Cope with NULL dw_cfi_cfa_loc

[Alexandre Oliva <oliva@adacore.com>]

In def_cfa_0, we may set the 2nd operand's dw_cfi_cfa_loc to NULL, but
then cfi_oprnd_equal_p calls cfa_equal_p with a NULL dw_cfa_location*.
This patch aranges for us to tolerate NULL dw_cfi_cfa_loc.

Regstrapped on x86_64-linux-gnu.  Ok to install?


for  gcc/ChangeLog

	PR middle-end/104540
	* dwarf2cfi.cc (cfi_oprnd_equal_p): Cope with NULL
	dw_cfi_cfa_loc.

for  gcc/testsuite/ChangeLog

	PR middle-end/104540
	* g++.dg/PR104540.C: New.
---
 gcc/dwarf2cfi.cc                |    3 +++
 gcc/testsuite/g++.dg/pr104540.C |   21 +++++++++++++++++++++
 2 files changed, 24 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/pr104540.C

diff --git a/gcc/dwarf2cfi.cc b/gcc/dwarf2cfi.cc
index 9ca97d7a3bf56..ab7c5cc5b27b5 100644
--- a/gcc/dwarf2cfi.cc
+++ b/gcc/dwarf2cfi.cc
@@ -788,6 +788,9 @@ cfi_oprnd_equal_p (enum dw_cfi_oprnd_type t, dw_cfi_oprnd *a, dw_cfi_oprnd *b)
     case dw_cfi_oprnd_loc:
       return loc_descr_equal_p (a->dw_cfi_loc, b->dw_cfi_loc);
     case dw_cfi_oprnd_cfa_loc:
+      /* If any of them is NULL, don't dereference either.  */
+      if (!a->dw_cfi_cfa_loc || !b->dw_cfi_cfa_loc)
+	return a->dw_cfi_cfa_loc == b->dw_cfi_cfa_loc;
       return cfa_equal_p (a->dw_cfi_cfa_loc, b->dw_cfi_cfa_loc);
     }
   gcc_unreachable ();
diff --git a/gcc/testsuite/g++.dg/pr104540.C b/gcc/testsuite/g++.dg/pr104540.C
new file mode 100644
index 0000000000000..a86ecbfd088c3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr104540.C
@@ -0,0 +1,21 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fharden-conditional-branches -mforce-drap -mstackrealign --param=max-grow-copy-bb-insns=125" } */
+
+char c;
+int i;
+
+void bar(int);
+
+struct S {
+  int mi;
+  long ml;
+  S(int);
+};
+
+
+void foo() {
+  int s = c == 0 ? 1 : 2;
+  bar(s);
+  if (i)
+    S s(0);
+}


-- 
Alexandre Oliva, happy hacker                https://FSFLA.org/blogs/lxo/
   Free Software Activist                       GNU Toolchain Engineer
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>