This patch fixes a bug in which the function prologue would save more
registers to the stack than there was space allocated. This would cause
data corruption when the epilogue restored the registers if a child
function had overwritten that memory.
The problem was caused by insn constraints that allow vectors to be
placed in scalar registers. This isn't usually allowed without an
explicit vec_duplicate in the pattern, but some post-reload splitters do
it sometimes (hence the size calculation mismatch).
A full fix would add vec_duplicate variants of all the instructions that
support this, but that's a huge explosion of patterns, and this fix is
enough for correctness, for now.
This has already been committed to the OG12 branch.
Andrew
amdgcn: Fix register size bug
Fix an issue in which "vectors" of duplicate entries placed in scalar
registers caused the following 63 registers to be marked live, for the
purpose of prologue generation, which resulted in stack corruption.
gcc/ChangeLog:
* config/gcn/gcn.cc (gcn_class_max_nregs): Handle vectors in SGPRs.
(move_callee_saved_registers): Detect the bug condition early.
diff --git a/gcc/config/gcn/gcn.cc b/gcc/config/gcn/gcn.cc
index 5bf88e98083..a7d278cd2f8 100644
--- a/gcc/config/gcn/gcn.cc
+++ b/gcc/config/gcn/gcn.cc
@@ -492,6 +492,15 @@ gcn_class_max_nregs (reg_class_t rclass, machine_mode mode)
}
else if (rclass == VCC_CONDITIONAL_REG && mode == BImode)
return 2;
+
+ /* Vector modes in SGPRs are not supposed to happen (disallowed by
+ gcn_hard_regno_mode_ok), but there are some patterns that have an "Sv"
+ constraint and are used by splitters, post-reload.
+ This ensures that we don't accidentally mark the following 63 scalar
+ registers as "live". */
+ if (rclass == SGPR_REGS && VECTOR_MODE_P (mode))
+ return CEIL (GET_MODE_SIZE (GET_MODE_INNER (mode)), 4);
+
return CEIL (GET_MODE_SIZE (mode), 4);
}
@@ -3239,6 +3248,10 @@ move_callee_saved_registers (rtx sp, machine_function
*offsets,
emit_insn (move_vectors);
emit_insn (move_scalars);
}
+
+ /* This happens when a new register becomes "live" after reload.
+ Check your splitters! */
+ gcc_assert (offset <= offsets->callee_saves);
}
/* Generate prologue. Called from gen_prologue during pro_and_epilogue pass.
