ifcvt: Fix -fcompare-debug bug [PR100852]

Message ID 20210609081910.GU7746@tucnak
State New
Headers show
Series
  • ifcvt: Fix -fcompare-debug bug [PR100852]
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Commit Message

H.J. Lu via Gcc-patches June 9, 2021, 8:19 a.m.
Hi!

The following testcase fails -fcompare-debug, because it is ifcvt optimized
into umin only with -g0 and not with -g - the function(s) use
prev_nonnote_insn, which without -g finds a real insn the code is looking
for, while with -g finds a DEBUG_INSN.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2021-06-09  Jakub Jelinek  <jakub@redhat.com>

	PR debug/100852
	* ifcvt.c (noce_get_alt_condition, noce_try_abs): Use
	prev_nonnote_nondebug_insn instead of prev_nonnote_insn.

	* g++.dg/opt/pr100852.C: New test.


	Jakub

Comments

Eric Botcazou June 9, 2021, 9:57 a.m. | #1
> The following testcase fails -fcompare-debug, because it is ifcvt optimized

> into umin only with -g0 and not with -g - the function(s) use

> prev_nonnote_insn, which without -g finds a real insn the code is looking

> for, while with -g finds a DEBUG_INSN.

> 

> Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for

> trunk?

> 

> 2021-06-09  Jakub Jelinek  <jakub@redhat.com>

> 

> 	PR debug/100852

> 	* ifcvt.c (noce_get_alt_condition, noce_try_abs): Use

> 	prev_nonnote_nondebug_insn instead of prev_nonnote_insn.

> 

> 	* g++.dg/opt/pr100852.C: New test.


This looks obvious to me, but OK.

-- 
Eric Botcazou

Patch

--- gcc/ifcvt.c.jj	2021-05-04 21:02:24.061801088 +0200
+++ gcc/ifcvt.c	2021-06-08 15:36:53.339411347 +0200
@@ -2398,7 +2398,7 @@  noce_get_alt_condition (struct noce_if_i
       rtx_insn *prev_insn;
 
       /* First, look to see if we put a constant in a register.  */
-      prev_insn = prev_nonnote_insn (if_info->cond_earliest);
+      prev_insn = prev_nonnote_nondebug_insn (if_info->cond_earliest);
       if (prev_insn
 	  && BLOCK_FOR_INSN (prev_insn)
 	     == BLOCK_FOR_INSN (if_info->cond_earliest)
@@ -2669,7 +2669,7 @@  noce_try_abs (struct noce_if_info *if_in
   if (REG_P (c))
     {
       rtx set;
-      rtx_insn *insn = prev_nonnote_insn (earliest);
+      rtx_insn *insn = prev_nonnote_nondebug_insn (earliest);
       if (insn
 	  && BLOCK_FOR_INSN (insn) == BLOCK_FOR_INSN (earliest)
 	  && (set = single_set (insn))
--- gcc/testsuite/g++.dg/opt/pr100852.C.jj	2021-06-08 15:39:48.089013415 +0200
+++ gcc/testsuite/g++.dg/opt/pr100852.C	2021-06-08 15:41:12.816850768 +0200
@@ -0,0 +1,25 @@ 
+// PR debug/100852
+// { dg-do compile }
+// { dg-options "-Og -fif-conversion -fno-tree-ccp -fno-tree-copy-prop -fcompare-debug" }
+
+static inline int
+min (unsigned a, int b)
+{
+  return a < b ? a : b;
+}
+
+struct S { S (char); };
+
+static inline S
+foo (unsigned x)
+{
+  int h;
+  h += min (x * 4, h);
+  return h;
+}
+
+void
+bar ()
+{
+  foo (0);
+}