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[PR67753] adjust for padding when bypassing memory in assign_parm_setup_block 

Storing a register in memory as a full word and then accessing the
same memory address under a smaller-than-word mode amounts to
right-shifting of the register word on big endian machines.  So, if
BLOCK_REG_PADDING chooses upward padding for BYTES_BIG_ENDIAN, and
we're copying from the entry_parm REG directly to a pseudo, bypassing
any stack slot, perform the shifting explicitly.

This fixes the miscompile of function_return_val_10 in
gcc.target/aarch64/aapcs64/func-ret-4.c for target aarch64_be-elf
introduced in the first patch for 67753.

for  gcc/ChangeLog

	PR rtl-optimization/67753
	PR rtl-optimization/64164
	* function.c (assign_parm_setup_block): Right-shift
	upward-padded big-endian args when bypassing the stack slot.

From-SVN: r230985
This commit is contained in:
Alexandre Oliva 2015-11-26 21:57:40 +00:00 committed by Alexandre Oliva
parent 4d6ca95b9a
commit 1e5d7fd638
2 changed files with 48 additions and 3 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2015-11-26 Alexandre Oliva <aoliva@redhat.com>
PR rtl-optimization/67753
PR rtl-optimization/64164
* function.c (assign_parm_setup_block): Right-shift
upward-padded big-endian args when bypassing the stack slot.
2015-11-26 Maciej W. Rozycki <macro@imgtec.com>
* doc/invoke.texi (Option Summary) <MIPS Options>: Reorder

44
gcc/function.c
View File

@ -3002,6 +3002,38 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
emit_move_insn (change_address (mem, mode, 0), reg);
}
#ifdef BLOCK_REG_PADDING
/* Storing the register in memory as a full word, as
move_block_from_reg below would do, and then using the
MEM in a smaller mode, has the effect of shifting right
if BYTES_BIG_ENDIAN. If we're bypassing memory, the
shifting must be explicit. */
else if (!MEM_P (mem))
{
rtx x;
/* If the assert below fails, we should have taken the
mode != BLKmode path above, unless we have downward
padding of smaller-than-word arguments on a machine
with little-endian bytes, which would likely require
additional changes to work correctly. */
gcc_checking_assert (BYTES_BIG_ENDIAN
&& (BLOCK_REG_PADDING (mode,
data->passed_type, 1)
== upward));
int by = (UNITS_PER_WORD - size) * BITS_PER_UNIT;
x = gen_rtx_REG (word_mode, REGNO (entry_parm));
x = expand_shift (RSHIFT_EXPR, word_mode, x, by,
NULL_RTX, 1);
x = force_reg (word_mode, x);
x = gen_lowpart_SUBREG (GET_MODE (mem), x);
emit_move_insn (mem, x);
}
#endif
/* Blocks smaller than a word on a BYTES_BIG_ENDIAN
machine must be aligned to the left before storing
to memory. Note that the previous test doesn't
@ -3023,14 +3055,20 @@ assign_parm_setup_block (struct assign_parm_data_all *all,
tem = change_address (mem, word_mode, 0);
emit_move_insn (tem, x);
}
else if (!MEM_P (mem))
emit_move_insn (mem, entry_parm);
else
move_block_from_reg (REGNO (entry_parm), mem,
size_stored / UNITS_PER_WORD);
}
else if (!MEM_P (mem))
emit_move_insn (mem, entry_parm);
{
gcc_checking_assert (size > UNITS_PER_WORD);
#ifdef BLOCK_REG_PADDING
gcc_checking_assert (BLOCK_REG_PADDING (GET_MODE (mem),
data->passed_type, 0)
== upward);
#endif
emit_move_insn (mem, entry_parm);
}
else
move_block_from_reg (REGNO (entry_parm), mem,
size_stored / UNITS_PER_WORD);