When computing an address plus a large offset on riscv64 with a
PC-relative sequence, we may hit the range limit for auipc and get a
relocation overflow, where on riscv32 the computation wraps around.
Since -mcmodel=medany requires the entire program to fit in a 2GiB
address range, a +/-1GiB+ offset added to an in-range symbol in a
barely-fitting program is more likely than not to be out-of-range.
Since such large constants are unlikely to come up by chance, separate
them from the symbol so as to avoid the relocation overflow.
Tested on riscv64-elf and riscv32-elf with gcc-14; now testing on trunk.
Ok to install, or should we go for some more flexible alternative, say
with a --param to customize the offset range limit?
for gcc/ChangeLog
PR target/91420
* config/riscv/riscv.cc (riscv_symbolic_constant_p): Require
offsets smaller than +/- 1GiB for PCREL symbols.
for gcc/testsuite/ChangeLog
PR target/91420
* gcc.target/riscv/pr91420.c: New.
---
gcc/config/riscv/riscv.cc | 13 ++++++++
gcc/testsuite/gcc.target/riscv/pr91420.c | 46 ++++++++++++++++++++++++++++++
2 files changed, 58 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.target/riscv/pr91420.c
diff --git a/gcc/config/riscv/riscv.cc b/gcc/config/riscv/riscv.cc
index d5de76c342e0c..e62ab6e8bee93 100644
--- a/gcc/config/riscv/riscv.cc
+++ b/gcc/config/riscv/riscv.cc
@@ -1736,8 +1736,19 @@ riscv_symbolic_constant_p (rtx x, enum riscv_symbol_type
*symbol_type)
/* Nonzero offsets are only valid for references that don't use the GOT. */
switch (*symbol_type)
{
- case SYMBOL_ABSOLUTE:
case SYMBOL_PCREL:
+ /* In 64-bit mode, PC-relative offsets with ranges beyond +/-1GiB are
+ more likely than not to end up out of range for an auipc instruction
+ randomly-placed within the 2GB range usable by medany, and such
+ offsets are quite unlikely to come up by chance, so be conservative
+ and separate the offset for them when in 64-bit mode, where they don't
+ wrap around. */
+ if (TARGET_64BIT)
+ return sext_hwi (INTVAL (offset), 30) == INTVAL (offset);
+
+ /* Fall through. */
+
+ case SYMBOL_ABSOLUTE:
case SYMBOL_TLS_LE:
/* GAS rejects offsets outside the range [-2^31, 2^31-1]. */
return sext_hwi (INTVAL (offset), 32) == INTVAL (offset);
diff --git a/gcc/testsuite/gcc.target/riscv/pr91420.c
b/gcc/testsuite/gcc.target/riscv/pr91420.c
new file mode 100644
index 0000000000000..936d998a66307
--- /dev/null
+++ b/gcc/testsuite/gcc.target/riscv/pr91420.c
@@ -0,0 +1,46 @@
+/* { dg-do assemble } */
+/* { dg-options "-O2 -mcmodel=medany -save-temps" } */
+
+int a[1];
+
+__UINTPTR_TYPE__
+foo(void)
+{
+ return (__UINTPTR_TYPE__)a + 0x7fffffff;
+}
+
+__UINTPTR_TYPE__
+bfoo(void)
+{
+ return (__UINTPTR_TYPE__)a + 0x40000000;
+}
+
+__UINTPTR_TYPE__
+sfoo(void)
+{
+ return (__UINTPTR_TYPE__)a + 0x3fffffff;
+}
+
+__UINTPTR_TYPE__
+bar(void)
+{
+ return (__UINTPTR_TYPE__)a - 0x80000000;
+}
+
+__UINTPTR_TYPE__
+bbar(void)
+{
+ return (__UINTPTR_TYPE__)a - 0x40000000;
+}
+
+__UINTPTR_TYPE__
+sbar(void)
+{
+ return (__UINTPTR_TYPE__)a - 0x3fffffff;
+}
+
+/* /* dg-final { scan-assembler-times "lla\ta[0-9]*, a$" 4 { target
riscv64-*-* } } } */
+/* /* dg-final { scan-assembler-times "lla\ta[0-9]*, a[-+]" 2 { target
riscv64-*-* } } } */
+
+/* /* dg-final { scan-assembler-times "lla\ta[0-9]*, a[-+]$" 6 { target
riscv32-*-* } } } */
+/* /* dg-final { scan-assembler-not "lla\ta[0-9]*, a$" { target riscv32-*-* }
} } */
--
Alexandre Oliva, happy hacker https://blog.lx.oliva.nom.br/
Free Software Activist FSFLA co-founder GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity.
Excluding neuro-others for not behaving ""normal"" is *not* inclusive!
