[PATCH][debug] Fix pre_dec handling in vartrack

[Tom de Vries <tdevries at suse dot de>]

Hi,

when compiling test-case gcc.target/i386/vartrack-1.c with -O1 -g, register bx
is pushed in the prologue and popped in the epilogue:
...
(insn/f 26 3 27 2
  (set (mem:DI (pre_dec:DI (reg/f:DI 7 sp)) [0  S8 A8])
       (reg:DI 3 bx))
   "vartrack-1.c":10 61 {*pushdi2_rex64}
   (expr_list:REG_DEAD (reg:DI 3 bx) (nil)))
  ...
(insn/f 29 28 30 2
  (set (reg:DI 3 bx)
       (mem:DI (post_inc:DI (reg/f:DI 7 sp)) [0  S8 A8]))
   "vartrack-1.c":15 71 {*popdi1}
   (expr_list:REG_CFA_ADJUST_CFA
     (set (reg/f:DI 7 sp)
          (plus:DI (reg/f:DI 7 sp)
                   (const_int 8 [0x8]))) (nil)))
...

However, when we adjust those insns in vartrack to eliminate the pre_dec and
post_inc, the frame location for the push is at argp - 24, while the one for the
pop is at argp - 16:
...
(insn/f 26 3 27 2
  (parallel [
    (set (mem:DI (plus:DI (reg/f:DI 16 argp)
                          (const_int -24 [0xffffffffffffffe8])) [0  S8 A8])
         (reg:DI 3 bx))
    (set (reg/f:DI 7 sp)
         (plus:DI (reg/f:DI 16 argp)
                  (const_int -24 [0xffffffffffffffe8])))
  ])
  "vartrack-1.c":10 61 {*pushdi2_rex64}
  (expr_list:REG_DEAD (reg:DI 3 bx) (nil)))
  ...
(insn/f 29 28 30 2
  (parallel [
    (set (reg:DI 3 bx)
         (mem:DI (plus:DI (reg/f:DI 16 argp)
                          (const_int -16 [0xfffffffffffffff0])) [0  S8 A8]))
    (set (reg/f:DI 7 sp)
         (plus:DI (reg/f:DI 16 argp)
                  (const_int -8 [0xfffffffffffffff8])))
  ])
  "vartrack-1.c":15 71 {*popdi1}
  (expr_list:REG_CFA_ADJUST_CFA
    (set (reg/f:DI 7 sp)
         (plus:DI (reg/f:DI 7 sp)
                  (const_int 8 [0x8]))) (nil)))
...

This patch fixes that by moving the stack_adjust modification after
adjust_insn in vt_initialize.  Also, the patch prints the adjusted insn in a
slim way if dump_flags contain TDF_SLIM, which makes the scan-rtl-dump in the
testcase easier.

Bootstrapped and reg-tested on x86_64.

OK for trunk?

Thanks,
- Tom

[debug] Fix pre_dec handling in vartrack

2018-07-15  Tom de Vries  <tdevries@suse.de>

	* var-tracking.c (vt_initialize): Fix pre_dec handling.  Print adjusted
	insn slim if dump_flags request TDF_SLIM.

	* gcc.target/i386/vartrack-1.c: New test.

---
 gcc/testsuite/gcc.target/i386/vartrack-1.c | 28 ++++++++++++++++++++++++++++
 gcc/var-tracking.c                         | 13 +++++++++++--
 2 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/gcc/testsuite/gcc.target/i386/vartrack-1.c b/gcc/testsuite/gcc.target/i386/vartrack-1.c
new file mode 100644
index 00000000000..15514fc0da7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/vartrack-1.c
@@ -0,0 +1,28 @@
+/* { dg-require-effective-target lp64 } */
+/* { dg-options "-O1 -g -fdump-rtl-vartrack-details-slim" } */
+
+static volatile int vv = 1;
+
+extern long foo (long x);
+
+int
+main ()
+{
+  long x = vv;
+  foo (x);
+  foo (x + 1);
+  return 0;
+}
+
+/* Before adjust_insn:
+   26: [--sp:DI]=bx:DI
+   29: bx:DI=[sp:DI++]
+
+   after adjust_insn:
+   26: {[argp:DI-0x10]=bx:DI;sp:DI=argp:DI-0x10;}
+   29: {bx:DI=[argp:DI-0x10];sp:DI=argp:DI-0x8;} */
+
+/* { dg-final { scan-rtl-dump-times {[0-9][0-9]*: \{\[argp:DI-0x10\]=bx:DI;sp:DI=argp:DI-0x10;\}} 1 "vartrack" } } */
+
+/* { dg-final { scan-rtl-dump-times {[0-9][0-9]*: \{bx:DI=\[argp:DI-0x10\];sp:DI=argp:DI-0x8;\}} 1 "vartrack" } } */
+
diff --git a/gcc/var-tracking.c b/gcc/var-tracking.c
index 8e800960b6d..5058f3cc7d2 100644
--- a/gcc/var-tracking.c
+++ b/gcc/var-tracking.c
@@ -115,6 +115,7 @@
 #include "tree-pretty-print.h"
 #include "rtl-iter.h"
 #include "fibonacci_heap.h"
+#include "print-rtl.h"
 
 typedef fibonacci_heap <long, basic_block_def> bb_heap_t;
 typedef fibonacci_node <long, basic_block_def> bb_heap_node_t;
@@ -10208,12 +10209,17 @@ vt_initialize (void)
 			    log_op_type (PATTERN (insn), bb, insn,
 					 MO_ADJUST, dump_file);
 			  VTI (bb)->mos.safe_push (mo);
-			  VTI (bb)->out.stack_adjust += pre;
 			}
 		    }
 
 		  cselib_hook_called = false;
 		  adjust_insn (bb, insn);
+
+		  if (!frame_pointer_needed)
+		    {
+		      if (pre)
+			VTI (bb)->out.stack_adjust += pre;
+		    }
 		  if (DEBUG_MARKER_INSN_P (insn))
 		    {
 		      reemit_marker_as_note (insn);
@@ -10227,7 +10233,10 @@ vt_initialize (void)
 		      cselib_process_insn (insn);
 		      if (dump_file && (dump_flags & TDF_DETAILS))
 			{
-			  print_rtl_single (dump_file, insn);
+			  if (dump_flags & TDF_SLIM)
+			    dump_insn_slim (dump_file, insn);
+			  else
+			    print_rtl_single (dump_file, insn);
 			  dump_cselib_table (dump_file);
 			}
 		    }