From patchwork Wed Jun 30 09:15:35 2010
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Subject: Fix PR39799: missing uninitialized vars warning
Date: Tue, 29 Jun 2010 23:15:35 -0000
From: Bernd Schmidt <bernds@codesourcery.com>
X-Patchwork-Id: 57388
Message-Id: <4C2B0B37.70209@codesourcery.com>
To: GCC Patches <gcc-patches@gcc.gnu.org>

This is a problem that was introduced with the fix for PR31081.  Looking
at that PR's history, it seems the inliner has problems with overlapping
lifetimes for things where SSA_NAME_OCCURS_IN_ABNORMAL_PHI.

The solution was to zero-initialize all uninitialized variables when
inlining.  This disables warnings for them, which is the regression in
PR39799.

I've bootstrapped and regression tested the patch below on i686-linux.
This limits the zero-initialization to variables with
SSA_NAME_OCCURS_IN_ABNORMAL_PHI.  I doubt register pressure is an issue
since we have another rtl-based init-regs pass.  Ok?


Bernd
PR tree-optimization/39799
	* tree-inline.c (remap_ssa_name): Initialize variable only if
	SSA_NAME_OCCURS_IN_ABNORMAL_PHI.

	PR tree-optimization/39799
	* gcc.dg/uninit-17.c: New test.


Index: tree-inline.c
===================================================================
--- tree-inline.c	(revision 161371)
+++ tree-inline.c	(working copy)
@@ -234,6 +234,7 @@ remap_ssa_name (tree name, copy_body_dat
 	     regions of the CFG, but this is expensive to test.  */
 	  if (id->entry_bb
 	      && is_gimple_reg (SSA_NAME_VAR (name))
+	      && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (name)
 	      && TREE_CODE (SSA_NAME_VAR (name)) != PARM_DECL
 	      && (id->entry_bb != EDGE_SUCC (ENTRY_BLOCK_PTR, 0)->dest
 		  || EDGE_COUNT (id->entry_bb->preds) != 1))
Index: testsuite/gcc.dg/uninit-17.c
===================================================================
--- testsuite/gcc.dg/uninit-17.c	(revision 0)
+++ testsuite/gcc.dg/uninit-17.c	(revision 0)
@@ -0,0 +1,26 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -Wuninitialized" } */
+
+inline int foo(int x)
+{
+  return x;
+}
+static void bar(int a, int *ptr)
+{
+  do
+  {
+    int b;
+    if (b < 40) {
+      ptr[0] = b; /* { dg-warning "may be used uninitialized" } */
+    }
+    b += 1;
+    ptr++;
+  }
+  while (--a != 0);
+}
+void foobar(int a, int *ptr)
+{
+  bar(foo(a), ptr);
+}
+
+/* { dg-message "note: '\[^\n'\]*' was declared here" "note: expected" { target *-*-* } 0 } */