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* [gcc(refs/users/aoliva/heads/testme)] Reject unaligned subregs when strict alignment is required
@ 2022-05-05 2:42 Alexandre Oliva
0 siblings, 0 replies; 2+ messages in thread
From: Alexandre Oliva @ 2022-05-05 2:42 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:3d8a853f35a2a5e259d84c26580224d4d1de10e8
commit 3d8a853f35a2a5e259d84c26580224d4d1de10e8
Author: Alexandre Oliva <oliva@adacore.com>
Date: Wed May 4 23:41:39 2022 -0300
Reject unaligned subregs when strict alignment is required
The testcase for pr100106, compiled with optimization for 32-bit
powerpc -mcpu=604 with -mstrict-align expands the initialization of a
union from a float _Complex value into a load from an SCmode
constant pool entry, aligned to 4 bytes, into a DImode pseudo,
requiring 8-byte alignment.
The patch that introduced the testcase modified simplify_subreg to
avoid changing the MEM to outermode, but simplify_gen_subreg still
creates a SUBREG or a MEM that would require stricter alignment than
MEM's, and lra_constraints appears to get confused by that, repeatedly
creating unsatisfiable reloads for the SUBREG until it exceeds the
insn count.
Avoiding the unaligned SUBREG, expand splits the DImode dest into
SUBREGs and loads each SImode word of the constant pool with the
proper alignment.
for gcc/ChangeLog
PR target/100106
* emit-rtl.c (validate_subreg): Reject a SUBREG of a MEM that
requires stricter alignment than MEM's.
for gcc/testsuite/ChangeLog
PR target/100106
* gcc.target/powerpc/pr100106-sa.c: New.
TN: V502-036
Diff:
---
gcc/emit-rtl.cc | 3 +++
gcc/testsuite/gcc.target/powerpc/pr100106-sa.c | 4 ++++
2 files changed, 7 insertions(+)
diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index 1e02ae254d0..642e47eada0 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -982,6 +982,9 @@ validate_subreg (machine_mode omode, machine_mode imode,
return subreg_offset_representable_p (regno, imode, offset, omode);
}
+ else if (reg && MEM_P (reg)
+ && STRICT_ALIGNMENT && MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (omode))
+ return false;
/* The outer size must be ordered wrt the register size, otherwise
we wouldn't know at compile time how many registers the outer
diff --git a/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c b/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c
new file mode 100644
index 00000000000..1cd6b595a5b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c
@@ -0,0 +1,4 @@
+/* { dg-do compile } */
+/* { dg-options "-mcpu=604 -O -mstrict-align" } */
+
+#include "../../gcc.c-torture/compile/pr100106.c"
^ permalink raw reply [flat|nested] 2+ messages in thread
* [gcc(refs/users/aoliva/heads/testme)] Reject unaligned subregs when strict alignment is required
@ 2022-05-05 6:31 Alexandre Oliva
0 siblings, 0 replies; 2+ messages in thread
From: Alexandre Oliva @ 2022-05-05 6:31 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:b119a4098423b7c6bf4dcc2fdc59efb95c79d570
commit b119a4098423b7c6bf4dcc2fdc59efb95c79d570
Author: Alexandre Oliva <oliva@adacore.com>
Date: Wed May 4 23:41:39 2022 -0300
Reject unaligned subregs when strict alignment is required
The testcase for pr100106, compiled with optimization for 32-bit
powerpc -mcpu=604 with -mstrict-align expands the initialization of a
union from a float _Complex value into a load from an SCmode
constant pool entry, aligned to 4 bytes, into a DImode pseudo,
requiring 8-byte alignment.
The patch that introduced the testcase modified simplify_subreg to
avoid changing the MEM to outermode, but simplify_gen_subreg still
creates a SUBREG or a MEM that would require stricter alignment than
MEM's, and lra_constraints appears to get confused by that, repeatedly
creating unsatisfiable reloads for the SUBREG until it exceeds the
insn count.
Avoiding the unaligned SUBREG, expand splits the DImode dest into
SUBREGs and loads each SImode word of the constant pool with the
proper alignment.
for gcc/ChangeLog
PR target/100106
* emit-rtl.c (validate_subreg): Reject a SUBREG of a MEM that
requires stricter alignment than MEM's.
for gcc/testsuite/ChangeLog
PR target/100106
* gcc.target/powerpc/pr100106-sa.c: New.
Diff:
---
gcc/emit-rtl.cc | 3 +++
gcc/testsuite/gcc.target/powerpc/pr100106-sa.c | 4 ++++
2 files changed, 7 insertions(+)
diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index 1e02ae254d0..642e47eada0 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -982,6 +982,9 @@ validate_subreg (machine_mode omode, machine_mode imode,
return subreg_offset_representable_p (regno, imode, offset, omode);
}
+ else if (reg && MEM_P (reg)
+ && STRICT_ALIGNMENT && MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (omode))
+ return false;
/* The outer size must be ordered wrt the register size, otherwise
we wouldn't know at compile time how many registers the outer
diff --git a/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c b/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c
new file mode 100644
index 00000000000..6cc29595c8b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr100106-sa.c
@@ -0,0 +1,4 @@
+/* { dg-do compile { target { ilp32 } } } */
+/* { dg-options "-mcpu=604 -O -mstrict-align" } */
+
+#include "../../gcc.c-torture/compile/pr100106.c"
^ permalink raw reply [flat|nested] 2+ messages in thread
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