[PATCH] gas: sframe: fix PR gas/33170

[Indu Bhagat]

SFrame generation code assumes that since DW_CFA_restore means
restoration of the state of the register to the one at the beginning of
the function, there must be a state to restore to (hence the gas_assert
(cie_fre)).

This assumption needs adjustment.  DW_CFA_restore may be present in the
very beginning of a (e.g., cold) function, with no initialized state for
SFrame functions to restore to.

gas/
	PR gas/33170
	* gas/gen-sframe.c (sframe_xlate_do_restore): Use current FRE if
	CIE FRE is not yet setup.
gas/testsuite/
	PR gas/33170
	* gas/cfi-sframe/cfi-sframe.exp: New test.
	* gas/cfi-sframe/cfi-sframe-x86_64-pr33170.d: New test.
	* gas/cfi-sframe/cfi-sframe-x86_64-pr33170.s: New test.
---
 gas/gen-sframe.c                              | 15 +++++--
 .../cfi-sframe/cfi-sframe-x86_64-pr33170.d    | 19 +++++++++
 .../cfi-sframe/cfi-sframe-x86_64-pr33170.s    | 40 +++++++++++++++++++
 gas/testsuite/gas/cfi-sframe/cfi-sframe.exp   |  1 +
 4 files changed, 71 insertions(+), 4 deletions(-)
 create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.d
 create mode 100644 gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.s

diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
index 806ef5f9b5b..079cbdbc1cf 100644
--- a/gas/gen-sframe.c
+++ b/gas/gen-sframe.c
@@ -1286,11 +1286,18 @@ sframe_xlate_do_restore (struct sframe_xlate_ctx *xlate_ctx,
      list of FREs for the specific function.  */
   struct sframe_row_entry *cur_fre = xlate_ctx->cur_fre;
 
+  /* PR gas/33170.  It is valid to have a:
+       .cfi_restore N
+    even at the entry of a function; in that case cie_fre is not yet setup.
+    Point cie_fre to cur_fre, and let the machinery proceed to update
+    merge_candidate as usual.  */
+  if (cie_fre == NULL)
+    cie_fre = cur_fre;
+
   /* Change the rule for the indicated register to the rule assigned to
-     it by the initial_instructions in the CIE.  */
-  gas_assert (cie_fre);
-  /* SFrame FREs track only CFA and FP / RA for backtracing purposes;
-     skip the other .cfi_restore directives.  */
+     it by the initial_instructions in the CIE.  SFrame FREs track only CFA
+     and FP / RA for backtracing purposes; skip the other .cfi_restore
+     directives.  */
   if (cfi_insn->u.r == SFRAME_CFA_FP_REG)
     {
       gas_assert (cur_fre);
diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.d b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.d
new file mode 100644
index 00000000000..85c358fa30f
--- /dev/null
+++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.d
@@ -0,0 +1,19 @@
+#as: --gsframe
+#objdump: --sframe=.sframe
+#name: SFrame generation on x86_64 pr31170
+#...
+Contents of the SFrame section .sframe:
+  Header :
+
+    Version: SFRAME_VERSION_2
+    Flags: SFRAME_F_FDE_FUNC_START_PCREL
+    CFA fixed RA offset: \-8
+    Num FDEs: 1
+    Num FREs: 2
+
+  Function Index :
+
+    func idx \[0\]: pc = 0x0, size = 50 bytes
+    STARTPC +CFA +FP +RA +
+    0+0000 +fp\+16 +c\-16 +f +
+    0+002d +fp\+16 +c\-16 +f +
diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.s b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.s
new file mode 100644
index 00000000000..e1311084c9f
--- /dev/null
+++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe-x86_64-pr33170.s
@@ -0,0 +1,40 @@
+# PR gas/33170
+# Ennsure graceful handling.
+        .section  .text.unlikely
+        .cfi_startproc
+        .type    XZ.cold, @function
+XZ.cold:
+.L1:
+        .cfi_def_cfa 6, 16
+        .cfi_offset 3, -56
+        .cfi_offset 6, -16
+        .cfi_offset 12, -48
+        .cfi_offset 13, -40
+        .cfi_offset 14, -32
+        .cfi_offset 15, -24
+.L2:
+        .cfi_restore 12
+        .cfi_restore 13
+        movl   $56, %esi
+        movq   %r14, %rdi
+        call   _Z@PLT
+        movq   %r12, -32(%rbp)
+        movq   %r13, -24(%rbp)
+        movq   %r14, -16(%rbp)
+        movq   %r15, -8(%rbp)
+        .cfi_offset 12, -48
+        .cfi_offset 13, -40
+        .cfi_offset 14, -32
+        .cfi_offset 15, -24
+        jne    .L3
+        movq   %rbx, %rdi
+        call   bar@PLT
+.L3:
+        movq   -32(%rbp), %r12
+        .cfi_remember_state
+        .cfi_restore 12
+        jmp    .L4
+.L4:
+        .cfi_restore_state
+        call   _ZF@PLT
+        .cfi_endproc
diff --git a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
index 00a3ecc067c..82669cd0475 100644
--- a/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
+++ b/gas/testsuite/gas/cfi-sframe/cfi-sframe.exp
@@ -58,6 +58,7 @@ if { [istarget "x86_64-*-*"] && [gas_sframe_check] } then {
 	set ASFLAGS "$ASFLAGS --64"
 	run_dump_test "cfi-sframe-x86_64-1"
 	run_dump_test "cfi-sframe-x86_64-2"
+	run_dump_test "cfi-sframe-x86_64-pr33170"
 	run_dump_test "cfi-sframe-x86_64-empty-1"
 	run_dump_test "cfi-sframe-x86_64-empty-2"
 	run_dump_test "cfi-sframe-x86_64-empty-3"
-- 
2.43.0