PR 52573

[Jeff Law <law at redhat dot com>]

I'm approving Bernd's patch referenced here:

http://gcc.gnu.org/ml/gcc-patches/2012-07/msg00421.html

I've added a comment why we're ignoring the REG_DEAD notes for this 
particular case with a pointer back to the PR.  I've also added a test 
to the testsuite.


A prior discussion can be found here:

http://gcc.gnu.org/ml/gcc/2012-03/msg00167.html

Final patch is attached for historical purposes.

Bootstrapped and regression tested on x86_64-linux-gnu.  Also tested the 
new test on m68k before/after this change to verify that it failed 
before and passed after.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 773f4d7..e179e29 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2013-01-18  Bernd Schmidt  <bernds@codesourcery.com>
+
+	PR rtl-optimization/52573
+	* regrename.c (build_def_use): Ignore REG_DEAD notes if there is a
+	REG_UNUSED for the same register.
+
+
 2013-01-17  Richard Biener  <rguenther@suse.de>
 	    Marek Polacek  <polacek@redhat.com>
 
diff --git a/gcc/regrename.c b/gcc/regrename.c
index df3d341..20e2ae9 100644
--- a/gcc/regrename.c
+++ b/gcc/regrename.c
@@ -1710,9 +1710,16 @@ build_def_use (basic_block bb)
 	      scan_rtx (insn, &XEXP (note, 0), ALL_REGS, mark_read,
 			OP_INOUT);
 
-	  /* Step 4: Close chains for registers that die here.  */
+	  /* Step 4: Close chains for registers that die here, unless
+	     the register is mentioned in a REG_UNUSED note.  In that
+	     case we keep the chain open until step #7 below to ensure
+	     it conflicts with other output operands of this insn.
+	     See PR 52573.  Arguably the insn should not have both
+	     notes; it has proven difficult to fix that without
+	     other undesirable side effects.  */
 	  for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
-	    if (REG_NOTE_KIND (note) == REG_DEAD)
+	    if (REG_NOTE_KIND (note) == REG_DEAD
+		&& !find_regno_note (insn, REG_UNUSED, REGNO (XEXP (note, 0))))
 	      {
 		remove_from_hard_reg_set (&live_hard_regs,
 					  GET_MODE (XEXP (note, 0)),
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 21d0f05..cf1890a 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2013-01-17  Jeff Law  <law@redhat.com>
+
+	PR rtl-optimization/52573
+	* gcc.dg/pr52573.c: New test.
 2013-01-17  Jack Howarth <howarth@bromo.med.uc.edu>
 
         PR sanitizer/55679
diff --git a/gcc/testsuite/gcc.dg/pr52573.c b/gcc/testsuite/gcc.dg/pr52573.c
new file mode 100644
index 0000000..7e82749
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr52573.c
@@ -0,0 +1,158 @@
+
+/* { dg-do compile { target  { m68k-*-* } } } */
+/* { dg-options "-w -O3 -funroll-loops" } */
+/* { dg-final { scan-assembler-not "%d0:%d0" } } */
+/* { dg-final { scan-assembler-not "%d1:%d1" } } */
+/* { dg-final { scan-assembler-not "%d2:%d2" } } */
+/* { dg-final { scan-assembler-not "%d3:%d3" } } */
+/* { dg-final { scan-assembler-not "%d4:%d4" } } */
+/* { dg-final { scan-assembler-not "%d5:%d5" } } */
+/* { dg-final { scan-assembler-not "%d6:%d6" } } */
+/* { dg-final { scan-assembler-not "%d7:%d7" } } */
+/* Test arithmetics on bitfields.  */
+
+extern void abort (void);
+extern void exit (int);
+
+unsigned int
+myrnd (void)
+{
+  static unsigned int s = 1388815473;
+  s *= 1103515245;
+  s += 12345;
+  return (s / 65536) % 2048;
+}
+
+#define T(S)					\
+struct S s##S;					\
+struct S retme##S (struct S x)			\
+{						\
+  return x;					\
+}						\
+						\
+unsigned int fn1##S (unsigned int x)		\
+{						\
+  struct S y = s##S;				\
+  y.k += x;					\
+  y = retme##S (y);				\
+  return y.k;					\
+}						\
+						\
+unsigned int fn2##S (unsigned int x)		\
+{						\
+  struct S y = s##S;				\
+  y.k += x;					\
+  y.k %= 15;					\
+  return y.k;					\
+}						\
+						\
+unsigned int retit##S (void)			\
+{						\
+  return s##S.k;				\
+}						\
+						\
+unsigned int fn3##S (unsigned int x)		\
+{						\
+  s##S.k += x;					\
+  return retit##S ();				\
+}						\
+						\
+void test##S (void)				\
+{						\
+  int i;					\
+  unsigned int mask, v, a, r;			\
+  struct S x;					\
+  char *p = (char *) &s##S;			\
+  for (i = 0; i < sizeof (s##S); ++i)		\
+    *p++ = myrnd ();				\
+  if (__builtin_classify_type (s##S.l) == 8)	\
+    s##S.l = 5.25;				\
+  s##S.k = -1;					\
+  mask = s##S.k;				\
+  v = myrnd ();					\
+  a = myrnd ();					\
+  s##S.k = v;					\
+  x = s##S;					\
+  r = fn1##S (a);				\
+  if (x.i != s##S.i || x.j != s##S.j		\
+      || x.k != s##S.k || x.l != s##S.l		\
+      || ((v + a) & mask) != r)			\
+    abort ();					\
+  v = myrnd ();					\
+  a = myrnd ();					\
+  s##S.k = v;					\
+  x = s##S;					\
+  r = fn2##S (a);				\
+  if (x.i != s##S.i || x.j != s##S.j		\
+      || x.k != s##S.k || x.l != s##S.l		\
+      || ((((v + a) & mask) % 15) & mask) != r)	\
+    abort ();					\
+  v = myrnd ();					\
+  a = myrnd ();					\
+  s##S.k = v;					\
+  x = s##S;					\
+  r = fn3##S (a);				\
+  if (x.i != s##S.i || x.j != s##S.j		\
+      || s##S.k != r || x.l != s##S.l		\
+      || ((v + a) & mask) != r)			\
+    abort ();					\
+}
+
+struct A { unsigned int i : 6, l : 1, j : 10, k : 15; }; T(A)
+struct B { unsigned int i : 6, j : 11, k : 15; unsigned int l; }; T(B)
+struct C { unsigned int l; unsigned int i : 6, j : 11, k : 15; }; T(C)
+struct D { unsigned long long l : 6, i : 6, j : 23, k : 29; }; T(D)
+struct E { unsigned long long l, i : 12, j : 23, k : 29; }; T(E)
+struct F { unsigned long long i : 12, j : 23, k : 29, l; }; T(F)
+struct G { unsigned int i : 12, j : 13, k : 7; unsigned long long l; }; T(G)
+struct H { unsigned int i : 12, j : 11, k : 9; unsigned long long l; }; T(H)
+struct I { unsigned short i : 1, j : 6, k : 9; unsigned long long l; }; T(I)
+struct J { unsigned short i : 1, j : 8, k : 7; unsigned short l; }; T(J)
+struct K { unsigned int k : 6, l : 1, j : 10, i : 15; }; T(K)
+struct L { unsigned int k : 6, j : 11, i : 15; unsigned int l; }; T(L)
+struct M { unsigned int l; unsigned int k : 6, j : 11, i : 15; }; T(M)
+struct N { unsigned long long l : 6, k : 6, j : 23, i : 29; }; T(N)
+struct O { unsigned long long l, k : 12, j : 23, i : 29; }; T(O)
+struct P { unsigned long long k : 12, j : 23, i : 29, l; }; T(P)
+struct Q { unsigned int k : 12, j : 13, i : 7; unsigned long long l; }; T(Q)
+struct R { unsigned int k : 12, j : 11, i : 9; unsigned long long l; }; T(R)
+struct S { unsigned short k : 1, j : 6, i : 9; unsigned long long l; }; T(S)
+struct T { unsigned short k : 1, j : 8, i : 7; unsigned short l; }; T(T)
+struct U { unsigned short j : 6, k : 1, i : 9; unsigned long long l; }; T(U)
+struct V { unsigned short j : 8, k : 1, i : 7; unsigned short l; }; T(V)
+struct W { long double l; unsigned int k : 12, j : 13, i : 7; }; T(W)
+struct X { unsigned int k : 12, j : 13, i : 7; long double l; }; T(X)
+struct Y { unsigned int k : 12, j : 11, i : 9; long double l; }; T(Y)
+struct Z { long double l; unsigned int j : 13, i : 7, k : 12; }; T(Z)
+
+int
+main (void)
+{
+  testA ();
+  testB ();
+  testC ();
+  testD ();
+  testE ();
+  testF ();
+  testG ();
+  testH ();
+  testI ();
+  testJ ();
+  testK ();
+  testL ();
+  testM ();
+  testN ();
+  testO ();
+  testP ();
+  testQ ();
+  testR ();
+  testS ();
+  testT ();
+  testU ();
+  testV ();
+  testW ();
+  testX ();
+  testY ();
+  testZ ();
+  exit (0);
+}