Improves the code generation by getting rid of redundant LAs, as seen
in the following example:
- la %r1,0(%r13)
- lg %r4,0(%r1)
+ lg %r4,0(%r13)
Also allows to proceed with the merge of movdi_64 and movdi_larl.
Currently LRA decides to spill literal pool references back to the
literal pool, because it preliminarily chooses alternatives with
CT_MEMORY constraints without calling
satisfies_memory_constraint_p (). Later on it notices that the
constraint is wrong and fixes it by spilling. The constraint in this
case is "b", and the operand is a literal pool reference. There is
no reason to reject them. The current behavior was introduced,
apparently unintentionally, by
https://gcc.gnu.org/ml/gcc-patches/2010-09/msg00812.html
The patch affects a little bit more than mentioned in the subject,
because it changes s390_loadrelative_operand_p (), which is called not
only for checking the "b" constraint. However, the only caller for
which it should really not accept literal pool references is
s390_check_qrst_address (), so it was changed to explicitly do so.
gcc/ChangeLog:
2018-10-18 Ilya Leoshkevich <i...@linux.ibm.com>
* config/s390/s390.c (s390_loadrelative_operand_p): Accept
literal pool references.
(s390_check_qrst_address): Adapt to the new behavior of
s390_loadrelative_operand_p ().
gcc/testsuite/ChangeLog:
2018-10-18 Ilya Leoshkevich <i...@linux.ibm.com>
* gcc.target/s390/litpool-int.c: New test.
---
gcc/config/s390/s390.c | 9 +++++----
gcc/testsuite/gcc.target/s390/litpool-int.c | 12 ++++++++++++
2 files changed, 17 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/s390/litpool-int.c
diff --git a/gcc/config/s390/s390.c b/gcc/config/s390/s390.c
index ed307c3598b..0b7e44b62e1 100644
--- a/gcc/config/s390/s390.c
+++ b/gcc/config/s390/s390.c
@@ -3110,8 +3110,7 @@ s390_legitimate_address_without_index_p (rtx op)
Valid addresses are single references or a sum of a reference and a
constant integer. Return these parts in SYMREF and ADDEND. You can
pass NULL in REF and/or ADDEND if you are not interested in these
- values. Literal pool references are *not* considered symbol
- references. */
+ values. */
static bool
s390_loadrelative_operand_p (rtx addr, rtx *symref, HOST_WIDE_INT *addend)
@@ -3130,7 +3129,7 @@ s390_loadrelative_operand_p (rtx addr, rtx *symref,
HOST_WIDE_INT *addend)
addr = XEXP (addr, 0);
}
- if ((GET_CODE (addr) == SYMBOL_REF && !CONSTANT_POOL_ADDRESS_P (addr))
+ if (GET_CODE (addr) == SYMBOL_REF
|| (GET_CODE (addr) == UNSPEC
&& (XINT (addr, 1) == UNSPEC_GOTENT
|| XINT (addr, 1) == UNSPEC_PLT)))
@@ -3153,6 +3152,7 @@ s390_loadrelative_operand_p (rtx addr, rtx *symref,
HOST_WIDE_INT *addend)
static int
s390_check_qrst_address (char c, rtx op, bool lit_pool_ok)
{
+ rtx symref;
struct s390_address addr;
bool decomposed = false;
@@ -3161,7 +3161,8 @@ s390_check_qrst_address (char c, rtx op, bool lit_pool_ok)
/* This check makes sure that no symbolic address (except literal
pool references) are accepted by the R or T constraints. */
- if (s390_loadrelative_operand_p (op, NULL, NULL))
+ if (s390_loadrelative_operand_p (op, &symref, NULL)
+ && (!lit_pool_ok || !CONSTANT_POOL_ADDRESS_P (symref)))
return 0;
/* Ensure literal pool references are only accepted if LIT_POOL_OK. */
diff --git a/gcc/testsuite/gcc.target/s390/litpool-int.c
b/gcc/testsuite/gcc.target/s390/litpool-int.c
new file mode 100644
index 00000000000..a6bf0c01f4f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/s390/litpool-int.c
@@ -0,0 +1,12 @@
+/* Test that we do not generate useless LAs. */
+
+/* { dg-do compile } */
+/* { dg-options "-march=z10 -O1" } */
+
+int a;
+
+void b()
+{
+ a /= 100;
+ /* { dg-final { scan-assembler-not {(?n)\n\tla\t%r\d+,.+\(%r13\)\n} } } */
+}
--
2.19.0
