middle-end: Fix malloc like functions when calling with void "return" [PR120024]

When expanding malloc like functions, we copy the return register into a temporary
and then mark that temporary register with a noalias regnote and the alignment.
This works fine unless you are calling the function with a return type of void.
At this point then the valreg will be null and a crash will happen.

A few cleanups are included in this patch because it was easier to do the fix
with the cleanups added.
The start_sequence/end_sequence for ECF_MALLOC is no longer needed; I can't tell
if it was ever needed.
The emit_move_insn function returns the last emitted instruction anyways so
there is no reason to call get_last_insn as we can just use the return value
of emit_move_insn. This has been true since this code was originally added
so I don't understand why it was done that way beforehand.

Bootstrapped and tested on x86_64-linux-gnu.

	PR middle-end/120024

gcc/ChangeLog:

	* calls.cc (expand_call): Remove start_sequence/end_sequence
	for ECF_MALLOC.
	Check valreg before deferencing it when it comes to malloc like
	functions. Use the return value of emit_move_insn instead of
	calling get_last_insn.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/malloc-1.c: New test.
	* gcc.dg/torture/malloc-2.c: New test.

Signed-off-by: Andrew Pinski <andrew.pinski@oss.qualcomm.com>

3 files changed, 28 insertions, 13 deletions

diff --git a/gcc/calls.cc b/gcc/calls.cc
index 2711c4e..bb8a6d0 100644
--- a/gcc/calls.cc
+++ b/gcc/calls.cc
@@ -3235,11 +3235,6 @@ expand_call (tree exp, rtx target, int ignore)
       if (pass)
 	precompute_arguments (num_actuals, args);
 
-      /* Now we are about to start emitting insns that can be deleted
-	 if a libcall is deleted.  */
-      if (pass && (flags & ECF_MALLOC))
-	start_sequence ();
-
       /* Check the canary value for sibcall or function which doesn't
 	 return and could throw.  */
       if ((pass == 0
@@ -3771,25 +3766,23 @@ expand_call (tree exp, rtx target, int ignore)
 	  valreg = gen_rtx_REG (TYPE_MODE (rettype), REGNO (valreg));
 	}
 
-      if (pass && (flags & ECF_MALLOC))
+      /* If the return register exists, for malloc like
+	 function calls, mark the return register with the
+	 alignment and noalias reg note.  */
+      if (pass && (flags & ECF_MALLOC) && valreg)
 	{
 	  rtx temp = gen_reg_rtx (GET_MODE (valreg));
-	  rtx_insn *last, *insns;
+	  rtx_insn *last;
 
 	  /* The return value from a malloc-like function is a pointer.  */
 	  if (TREE_CODE (rettype) == POINTER_TYPE)
 	    mark_reg_pointer (temp, MALLOC_ABI_ALIGNMENT);
 
-	  emit_move_insn (temp, valreg);
+	  last = emit_move_insn (temp, valreg);
 
 	  /* The return value from a malloc-like function cannot alias
 	     anything else.  */
-	  last = get_last_insn ();
 	  add_reg_note (last, REG_NOALIAS, temp);
-
-	  /* Write out the sequence.  */
-	  insns = end_sequence ();
-	  emit_insn (insns);
 	  valreg = temp;
 	}
 
diff --git a/gcc/testsuite/gcc.dg/torture/malloc-1.c b/gcc/testsuite/gcc.dg/torture/malloc-1.c
new file mode 100644
index 0000000..ba24153
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/malloc-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* PR middle-end/120024 */
+
+void *f(unsigned) __attribute__((malloc));
+void g()
+{
+  void *(*g)(unsigned) = f;
+  void (*h)(unsigned) = (void (*)(unsigned))g;
+  h(1);
+}
diff --git a/gcc/testsuite/gcc.dg/torture/malloc-2.c b/gcc/testsuite/gcc.dg/torture/malloc-2.c
new file mode 100644
index 0000000..8eeca9d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/malloc-2.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* PR middle-end/120024 */
+
+void *f(unsigned) __attribute__((malloc));
+void h1(void);
+void g(void)
+{
+  void *(*g)(unsigned) = f;
+  void (*h)(unsigned) = (void (*)(unsigned))g;
+  h(1);
+  h1();
+}