On 6/23/25 12:01 AM, Alexandre Oliva wrote:
When attempting to bootstrap arm-linux-gnueabihf with
{BOOT_C,T}FLAGS='-g -O2 -fnon-call-exceptions
-fstack-clash-protection', gmp fails to build in stage2: gen-fac's
mpz_and gets miscompiled.
A pseudo is initialized before a loop and used in a PRE_INC load
inside a loop. It gets spilled just as the fp2sp elimination is
disabled, and only the initialization gets adjusted with elimination
offsets. The unadjusted stack slot within the PRE_INC load ends up
reloaded later, but only when the FP offset has already missed its
chance to be adjusted.
Arrange for lra_eliminate_regs_1 to adjust autoinc addresses that are
MEMs themselves.
Regstrapped on x86_64-linux-gnu, bootstrapped on arm-linux-gnueabihf
(arm and thumb modes), also tested with gcc-14 on arm-vx7r2 and
arm-linux-gnueabihf. Ok to install?
Yes. Thank you, Alex
for gcc/ChangeLog
PR rtl-optimization/120424
* lra_eliminations.cc (lra_eliminate_regs_1): Adjust autoinc
addresses that are MEMs.
---
gcc/lra-eliminations.cc | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/gcc/lra-eliminations.cc b/gcc/lra-eliminations.cc
index 5713a96805233..9cdd0c5ff53a2 100644
--- a/gcc/lra-eliminations.cc
+++ b/gcc/lra-eliminations.cc
@@ -571,6 +571,9 @@ lra_eliminate_regs_1 (rtx_insn *insn, rtx x, machine_mode
mem_mode,
case POST_INC:
case PRE_DEC:
case POST_DEC:
+ /* Recurse to adjust elimination offsets in a spilled pseudo. */
+ if (GET_CODE (XEXP (x, 0)) == MEM)
+ break;
/* We do not support elimination of a register that is modified.
elimination_effects has already make sure that this does not
happen. */
@@ -578,6 +581,9 @@ lra_eliminate_regs_1 (rtx_insn *insn, rtx x, machine_mode
mem_mode,
case PRE_MODIFY:
case POST_MODIFY:
+ /* Recurse to adjust elimination offsets in a spilled pseudo. */
+ if (GET_CODE (XEXP (x, 0)) == MEM)
+ break;
/* We do not support elimination of a hard register that is
modified. LRA has already make sure that this does not
happen. The only remaining case we need to consider here is
