This patch to match.pd implements several closely related folding
simplifications at the tree-level, that make use of the property
that bit permutation functions, rotate and bswap have inverses.
[1] bswap(X) eq/ne C, for constant C, simplifies to X eq/ne C'
where C'=bswap(C), generalizing the transform in the subject.
[2] bswap(X) eq/ne bswap(Y) simplifies to X eq/ne Y.
[3] lrotate(X,C1) eq/ne C2 simplifies to X eq/ne C3, where
C3 = rrotate(C2,C1), i.e. apply the inverse rotation to C2.
[4] Likewise, rrotate(X,C1) eq/ne C2 simplifies to X eq/ne C3,
where C3 = lrotate(C2,C1).
[5] rotate(X,Z) eq/ne rotate(Y,Z) simplifies to X eq/ne Y, when
the bit-count Z (the same on both sides) has no side-effects.
[6] rotate(X,Y) eq/ne 0 simplifies to X eq/ne 0 if Y has no
side-effects.
[7] Likewise, rotate(X,Y) eq/ne -1 simplifies to X eq/ne -1,
if Y has no side-effects.
This patch has been tested on x86_64-pc-linux-gnu with a "make
bootstrap" and "make -k check" with no new failures.
Ok for mainline?
2010-07-18 Roger Sayle <ro...@nextmovesoftware.com>
gcc/ChangeLog
* match.pd (rotate): Simplify equality/inequality of rotations.
(bswap): Simplify equality/inequality tests of byte swapping.
gcc/testsuite/ChangeLog
* gcc.dg/fold-eqrotate-1.c: New test case.
* gcc.dg/fold-eqbswap-1.c: New test case.
Roger
--
Roger Sayle
NextMove Software
Cambridge, UK
diff --git a/gcc/match.pd b/gcc/match.pd
index beb8d27..aa850bb 100644
--- a/gcc/match.pd
+++ b/gcc/match.pd
@@ -3312,6 +3312,25 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
{ tree rotate_type = TREE_TYPE (@0); }
(convert (rotate (convert:rotate_type @1) @2))))))
+(for cmp (eq ne)
+ (for rotate (lrotate rrotate)
+ invrot (rrotate lrotate)
+ /* (X >>r Y) cmp (Z >>r Y) may simplify to X cmp Y. */
+ (simplify
+ (cmp (rotate @1 @0) (rotate @2 @0))
+ (if (GIMPLE || !TREE_SIDE_EFFECTS (@0))
+ (cmp @1 @2)))
+ /* (X >>r C1) cmp C2 may simplify to X cmp C3. */
+ (simplify
+ (cmp (rotate @0 INTEGER_CST@1) INTEGER_CST@2)
+ (cmp @0 { const_binop (invrot, TREE_TYPE (@0), @2, @1); }))
+ /* (X >>r Y) cmp C where C is 0 or ~0, may simplify to X cmp C. */
+ (simplify
+ (cmp (rotate @0 @1) INTEGER_CST@2)
+ (if ((GIMPLE || !TREE_SIDE_EFFECTS (@1))
+ && (integer_zerop (@2) || integer_all_onesp (@2)))
+ (cmp @0 @2)))))
+
/* Simplifications of conversions. */
/* Basic strip-useless-type-conversions / strip_nops. */
@@ -3622,6 +3641,13 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
(simplify
(bswap (bitop:c (bswap @0) @1))
(bitop @0 (bswap @1))))
+ (for cmp (eq ne)
+ (simplify
+ (cmp (bswap @0) (bswap @1))
+ (cmp @0 @1))
+ (simplify
+ (cmp (bswap @0) INTEGER_CST@1)
+ (cmp @0 (bswap @1))))
/* (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))
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
int test1(int x, int y)
{
#if __SIZEOF_INT__ == 4
return __builtin_bswap32(x) == __builtin_bswap32(y);
#else
return x == y;
#endif
}
int test2(int x, int y)
{
#if __SIZEOF_INT__ == 4
return __builtin_bswap32(x) != __builtin_bswap32(y);
#else
return x != y;
#endif
}
int test3(int x)
{
#if __SIZEOF_INT__ == 4
return __builtin_bswap32(x) == 12345;
#else
return x;
#endif
}
int test4(int x)
{
#if __SIZEOF_INT__ == 4
return __builtin_bswap32(x) != 12345;
#else
return x;
#endif
}
int test1ll(long long x, long long y)
{
#if __SIZEOF_LONG_LONG__ == 8
return __builtin_bswap64(x) == __builtin_bswap64(y);
#else
return x == y;
#endif
}
int test2ll(long long x, long long y)
{
#if __SIZEOF_LONG_LONG__ == 8
return __builtin_bswap64(x) != __builtin_bswap64(y);
#else
return x != y;
#endif
}
int test3ll(long long x)
{
#if __SIZEOF_LONG_LONG__ == 8
return __builtin_bswap64(x) == 12345;
#else
return (int)x;
#endif
}
int test4ll(long long x)
{
#if __SIZEOF_LONG_LONG__ == 8
return __builtin_bswap64(x) != 12345;
#else
return (int)x;
#endif
}
int test1s(short x, short y)
{
#if __SIZEOF_SHORT__ == 2
return __builtin_bswap16(x) == __builtin_bswap16(y);
#else
return x == y;
#endif
}
int test2s(short x, short y)
{
#if __SIZEOF_SHORT__ == 2
return __builtin_bswap16(x) != __builtin_bswap16(y);
#else
return x != y;
#endif
}
int test3s(short x)
{
#if __SIZEOF_SHORT__ == 2
return __builtin_bswap16(x) == 12345;
#else
return (int)x;
#endif
}
int test4s(short x)
{
#if __SIZEOF_SHORT__ == 2
return __builtin_bswap16(x) != 12345;
#else
return (int)x;
#endif
}
/* { dg-final { scan-tree-dump-times "__builtin_bswap" 0 "optimized" } } */
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
int test1(unsigned int x, unsigned int y)
{
#if __SIZEOF_INT__ == 4
unsigned int r1 = (x << 16) | (x >> 16);
unsigned int r2 = (y << 16) | (y >> 16);
return r1 == r2;
#else
return x == y;
#endif
}
int test2(unsigned int x)
{
#if __SIZEOF_INT__ == 4
unsigned int r1 = (x << 16) | (x >> 16);
return r1 == 12345;
#else
return x == 12345;
#endif
}
int test3(unsigned int x)
{
#if __SIZEOF_INT__ == 4
unsigned int r1 = (x << 16) | (x >> 16);
return r1 == 0;
#else
return x == 0;
#endif
}
int test4(unsigned int x)
{
#if __SIZEOF_INT__ == 4
unsigned int r1 = (x << 16) | (x >> 16);
return r1 == ~0;
#else
return x == ~0;
#endif
}
/* { dg-final { scan-tree-dump-times "r>>" 0 "optimized" } } */
