Hi Christoph,
On 07/11/18 21:51, christoph.muell...@theobroma-systems.com wrote:
From: Christoph Muellner <christoph.muell...@theobroma-systems.com>
The aarch64 ISA specification allows a left shift amount to be applied
after extension in the range of 0 to 4 (encoded in the imm3 field).
Indeed. That looks correct from my reading of the spec as well (section C6.2.3
for example).
This is true for at least the following instructions:
* ADD (extend register)
* ADDS (extended register)
* SUB (extended register)
The result of this patch can be seen, when compiling the following code:
uint64_t myadd(uint64_t a, uint64_t b)
{
return a+(((uint8_t)b)<<4);
}
Without the patch the following sequence will be generated:
0000000000000000 <myadd>:
0: d37c1c21 ubfiz x1, x1, #4, #8
4: 8b000020 add x0, x1, x0
8: d65f03c0 ret
With the patch the ubfiz will be merged into the add instruction:
0000000000000000 <myadd>:
0: 8b211000 add x0, x0, w1, uxtb #4
4: d65f03c0 ret
*** gcc/ChangeLog ***
The patch looks correct to me but can you please clarify how it has been tested?
Patches need to be bootstrapped and the full testsuite run.
I also have a few comments on the ChangeLog
2018-xx-xx Christoph Muellner <christoph.muell...@theobroma-system.com>
Two spaces between your name and the email (also, missing an 's' in the email?).
* gcc/config/aarch64/aarch64.c: Correct the maximum shift amount
for shifted operands.
The path should be relative to the ChangeLog location.
Also, please specify the function name being changed.
In this case it should be
* config/aarch64/aarch64.c (aarch64_uxt_size): Correct...
* gcc/testsuite/gcc.target/aarch64/extend.c: Adjust the
testcases to cover the changed shift amount.
This should be in a separate ChangeLog entry as it will go into
gcc/testsuite/ChangeLog.
The path would be:
* gcc.target/aarch64/extend.c
Signed-off-by: Christoph Muellner <christoph.muell...@theobroma-systems.com>
Signed-off-by: Philipp Tomsich <philipp.toms...@theobroma-systems.com>
GCC doesn't use Signed-off-by tags (though no one will complain about them
either) but if
Philipp Tomsich wrote any of the code here (which I think is implied by the
Signed-off-by tag?) then
his name should appear in the ChangeLog entry.
Thanks for the patch!
As I said, the code looks good to me, but you'll need a maintainer to approve it
(I've cc'ed the aarch64 maintainers for you) once the testing is clarified and
the ChangeLog is fixed.
Kyrill
---
gcc/config/aarch64/aarch64.c | 2 +-
gcc/testsuite/gcc.target/aarch64/extend.c | 16 ++++++++--------
2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index c82c7b6..c85988a 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -8190,7 +8190,7 @@ aarch64_output_casesi (rtx *operands)
int
aarch64_uxt_size (int shift, HOST_WIDE_INT mask)
{
- if (shift >= 0 && shift <= 3)
+ if (shift >= 0 && shift <= 4)
{
int size;
for (size = 8; size <= 32; size *= 2)
diff --git a/gcc/testsuite/gcc.target/aarch64/extend.c
b/gcc/testsuite/gcc.target/aarch64/extend.c
index f399e55..7986c5b 100644
--- a/gcc/testsuite/gcc.target/aarch64/extend.c
+++ b/gcc/testsuite/gcc.target/aarch64/extend.c
@@ -32,8 +32,8 @@ ldr_sxtw0 (char *arr, int i)
unsigned long long
adddi_uxtw (unsigned long long a, unsigned int i)
{
- /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*uxtw #?3" } } */
- return a + ((unsigned long long)i << 3);
+ /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*uxtw #?4" } } */
+ return a + ((unsigned long long)i << 4);
}
unsigned long long
@@ -46,8 +46,8 @@ adddi_uxtw0 (unsigned long long a, unsigned int i)
long long
adddi_sxtw (long long a, int i)
{
- /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*sxtw #?3" } } */
- return a + ((long long)i << 3);
+ /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*sxtw #?4" } } */
+ return a + ((long long)i << 4);
}
long long
@@ -60,8 +60,8 @@ adddi_sxtw0 (long long a, int i)
unsigned long long
subdi_uxtw (unsigned long long a, unsigned int i)
{
- /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*uxtw #?3" } } */
- return a - ((unsigned long long)i << 3);
+ /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*uxtw #?4" } } */
+ return a - ((unsigned long long)i << 4);
}
unsigned long long
@@ -74,8 +74,8 @@ subdi_uxtw0 (unsigned long long a, unsigned int i)
long long
subdi_sxtw (long long a, int i)
{
- /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*sxtw #?3" } } */
- return a - ((long long)i << 3);
+ /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*sxtw #?4" } } */
+ return a - ((long long)i << 4);
}
long long
--
2.9.5
