From: Christoph Muellner <christoph.muellner@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).
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
Tested with "make check" and no regressions found.
*** gcc/ChangeLog ***
2018-xx-xx Christoph Muellner <christoph.muellner@theobroma-systems.com>
Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
* config/aarch64/aarch64.c (aarch64_uxt_size): Correct the maximum
shift amount for shifted operands.
*** gcc/testsuite/ChangeLog ***
2018-xx-xx Christoph Muellner <christoph.muellner@theobroma-systems.com>
Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
* gcc.target/aarch64/extend.c: Adjust the testcases to cover
the changed shift amount.
---
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