Hi,
Many thanks for reviewing. Please find the updated patch. The explicit
calls to gen_rtx_PLUS and GEN_INT have been replaced by plus_constant,
and the call to aarch64_set_frame_expr has been replaced with
add_reg_note (REG_CFA_ADJUST_CFA).
I'll clean up other cases in aarch64.c in a separate patch.
OK to commit?
Thanks,
Yufeng
gcc/ChangeLog
2012-11-06 Yufeng Zhang <yufeng.zh...@arm.com>
* config/aarch64/aarch64.c (aarch64_expand_prologue): For the
load-pair with writeback instruction, replace
aarch64_set_frame_expr with add_reg_note (REG_CFA_ADJUST_CFA);
add new local variable 'cfa_reg' and use it.
gcc/testsuite/ChangeLog
2012-11-06 Yufeng Zhang <yufeng.zh...@arm.com>
* gcc.target/aarch64/dwarf-cfa-reg.c: New file.
On 09/12/12 19:37, Richard Henderson wrote:
On 09/12/2012 09:10 AM, Yufeng Zhang wrote:
aarch64_set_frame_expr (gen_rtx_SET
(Pmode,
stack_pointer_rtx,
- gen_rtx_PLUS (Pmode, stack_pointer_rtx,
+ gen_rtx_PLUS (Pmode, cfa_reg,
GEN_INT (offset))));
We'd prefer to use
plus_constant (Pmode, cfa_reg, offset)
instead of the explicit call to gen_rtx_PLUS and GEN_INT.
It would appear that the entire aarch64.c file ought to
be audited for that.
Also, use of the REG_CFA_* notes is strongly encouraged over
use of REG_FRAME_RELATED_EXPR.
There's all sorts of work involved in turning R_F_R_E into
R_CFA_* notes, depending on a rather large state machine.
This state machine was developed when only prologues were
annotated for unwinding, and therefore one cannot expect it
to work reliably for epilogues.
A long-term goal is to convert all targets to use R_CFA_*
exclusively, as that preserves much more information present
in the structure of the code of the prologue generator. It
means less work within the compiler, and eventually being able
to remove a rather large hunk of state-machine code.
r~
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index b36be90..8a2d7ba 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -1777,7 +1777,7 @@ aarch64_expand_prologue (void)
- original_frame_size
- cfun->machine->frame.saved_regs_size);
- /* Store pairs and load pairs have a range only of +/- 512. */
+ /* Store pairs and load pairs have a range only -512 to 504. */
if (offset >= 512)
{
/* When the frame has a large size, an initial decrease is done on
@@ -1923,6 +1923,7 @@ aarch64_expand_epilogue (bool for_sibcall)
HOST_WIDE_INT original_frame_size, frame_size, offset;
HOST_WIDE_INT fp_offset;
rtx insn;
+ rtx cfa_reg;
aarch64_layout_frame ();
original_frame_size = get_frame_size () + cfun->machine->saved_varargs_size;
@@ -1935,7 +1936,9 @@ aarch64_expand_epilogue (bool for_sibcall)
- original_frame_size
- cfun->machine->frame.saved_regs_size);
- /* Store pairs and load pairs have a range only of +/- 512. */
+ cfa_reg = frame_pointer_needed ? hard_frame_pointer_rtx : stack_pointer_rtx;
+
+ /* Store pairs and load pairs have a range only -512 to 504. */
if (offset >= 512)
{
offset = original_frame_size + cfun->machine->frame.saved_regs_size;
@@ -1966,6 +1969,10 @@ aarch64_expand_epilogue (bool for_sibcall)
hard_frame_pointer_rtx,
GEN_INT (- fp_offset)));
RTX_FRAME_RELATED_P (insn) = 1;
+ /* As SP is set to (FP - fp_offset), according to the rules in
+ dwarf2cfi.c:dwarf2out_frame_debug_expr, CFA should be calculated
+ from the value of SP from now on. */
+ cfa_reg = stack_pointer_rtx;
}
aarch64_save_or_restore_callee_save_registers
@@ -2003,11 +2010,9 @@ aarch64_expand_epilogue (bool for_sibcall)
GEN_INT (offset),
GEN_INT (GET_MODE_SIZE (DImode) + offset)));
RTX_FRAME_RELATED_P (XVECEXP (PATTERN (insn), 0, 2)) = 1;
- aarch64_set_frame_expr (gen_rtx_SET
- (Pmode,
- stack_pointer_rtx,
- gen_rtx_PLUS (Pmode, stack_pointer_rtx,
- GEN_INT (offset))));
+ add_reg_note (insn, REG_CFA_ADJUST_CFA,
+ (gen_rtx_SET (Pmode, stack_pointer_rtx,
+ plus_constant (cfa_reg, offset))));
}
/* The first part of a frame-related parallel insn
@@ -2027,7 +2032,6 @@ aarch64_expand_epilogue (bool for_sibcall)
RTX_FRAME_RELATED_P (insn) = 1;
}
}
-
else
{
insn = emit_insn (gen_add2_insn (stack_pointer_rtx,
diff --git a/gcc/testsuite/gcc.target/aarch64/dwarf-cfa-reg.c
b/gcc/testsuite/gcc.target/aarch64/dwarf-cfa-reg.c
new file mode 100644
index 0000000..cce8815
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/dwarf-cfa-reg.c
@@ -0,0 +1,14 @@
+/* Verify that CFA register is restored to SP after FP is restored. */
+/* { dg-do compile } */
+/* { dg-options "-O0 -gdwarf-2" } */
+/* { dg-final { scan-assembler ".cfi_restore 30" } } */
+/* { dg-final { scan-assembler ".cfi_restore 29" } } */
+/* { dg-final { scan-assembler ".cfi_def_cfa 31, 0" } } */
+/* { dg-final { scan-assembler "ret" } } */
+
+int bar (unsigned int);
+
+int foo (void)
+{
+ return bar (0xcafe);
+}
