Hi!
These builtins are perfect candidates for bitwise ccp, the bytes are
preserved, just byte-swapped.
Noticed this while wondering why we haven't optimized the f9 function
in another PR, bswap64 zero extended from 32-bits, later casted to 32-bit
unsigned int is 0.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for GCC10?
2019-02-23 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/89475
* tree-ssa-ccp.c (evaluate_stmt): Handle BUILT_IN_BSWAP{16,32,64}
calls.
* gcc.dg/tree-ssa/pr89475.c: New test.
--- gcc/tree-ssa-ccp.c.jj 2019-01-01 12:37:17.078976247 +0100
+++ gcc/tree-ssa-ccp.c 2019-02-23 22:35:23.888343273 +0100
@@ -1960,6 +1960,35 @@ evaluate_stmt (gimple *stmt)
break;
}
+ case BUILT_IN_BSWAP16:
+ case BUILT_IN_BSWAP32:
+ case BUILT_IN_BSWAP64:
+ val = get_value_for_expr (gimple_call_arg (stmt, 0), true);
+ if (val.lattice_val == UNDEFINED)
+ break;
+ else if (val.lattice_val == CONSTANT
+ && val.value
+ && TREE_CODE (val.value) == INTEGER_CST)
+ {
+ tree type = TREE_TYPE (gimple_call_lhs (stmt));
+ int prec = TYPE_PRECISION (type);
+ wide_int wval = wi::to_wide (val.value);
+ val.value
+ = wide_int_to_tree (type,
+ wide_int::from (wval, prec,
+ UNSIGNED).bswap ());
+ val.mask
+ = widest_int::from (wide_int::from (val.mask, prec,
+ UNSIGNED).bswap (),
+ UNSIGNED);
+ if (wi::sext (val.mask, prec) != -1)
+ break;
+ }
+ val.lattice_val = VARYING;
+ val.value = NULL_TREE;
+ val.mask = -1;
+ break;
+
default:;
}
}
--- gcc/testsuite/gcc.dg/tree-ssa/pr89475.c.jj 2019-02-23 18:58:23.035845645
+0100
+++ gcc/testsuite/gcc.dg/tree-ssa/pr89475.c 2019-02-23 18:59:38.462607598
+0100
@@ -0,0 +1,104 @@
+/* PR tree-optimization/89475 */
+/* { dg-do compile { target { ilp32 || lp64 } } } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-not "link_error " "optimized" } } */
+
+void link_error (void);
+
+unsigned short
+f0 (unsigned short x)
+{
+ x &= 0xaa55;
+ x = __builtin_bswap16 (x);
+ if (x & 0xaa55)
+ link_error ();
+ return x;
+}
+
+unsigned short
+f1 (unsigned short x)
+{
+ x &= 0x55aa;
+ x = __builtin_bswap16 (x);
+ if (x & 0x55aa)
+ link_error ();
+ return x;
+}
+
+unsigned int
+f2 (unsigned int x)
+{
+ x &= 0x55aa5aa5U;
+ x = __builtin_bswap32 (x);
+ if (x & 0x5aa555aaU)
+ link_error ();
+ return x;
+}
+
+unsigned long long int
+f3 (unsigned long long int x)
+{
+ x &= 0x55aa5aa544cc2211ULL;
+ x = __builtin_bswap64 (x);
+ if (x & 0xeedd33bb5aa555aaULL)
+ link_error ();
+ return x;
+}
+
+unsigned short
+f4 (unsigned short x)
+{
+ x = __builtin_bswap32 (x);
+ if (x != 0)
+ link_error ();
+ return x;
+}
+
+unsigned int
+f5 (unsigned int x)
+{
+ x = __builtin_bswap64 (x);
+ if (x != 0)
+ link_error ();
+ return x;
+}
+
+unsigned short
+f6 (unsigned short x)
+{
+ x |= 0xaa55;
+ x = __builtin_bswap16 (x);
+ if ((x | 0xaa55) != 0xffff)
+ link_error ();
+ return x;
+}
+
+unsigned short
+f7 (unsigned short x)
+{
+ x |= 0x55aa;
+ x = __builtin_bswap16 (x);
+ if ((x | 0x55aa) != 0xffff)
+ link_error ();
+ return x;
+}
+
+unsigned int
+f8 (unsigned int x)
+{
+ x |= 0x55aa5aa5U;
+ x = __builtin_bswap32 (x);
+ if ((x | 0x5aa555aaU) != 0xffffffffU)
+ link_error ();
+ return x;
+}
+
+unsigned long long int
+f9 (unsigned long long int x)
+{
+ x |= 0x55aa5aa544cc2211ULL;
+ x = __builtin_bswap64 (x);
+ if ((x | 0xeedd33bb5aa555aaULL) != 0xffffffffffffffffULL)
+ link_error ();
+ return x;
+}
Jakub
