re PR rtl-optimization/13037 ([gcse-lm] g77 generates incorrect code)

PR optimization/13037
	* loop.c (update_giv_derive): Ignore redundant sets of a biv when
	calculating how to derive a giv from a biv.

	* g77.f-torture/execute/13037.f: New test case.

From-SVN: r74572

gcc/ChangeLog

@@ -1,3 +1,9 @@
+2003-12-12  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/13037
+	* loop.c (update_giv_derive): Ignore redundant sets of a biv when
+	calculating how to derive a giv from a biv.
+
 2003-12-12  Neil Booth  <neil@daikokuya.co.uk>
 
 	PR preprocessor/12935 preprocessor/12952 preprocessor/13046

gcc/loop.c

@@ -6095,6 +6095,10 @@ update_giv_derive (const struct loop *loop, rtx p)
       if (GET_CODE (p) == CODE_LABEL || GET_CODE (p) == JUMP_INSN
 	  || biv->insn == p)
 	{
+	  /* Skip if location is the same as a previous one.  */
+	  if (biv->same)
+	    continue;
+
 	  for (giv = bl->giv; giv; giv = giv->next_iv)
 	    {
 	      /* If cant_derive is already true, there is no point in

gcc/testsuite/ChangeLog

@@ -1,3 +1,8 @@
+2003-12-12  Roger Sayle  <roger@eyesopen.com>
+
+	PR optimization/13037
+	* g77.f-torture/execute/13037.f: New test case.
+
 2003-12-12  Nathan Sidwell  <nathan@codesourcery.com>
 
 	PR c++/12881

gcc/testsuite/g77.f-torture/execute/13037.f

@@ -0,0 +1,58 @@
+c      PR optimization/13037
+c      Contributed by Kirill Smelkov
+c      bug symptom: zeta(kkzc) seems to reference to zeta(kkzc-1) instead
+c      with gcc-3.2.2 it is OK, so it is a regression.
+c
+      subroutine bug1(expnt)
+      implicit none
+
+      double precision zeta
+      common /bug1_area/zeta(3)
+
+      double precision expnt(3)
+
+
+      integer k, kkzc
+
+      kkzc=0
+      do k=1,3
+         kkzc = kkzc + 1
+         zeta(kkzc) = expnt(k)
+      enddo
+
+c     the following line activates the bug
+      call bug1_activator(kkzc)
+      end
+
+
+c     dummy subroutine
+      subroutine bug1_activator(inum)
+      implicit none
+      integer inum
+      end
+
+
+c     test driver
+      program test_bug1
+      implicit none
+
+      double precision zeta
+      common /bug1_area/zeta(3)
+
+      double precision expnt(3)
+
+      zeta(1) = 0.0d0
+      zeta(2) = 0.0d0
+      zeta(3) = 0.0d0
+
+      expnt(1) = 1.0d0
+      expnt(2) = 2.0d0
+      expnt(3) = 3.0d0
+
+      call bug1(expnt)
+      if ((zeta(1).ne.1) .or. (zeta(2).ne.2) .or. (zeta(3).ne.3)) then
+        call abort
+      endif
+
+      end
+