https://gcc.gnu.org/g:add4bb94459d6cecae11de279b49f9c1acb14394
commit r15-5022-gadd4bb94459d6cecae11de279b49f9c1acb14394
Author: Andrew Pinski <quic_apin...@quicinc.com>
Date: Fri Nov 1 23:12:52 2024 -0700
VN: Handle `(A CMP B) !=/== 0` for predicates [PR117414]
After the last patch, we also want to record `(A CMP B) != 0`
as `(A CMP B)` and `(A CMP B) == 0` as `(A CMP B)` with the
true/false edges swapped.
This shows up more due to the new handling of
`(A | B) ==/!= 0` in insert_predicates_for_cond
as now we can notice these comparisons which were not seen before.
This is enough to fix the original issue in `gcc.dg/tree-ssa/pr111456-1.c`
and make sure we don't regress it when enhancing ifcombine.
This adds that predicate and allows us to optimize f
in fre-predicated-3.c.
Changes since v1:
* v2: Use vn_valueize.
Bootstrapped and tested on x86_64-linux-gnu.
PR tree-optimization/117414
gcc/ChangeLog:
* tree-ssa-sccvn.cc (insert_predicates_for_cond): Handle `(A CMP B)
!=/== 0`.
gcc/testsuite/ChangeLog:
* gcc.dg/tree-ssa/fre-predicated-3.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
Diff:
---
gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c | 46 ++++++++++++++++++++++++
gcc/tree-ssa-sccvn.cc | 14 ++++++++
2 files changed, 60 insertions(+)
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
new file mode 100644
index 000000000000..4a89372fd703
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/fre-predicated-3.c
@@ -0,0 +1,46 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+/* PR tree-optimization/117414 */
+
+/* Fre1 should figure out that `*aaa != 0`
+ For f0, f1, and f2. */
+
+void foo();
+int f(int *aaa, int j, int t)
+{
+ int b = *aaa;
+ int c = b == 0;
+ int d = t != 1;
+ if (c | d)
+ return 0;
+
+ for(int i = 0; i < j; i++)
+ {
+ if (*aaa)
+ ;
+ else
+ foo();
+ }
+ return 0;
+}
+
+int f1(int *aaa, int j, int t)
+{
+ int b = *aaa;
+ if (b == 0)
+ return 0;
+ if (t != 1)
+ return 0;
+ for(int i = 0; i < j; i++)
+ {
+ if (*aaa)
+ ;
+ else
+ foo();
+ }
+ return 0;
+}
+
+/* { dg-final { scan-tree-dump-not "foo " "optimized" } } */
+/* { dg-final { scan-tree-dump "return 0;" "optimized" } } */
diff --git a/gcc/tree-ssa-sccvn.cc b/gcc/tree-ssa-sccvn.cc
index c6dddd0ba6d7..67ed2cd8ffe1 100644
--- a/gcc/tree-ssa-sccvn.cc
+++ b/gcc/tree-ssa-sccvn.cc
@@ -7948,6 +7948,20 @@ insert_predicates_for_cond (tree_code code, tree lhs,
tree rhs,
&& (code == NE_EXPR || code == EQ_EXPR))
{
gimple *def_stmt = SSA_NAME_DEF_STMT (lhs);
+ /* (A CMP B) != 0 is the same as (A CMP B).
+ (A CMP B) == 0 is just (A CMP B) with the edges swapped. */
+ if (is_gimple_assign (def_stmt)
+ && TREE_CODE_CLASS (gimple_assign_rhs_code (def_stmt)) ==
tcc_comparison)
+ {
+ tree_code nc = gimple_assign_rhs_code (def_stmt);
+ tree nlhs = vn_valueize (gimple_assign_rhs1 (def_stmt));
+ tree nrhs = vn_valueize (gimple_assign_rhs2 (def_stmt));
+ edge nt = true_e;
+ edge nf = false_e;
+ if (code == EQ_EXPR)
+ std::swap (nt, nf);
+ insert_predicates_for_cond (nc, nlhs, nrhs, nt, nf);
+ }
/* (a | b) == 0 ->
on true edge assert: a == 0 & b == 0. */
/* (a | b) != 0 ->
