This patch fixes a bug in the AArch64 epilogue expander which failed to
generate consistent information of REG_FRAME_RELATED_EXPR reg notes in
some cases; for instance, given the following C source code:
int bar (unsigned int);
int foo (void)
{
return bar (0xcafe);
}
------------------- CUT -------------------
The -O0 -g code gen for the function 'foo' is:
.cfi_startproc
stp x29, x30, [sp, -16]!
.LCFI0:
.cfi_def_cfa_offset 16
.cfi_offset 29, -16
.cfi_offset 30, -8
add x29, sp, 0
.LCFI1:
.cfi_def_cfa_register 29
.LM2:
mov w0, 57005
bl bar
.LM3:
ldp x29, x30, [sp], 16
.cfi_restore 30
.cfi_restore 29
ret
.cfi_endproc
------------------- CUT -------------------
As can be seen, the CFA reg is X29 from the ADD instruction until the
end of the func; this is wrong as the LDP instruction restores X29;
the CFA reg should be set to SP after LDP.
The patch passes the gcc and g++ testsuites. Is it OK for the aarch64
branch?
Thanks,
Yufeng
gcc/ChangeLog
2012-09-12 Yufeng Zhang <yufeng.zh...@arm.com>
* config/aarch64/aarch64.c (aarch64_expand_prologue): Add new local
variable 'cfa_reg' and replace stack_pointer_rtx with it in the
REG_FRAME_RELATED_EXPR reg note for the load-pair with writeback
instruction.
gcc/testsuite/ChangeLog
2012-09-12 Yufeng Zhang <yufeng.zh...@arm.com>
* gcc.target/aarch64/dwarf-cfa-reg.c: New file.diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 2d7eba7..f452d3d 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -1786,7 +1786,7 @@ 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
@@ -1934,6 +1934,7 @@ 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;
@@ -1946,7 +1947,9 @@ 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;
@@ -1977,6 +1980,10 @@ 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
@@ -2016,10 +2023,15 @@ 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;
+ /* The REG_FRAME_RELATED_EXPR to be attached to the above insn
+ is either SP = SP + offset or SP = FP + offset, depending on
+ which register had been used to calculate the CFA before
+ the insn; note that FP had the same value as SP before the
+ above insn. */
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))));
}
@@ -2040,7 +2052,6 @@ 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);
+}
