https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77975
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
> Proved that loop 1 iterates 2 times using brute force.
so the question is why that doesn't work for the new form (and this is what we
should fix). Because
static gphi *
get_base_for (struct loop *loop, tree x)
{
...
init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
if (TREE_CODE (next) != SSA_NAME)
return NULL;
Index: gcc/tree-ssa-loop-niter.c
===================================================================
--- gcc/tree-ssa-loop-niter.c (revision 241148)
+++ gcc/tree-ssa-loop-niter.c (working copy)
@@ -2545,13 +2551,11 @@ get_base_for (struct loop *loop, tree x)
init = PHI_ARG_DEF_FROM_EDGE (phi, loop_preheader_edge (loop));
next = PHI_ARG_DEF_FROM_EDGE (phi, loop_latch_edge (loop));
- if (TREE_CODE (next) != SSA_NAME)
- return NULL;
-
if (!is_gimple_min_invariant (init))
return NULL;
- if (chain_of_csts_start (loop, next) != phi)
+ if (TREE_CODE (next) == SSA_NAME
+ && chain_of_csts_start (loop, next) != phi)
return NULL;
return phi;
@@ -2574,6 +2578,8 @@ get_val_for (tree x, tree base)
if (!x)
return base;
+ else if (is_gimple_min_invariant (x))
+ return x;
stmt = SSA_NAME_DEF_STMT (x);
if (gimple_code (stmt) == GIMPLE_PHI)
fixes it. But I think it's not correct as it misses the intermediate stmt
evaluations. Some more refactoring (passing in the PHI def to get_val_for)
is necessary I think.
