This patch implements some of the optimizations discussed in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71026.
Simplify (C / x > 0.0) into x > 0.0. If C is negative the comparison is reversed. Simplify (x * C1) > C2 into x > (C2 / C1). Again, if C1 is negative the comparison is reversed. Both transformations are only done with -funsafe-math-optimizations, the constant is non-zero, and not a NaN. OK for commit? ChangeLog 2017-10-17 Wilco Dijkstra <wdijk...@arm.com> Jackson Woodruff <jackson.woodr...@arm.com> gcc/ PR 71026/tree-optimization * match.pd: Simplify floating point comparisons. gcc/testsuite/ PR 71026/tree-optimization * gcc.dg/associate_comparison_1.c: New test. -- diff --git a/gcc/match.pd b/gcc/match.pd index e58a65af59b44a6b82ed8705f62966c5e6f251ac..cb48f079b4a310272e49cc319a1b3b0ff2023ba4 100644 --- a/gcc/match.pd +++ b/gcc/match.pd @@ -352,6 +352,19 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (rdiv @0 (rdiv:s @1 @2)) (mult (rdiv @0 @1) @2))) +(if (flag_unsafe_math_optimizations) + /* Simplify (C / x op 0.0) to x op 0.0 for C > 0. */ + (for op (lt le gt ge) + neg_op (gt ge lt le) + (simplify + (op (rdiv REAL_CST@0 @1) real_zerop@2) + (switch + (if (real_less (&dconst0, TREE_REAL_CST_PTR (@0))) + (op @1 @2)) + /* For C < 0, use the inverted operator. */ + (if (real_less (TREE_REAL_CST_PTR (@0), &dconst0)) + (neg_op @1 @2)))))) + /* Optimize (X & (-A)) / A where A is a power of 2, to X >> log2(A) */ (for div (trunc_div ceil_div floor_div round_div exact_div) (simplify @@ -3546,6 +3559,20 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT) (rdiv @2 @1)) (rdiv (op @0 @2) @1))) + (for cmp (lt le gt ge) + neg_cmp (gt ge lt le) + /* Simplify (x * C1) cmp C2 -> x cmp (C2 / C1), where C1 != 0. */ + (simplify + (cmp (mult @0 REAL_CST@1) REAL_CST@2) + (with + { tree tem = const_binop (RDIV_EXPR, type, @2, @1); } + (if (tem) + (switch + (if (real_less (&dconst0, TREE_REAL_CST_PTR (@1))) + (cmp @0 { tem; })) + (if (real_less (TREE_REAL_CST_PTR (@1), &dconst0)) + (neg_cmp @0 { tem; }))))))) + /* Simplify sqrt(x) * sqrt(y) -> sqrt(x*y). */ (for root (SQRT CBRT) (simplify diff --git a/gcc/testsuite/gcc.dg/associate_comparison_1.c b/gcc/testsuite/gcc.dg/associate_comparison_1.c new file mode 100644 index 0000000000000000000000000000000000000000..d051f052e13812c91cbd2d559bf2af8fae128ee1 --- /dev/null +++ b/gcc/testsuite/gcc.dg/associate_comparison_1.c @@ -0,0 +1,34 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -funsafe-math-optimizations -fdump-tree-optimized" } */ + +int +cmp_mul_1 (float x) +{ + return x * 3 <= 100; +} + +int +cmp_mul_2 (float x) +{ + return x * -5 > 100; +} + +int +div_cmp_1 (float x, float y) +{ + return x / 3 <= y; +} + +int +div_cmp_2 (float x, float y) +{ + return x / 3 <= 1; +} + +int +inv_cmp (float x) +{ + return 5 / x >= 0; +} + +/* { dg-final { scan-tree-dump-not " / " "optimized" } } */