[PATCH] Improve debugging info (PR debug/53948 P1 regression)

[Jeff Law <law at redhat dot com>]

Based on feedback from Jakub, I updated the testcase for this PR. 
Updated patch attached.

Installed onto the trunk.

Jeff
commit 48b3095f4ef7da1a06ad2fa96db3967762ce4f0b
Author: Jeff Law <law@redhat.com>
Date:   Fri Feb 8 09:57:43 2013 -0700

           PR debug/53948
            * emit-rtl.c (reg_is_parm_p): New function.
            * regs.h (reg_is_parm_p): New prototype.
            * ira-conflicts.c (ira_build_conflicts): Allow parameters in
            callee-clobbered registers.
    
           PR debug/53948
            * gcc.dg/debug/dwarf2/pr53948.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 9d66888..2693b7e 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2013-02-08  Jeff Law  <law@redhat.com>
+
+	PR debug/53948
+	* emit-rtl.c (reg_is_parm_p): New function.
+	* regs.h (reg_is_parm_p): New prototype.
+	* ira-conflicts.c (ira_build_conflicts): Allow parameters in
+	callee-clobbered registers.
+
 2013-02-08  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	PR target/56043
diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index f997e5d..2c70fb1 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -919,6 +919,18 @@ gen_reg_rtx (enum machine_mode mode)
   return val;
 }
 
+/* Return TRUE if REG is a PARM_DECL, FALSE otherwise.  */
+
+bool
+reg_is_parm_p (rtx reg)
+{
+  tree decl;
+
+  gcc_assert (REG_P (reg));
+  decl = REG_EXPR (reg);
+  return (decl && TREE_CODE (decl) == PARM_DECL);
+}
+
 /* Update NEW with the same attributes as REG, but with OFFSET added
    to the REG_OFFSET.  */
 
diff --git a/gcc/ira-conflicts.c b/gcc/ira-conflicts.c
index 711db0f..710986b 100644
--- a/gcc/ira-conflicts.c
+++ b/gcc/ira-conflicts.c
@@ -895,8 +895,12 @@ ira_build_conflicts (void)
 
 	  if ((! flag_caller_saves && ALLOCNO_CALLS_CROSSED_NUM (a) != 0)
 	      /* For debugging purposes don't put user defined variables in
-		 callee-clobbered registers.  */
-	      || (optimize == 0 && REG_USERVAR_P (allocno_reg)))
+		 callee-clobbered registers.  However, do allow parameters
+		 in callee-clobbered registers to improve debugging.  This
+		 is a bit of a fragile hack.  */
+	      || (optimize == 0
+		  && REG_USERVAR_P (allocno_reg)
+		  && ! reg_is_parm_p (allocno_reg)))
 	    {
 	      IOR_HARD_REG_SET (OBJECT_TOTAL_CONFLICT_HARD_REGS (obj),
 				call_used_reg_set);
diff --git a/gcc/regs.h b/gcc/regs.h
index 0532d08..090d6b6 100644
--- a/gcc/regs.h
+++ b/gcc/regs.h
@@ -89,6 +89,8 @@ REG_N_SETS (int regno)
 #define SET_REG_N_SETS(N,V) (regstat_n_sets_and_refs[N].sets = V)
 #define INC_REG_N_SETS(N,V) (regstat_n_sets_and_refs[N].sets += V)
 
+/* Given a REG, return TRUE if the reg is a PARM_DECL, FALSE otherwise.  */
+extern bool reg_is_parm_p (rtx);
 
 /* Functions defined in regstat.c.  */
 extern void regstat_init_n_sets_and_refs (void);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 583e7d5..83843b7 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2013-02-08  Jeff Law  <law@redhat.com>
+
+	PR debug/53948
+	* gcc.dg/debug/dwarf2/pr53948.c: New test.
+
 2013-02-08  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	PR target/56043
diff --git a/gcc/testsuite/gcc.dg/debug/dwarf2/pr53948.c b/gcc/testsuite/gcc.dg/debug/dwarf2/pr53948.c
new file mode 100644
index 0000000..f0600b7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/debug/dwarf2/pr53948.c
@@ -0,0 +1,10 @@
+/* Test that we have line information for the line
+   with local variable initializations.  */
+/* { dg-options "-O0 -g -dA" } */
+/* { dg-final { scan-assembler ".loc 1 8 0|# line 8" } } */
+
+
+int f (register int a, register int b) {
+  register int x = b, y = a;
+  return x + y; }
+