.LFE15:
.size _ZThn16_N1D4foo2Ev, .-_ZThn16_N1D4foo2Ev
which is the same as when calling static local functions with
-mcmodel=large -fPIC.
2012-07-06 Uros Bizjak <ubiz...@gmail.com>
PR target/53811
* config/i386/i386.c (x86_output_mi_thunk): For CM_LARGE_PIC model,
emit PIC sequence for fnaddr symbol reference in advance.
Tested on x86_64-pc-linux-gnu {,-m32} and by testing various runtime
tests in testsuite/g++.dg/inherit with "-mcmodel=large -fPIC".
Committed to mainline SVN, will backport to 4.7.
Uros.
Index: config/i386/i386.c
===================================================================
--- config/i386/i386.c (revision 189310)
+++ config/i386/i386.c (working copy)
@@ -33057,6 +33057,10 @@ x86_output_mi_thunk (FILE *file,
emit_jump_insn (gen_indirect_jump (fnaddr));
else
{
+ if (ix86_cmodel == CM_LARGE_PIC && SYMBOLIC_CONST (fnaddr))
+ fnaddr = legitimize_pic_address (fnaddr,
+ gen_rtx_REG (Pmode, tmp_regno));
+
if (!sibcall_insn_operand (fnaddr, word_mode))
{
tmp = gen_rtx_REG (word_mode, tmp_regno);
