Hi!
The following patch avoids infinite recursion during generic folding.
The (cmp (bswap @0) INTEGER_CST@1) simplification relies on
(bswap @1) actually being simplified, if it is not simplified, we just
move the bswap from one operand to the other and if @0 is also INTEGER_CST,
we apply the same rule next.
The reason why bswap @1 isn't folded to INTEGER_CST is that the INTEGER_CST
has TREE_OVERFLOW set on it and fold-const-call.cc predicate punts in
such cases:
static inline bool
integer_cst_p (tree t)
{
return TREE_CODE (t) == INTEGER_CST && !TREE_OVERFLOW (t);
}
The patch uses ! modifier to ensure the bswap is simplified, but because
! is only supported in gimple-match, guards it also with #if GIMPLE.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2022-02-22 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/104644
* match.pd (cmp (bswap @0) INTEGER_CST@1): Restrict optimization to
GIMPLE only and use ! modifier on bswap.
* gcc.dg/pr104644.c: New test.
--- gcc/match.pd.jj 2022-02-18 12:38:06.075393091 +0100
+++ gcc/match.pd 2022-02-22 20:22:02.222022022 +0100
@@ -3959,10 +3959,13 @@ (define_operator_list SYNC_FETCH_AND_AND
(cmp (bswap@2 @0) (bswap @1))
(with { tree ctype = TREE_TYPE (@2); }
(cmp (convert:ctype @0) (convert:ctype @1))))
+#if GIMPLE
(simplify
(cmp (bswap @0) INTEGER_CST@1)
(with { tree ctype = TREE_TYPE (@1); }
- (cmp (convert:ctype @0) (bswap @1)))))
+ (cmp (convert:ctype @0) (bswap! @1))))
+#endif
+ )
/* (bswap(x) >> C1) & C2 can sometimes be simplified to (x >> C3) & C2. */
(simplify
(bit_and (convert1? (rshift@0 (convert2? (bswap@4 @1)) INTEGER_CST@2))
--- gcc/testsuite/gcc.dg/pr104644.c.jj 2022-02-22 20:02:32.020408468 +0100
+++ gcc/testsuite/gcc.dg/pr104644.c 2022-02-22 20:02:04.609785996 +0100
@@ -0,0 +1,9 @@
+/* PR tree-optimization/104644 */
+/* { dg-do compile } */
+/* { dg-options "-Wno-overflow" } */
+
+int
+foo (void)
+{
+ return __builtin_bswap16 (1.31072e+5f) != (signed char) 1.31072e+5f;
+}
Jakub
