This patch adds routines for converting a SUBREG_BYTE offset into a
memory address offset. The two only differ for paradoxical subregs,
where SUBREG_BYTE is always 0 but the memory address offset can be
negative.
Tested on aarch64-linux-gnu and x86_64-linux-gnu, and by checking
there was no change in the testsuite assembly output for at least
one target per CPU. OK to install?
Richard
2017-08-28 Richard Sandiford <richard.sandif...@linaro.org>
Alan Hayward <alan.hayw...@arm.com>
David Sherwood <david.sherw...@arm.com>
gcc/
* rtl.h (subreg_memory_offset): Declare.
* emit-rtl.c (subreg_memory_offset): New function.
* expmed.c (store_bit_field_1): Use it.
* expr.c (undefined_operand_subword_p): Likewise.
* simplify-rtx.c (simplify_subreg): Likewise.
Index: gcc/rtl.h
===================================================================
--- gcc/rtl.h 2017-08-27 23:19:56.284397205 +0100
+++ gcc/rtl.h 2017-08-28 09:19:13.737714836 +0100
@@ -2827,6 +2827,8 @@ subreg_highpart_offset (machine_mode out
}
extern int byte_lowpart_offset (machine_mode, machine_mode);
+extern int subreg_memory_offset (machine_mode, machine_mode, unsigned int);
+extern int subreg_memory_offset (const_rtx);
extern rtx make_safe_from (rtx, rtx);
extern rtx convert_memory_address_addr_space_1 (machine_mode, rtx,
addr_space_t, bool, bool);
Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c 2017-08-22 17:14:30.335896832 +0100
+++ gcc/emit-rtl.c 2017-08-28 09:19:13.736814836 +0100
@@ -1013,6 +1013,33 @@ byte_lowpart_offset (machine_mode outer_
else
return subreg_lowpart_offset (outer_mode, inner_mode);
}
+
+/* Return the offset of (subreg:OUTER_MODE (mem:INNER_MODE X) OFFSET)
+ from address X. For paradoxical big-endian subregs this is a
+ negative value, otherwise it's the same as OFFSET. */
+
+int
+subreg_memory_offset (machine_mode outer_mode, machine_mode inner_mode,
+ unsigned int offset)
+{
+ if (paradoxical_subreg_p (outer_mode, inner_mode))
+ {
+ gcc_assert (offset == 0);
+ return -subreg_lowpart_offset (inner_mode, outer_mode);
+ }
+ return offset;
+}
+
+/* As above, but return the offset that existing subreg X would have
+ if SUBREG_REG (X) were stored in memory. The only significant thing
+ about the current SUBREG_REG is its mode. */
+
+int
+subreg_memory_offset (const_rtx x)
+{
+ return subreg_memory_offset (GET_MODE (x), GET_MODE (SUBREG_REG (x)),
+ SUBREG_BYTE (x));
+}
/* Generate a REG rtx for a new pseudo register of mode MODE.
This pseudo is assigned the next sequential register number. */
Index: gcc/expmed.c
===================================================================
--- gcc/expmed.c 2017-08-27 23:19:56.284397205 +0100
+++ gcc/expmed.c 2017-08-28 09:19:13.736814836 +0100
@@ -726,29 +726,7 @@ store_bit_field_1 (rtx str_rtx, unsigned
while (GET_CODE (op0) == SUBREG)
{
- /* The following line once was done only if WORDS_BIG_ENDIAN,
- but I think that is a mistake. WORDS_BIG_ENDIAN is
- meaningful at a much higher level; when structures are copied
- between memory and regs, the higher-numbered regs
- always get higher addresses. */
- int inner_mode_size = GET_MODE_SIZE (GET_MODE (SUBREG_REG (op0)));
- int outer_mode_size = GET_MODE_SIZE (GET_MODE (op0));
- int byte_offset = 0;
-
- /* Paradoxical subregs need special handling on big-endian machines. */
- if (paradoxical_subreg_p (op0))
- {
- int difference = inner_mode_size - outer_mode_size;
-
- if (WORDS_BIG_ENDIAN)
- byte_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- byte_offset += difference % UNITS_PER_WORD;
- }
- else
- byte_offset = SUBREG_BYTE (op0);
-
- bitnum += byte_offset * BITS_PER_UNIT;
+ bitnum += subreg_memory_offset (op0) * BITS_PER_UNIT;
op0 = SUBREG_REG (op0);
}
Index: gcc/expr.c
===================================================================
--- gcc/expr.c 2017-08-27 23:19:56.149397206 +0100
+++ gcc/expr.c 2017-08-28 09:19:13.737714836 +0100
@@ -3524,30 +3524,12 @@ emit_move_ccmode (machine_mode mode, rtx
static bool
undefined_operand_subword_p (const_rtx op, int i)
{
- machine_mode innermode, innermostmode;
- int offset;
if (GET_CODE (op) != SUBREG)
return false;
- innermode = GET_MODE (op);
- innermostmode = GET_MODE (SUBREG_REG (op));
- offset = i * UNITS_PER_WORD + SUBREG_BYTE (op);
- /* The SUBREG_BYTE represents offset, as if the value were stored in
- memory, except for a paradoxical subreg where we define
- SUBREG_BYTE to be 0; undo this exception as in
- simplify_subreg. */
- if (SUBREG_BYTE (op) == 0
- && GET_MODE_SIZE (innermostmode) < GET_MODE_SIZE (innermode))
- {
- int difference = (GET_MODE_SIZE (innermostmode) - GET_MODE_SIZE
(innermode));
- if (WORDS_BIG_ENDIAN)
- offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- offset += difference % UNITS_PER_WORD;
- }
- if (offset >= GET_MODE_SIZE (innermostmode)
- || offset <= -GET_MODE_SIZE (word_mode))
- return true;
- return false;
+ machine_mode innermostmode = GET_MODE (SUBREG_REG (op));
+ HOST_WIDE_INT offset = i * UNITS_PER_WORD + subreg_memory_offset (op);
+ return (offset >= GET_MODE_SIZE (innermostmode)
+ || offset <= -UNITS_PER_WORD);
}
/* A subroutine of emit_move_insn_1. Generate a move from Y into X.
Index: gcc/simplify-rtx.c
===================================================================
--- gcc/simplify-rtx.c 2017-08-27 23:19:56.284397205 +0100
+++ gcc/simplify-rtx.c 2017-08-28 09:19:13.739514836 +0100
@@ -6050,34 +6050,18 @@ simplify_subreg (machine_mode outermode,
if (GET_CODE (op) == SUBREG)
{
machine_mode innermostmode = GET_MODE (SUBREG_REG (op));
- int final_offset = byte + SUBREG_BYTE (op);
rtx newx;
if (outermode == innermostmode
&& byte == 0 && SUBREG_BYTE (op) == 0)
return SUBREG_REG (op);
- /* The SUBREG_BYTE represents offset, as if the value were stored
- in memory. Irritating exception is paradoxical subreg, where
- we define SUBREG_BYTE to be 0. On big endian machines, this
- value should be negative. For a moment, undo this exception. */
- if (byte == 0 && GET_MODE_SIZE (innermode) < GET_MODE_SIZE (outermode))
- {
- int difference = (GET_MODE_SIZE (innermode) - GET_MODE_SIZE
(outermode));
- if (WORDS_BIG_ENDIAN)
- final_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- final_offset += difference % UNITS_PER_WORD;
- }
- if (SUBREG_BYTE (op) == 0
- && GET_MODE_SIZE (innermostmode) < GET_MODE_SIZE (innermode))
- {
- int difference = (GET_MODE_SIZE (innermostmode) - GET_MODE_SIZE
(innermode));
- if (WORDS_BIG_ENDIAN)
- final_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- final_offset += difference % UNITS_PER_WORD;
- }
+ /* Work out the memory offset of the final OUTERMODE value relative
+ to the inner value of OP. */
+ HOST_WIDE_INT mem_offset = subreg_memory_offset (outermode,
+ innermode, byte);
+ HOST_WIDE_INT op_mem_offset = subreg_memory_offset (op);
+ HOST_WIDE_INT final_offset = mem_offset + op_mem_offset;
/* See whether resulting subreg will be paradoxical. */
if (!paradoxical_subreg_p (outermode, innermostmode))
@@ -6092,19 +6076,12 @@ simplify_subreg (machine_mode outermode,
}
else
{
- int offset = 0;
- int difference = (GET_MODE_SIZE (innermostmode) - GET_MODE_SIZE
(outermode));
-
- /* In paradoxical subreg, see if we are still looking on lower part.
- If so, our SUBREG_BYTE will be 0. */
- if (WORDS_BIG_ENDIAN)
- offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- offset += difference % UNITS_PER_WORD;
- if (offset == final_offset)
- final_offset = 0;
- else
+ HOST_WIDE_INT required_offset
+ = subreg_memory_offset (outermode, innermostmode, 0);
+ if (final_offset != required_offset)
return NULL_RTX;
+ /* Paradoxical subregs always have byte offset 0. */
+ final_offset = 0;
}
/* Recurse for further possible simplifications. */
@@ -6145,22 +6122,9 @@ simplify_subreg (machine_mode outermode,
final_regno = simplify_subreg_regno (regno, innermode, byte, outermode);
if (HARD_REGISTER_NUM_P (final_regno))
{
- rtx x;
- int final_offset = byte;
-
- /* Adjust offset for paradoxical subregs. */
- if (byte == 0
- && GET_MODE_SIZE (innermode) < GET_MODE_SIZE (outermode))
- {
- int difference = (GET_MODE_SIZE (innermode)
- - GET_MODE_SIZE (outermode));
- if (WORDS_BIG_ENDIAN)
- final_offset += (difference / UNITS_PER_WORD) * UNITS_PER_WORD;
- if (BYTES_BIG_ENDIAN)
- final_offset += difference % UNITS_PER_WORD;
- }
-
- x = gen_rtx_REG_offset (op, outermode, final_regno, final_offset);
+ rtx x = gen_rtx_REG_offset (op, outermode, final_regno,
+ subreg_memory_offset (outermode,
+ innermode, byte));
/* Propagate original regno. We don't have any way to specify
the offset inside original regno, so do so only for lowpart.
