flow.c (init_propagate_block_info): Don't consider unchanging memories for dead frame...

        * flow.c (init_propagate_block_info): Don't consider unchanging
        memories for dead frame store elimination.

From-SVN: r39222

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 602dd5fa7e42be42afeb95c1f9e5914c0b911fc0..a1ca492a17c63e831cd7fda5cb43cdf173cea167 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2001-01-23  Richard Henderson  <rth@redhat.com>
+
+       * flow.c (init_propagate_block_info): Don't consider unchanging
+       memories for dead frame store elimination.
+
 2001-01-23  Richard Henderson  <rth@redhat.com>
 
        * varasm.c (UNIQUE_SECTION): Move default implementation ...

diff --git a/gcc/flow.c b/gcc/flow.c
index 2e76e3d398fa7c49861d69e1528eb20e93f9ebfe..00529d9d5e8ca1730cbb45d81be56f9ebbdcee6e 100644 (file)
--- a/gcc/flow.c
+++ b/gcc/flow.c
@@ -4100,6 +4100,13 @@ init_propagate_block_info (bb, live, local_set, cond_local_set, flags)
          {
            rtx mem = SET_DEST (PATTERN (insn));
 
+           /* This optimization is performed by faking a store to the
+              memory at the end of the block.  This doesn't work for
+              unchanging memories because multiple stores to unchanging
+              memory is illegal and alias analysis doesn't consider it.  */
+           if (RTX_UNCHANGING_P (mem))
+             continue;
+
            if (XEXP (mem, 0) == frame_pointer_rtx
                || (GET_CODE (XEXP (mem, 0)) == PLUS
                    && XEXP (XEXP (mem, 0), 0) == frame_pointer_rtx