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.muell...@theobroma-systems.com>
Philipp Tomsich <philipp.toms...@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.muell...@theobroma-systems.com>
Philipp Tomsich <philipp.toms...@theobroma-systems.com>
* gcc.target/aarch64/extend.c: Adjust the testcases to cover
the changed shift amount.
Signed-off-by: Christoph Muellner <christoph.muell...@theobroma-systems.com>
---
gcc/config/aarch64/aarch64.c | 2 +-
gcc/testsuite/gcc.target/aarch64/extend.c | 28 ++++++++++++++++++++++++++++
2 files changed, 29 insertions(+), 1 deletion(-)
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 90bbc57..27b53f4 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -8226,7 +8226,7 @@ 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..19b120d 100644
--- a/gcc/testsuite/gcc.target/aarch64/extend.c
+++ b/gcc/testsuite/gcc.target/aarch64/extend.c
@@ -37,6 +37,13 @@ adddi_uxtw (unsigned long long a, unsigned int i)
}
unsigned long long
+adddi_uxtw4 (unsigned long long a, unsigned int i)
+{
+ /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*uxtw #?4" } } */
+ return a + ((unsigned long long)i << 4);
+}
+
+unsigned long long
adddi_uxtw0 (unsigned long long a, unsigned int i)
{
/* { dg-final { scan-assembler "add\tx\[0-9\]+,.*uxtw\n" } } */
@@ -51,6 +58,13 @@ adddi_sxtw (long long a, int i)
}
long long
+adddi_sxtw4 (long long a, int i)
+{
+ /* { dg-final { scan-assembler "add\tx\[0-9\]+,.*sxtw #?4" } } */
+ return a + ((long long)i << 4);
+}
+
+long long
adddi_sxtw0 (long long a, int i)
{
/* { dg-final { scan-assembler "add\tx\[0-9\]+,.*sxtw\n" } } */
@@ -65,6 +79,13 @@ subdi_uxtw (unsigned long long a, unsigned int i)
}
unsigned long long
+subdi_uxtw4 (unsigned long long a, unsigned int i)
+{
+ /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*uxtw #?4" } } */
+ return a - ((unsigned long long)i << 4);
+}
+
+unsigned long long
subdi_uxtw0 (unsigned long long a, unsigned int i)
{
/* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*uxtw\n" } } */
@@ -79,6 +100,13 @@ subdi_sxtw (long long a, int i)
}
long long
+subdi_sxtw4 (long long a, int i)
+{
+ /* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*sxtw #?4" } } */
+ return a - ((long long)i << 4);
+}
+
+long long
subdi_sxtw0 (long long a, int i)
{
/* { dg-final { scan-assembler "sub\tx\[0-9\]+,.*sxtw\n" } } */
--
2.9.5
