@@ -11596,45 +11596,53 @@ fold_binary_loc (location_t loc, enum tree_code code, tree type,
C1 is a valid shift constant, and C2 is a power of two, i.e.
a single bit. */
if (TREE_CODE (arg0) == BIT_AND_EXPR
- && TREE_CODE (TREE_OPERAND (arg0, 0)) == RSHIFT_EXPR
- && TREE_CODE (TREE_OPERAND (TREE_OPERAND (arg0, 0), 1))
- == INTEGER_CST
&& integer_pow2p (TREE_OPERAND (arg0, 1))
&& integer_zerop (arg1))
{
- tree itype = TREE_TYPE (arg0);
- tree arg001 = TREE_OPERAND (TREE_OPERAND (arg0, 0), 1);
- prec = TYPE_PRECISION (itype);
-
- /* Check for a valid shift count. */
- if (wi::ltu_p (wi::to_wide (arg001), prec))
+ tree arg00 = TREE_OPERAND (arg0, 0);
+ STRIP_NOPS (arg00);
+ if (TREE_CODE (arg00) == RSHIFT_EXPR
+ && TREE_CODE (TREE_OPERAND (arg00, 1)) == INTEGER_CST)
{
- tree arg01 = TREE_OPERAND (arg0, 1);
- tree arg000 = TREE_OPERAND (TREE_OPERAND (arg0, 0), 0);
- unsigned HOST_WIDE_INT log2 = tree_log2 (arg01);
- /* If (C2 << C1) doesn't overflow, then ((X >> C1) & C2) != 0
- can be rewritten as (X & (C2 << C1)) != 0. */
- if ((log2 + TREE_INT_CST_LOW (arg001)) < prec)
+ tree itype = TREE_TYPE (arg00);
+ tree arg001 = TREE_OPERAND (arg00, 1);
+ prec = TYPE_PRECISION (itype);
+
+ /* Check for a valid shift count. */
+ if (wi::ltu_p (wi::to_wide (arg001), prec))
{
- tem = fold_build2_loc (loc, LSHIFT_EXPR, itype, arg01, arg001);
- tem = fold_build2_loc (loc, BIT_AND_EXPR, itype, arg000, tem);
- return fold_build2_loc (loc, code, type, tem,
- fold_convert_loc (loc, itype, arg1));
- }
- /* Otherwise, for signed (arithmetic) shifts,
- ((X >> C1) & C2) != 0 is rewritten as X < 0, and
- ((X >> C1) & C2) == 0 is rewritten as X >= 0. */
- else if (!TYPE_UNSIGNED (itype))
- return fold_build2_loc (loc, code == EQ_EXPR ? GE_EXPR : LT_EXPR, type,
- arg000, build_int_cst (itype, 0));
- /* Otherwise, of unsigned (logical) shifts,
- ((X >> C1) & C2) != 0 is rewritten as (X,false), and
- ((X >> C1) & C2) == 0 is rewritten as (X,true). */
- else
- return omit_one_operand_loc (loc, type,
+ tree arg01 = TREE_OPERAND (arg0, 1);
+ tree arg000 = TREE_OPERAND (arg00, 0);
+ unsigned HOST_WIDE_INT log2 = tree_log2 (arg01);
+ /* If (C2 << C1) doesn't overflow, then
+ ((X >> C1) & C2) != 0 can be rewritten as
+ (X & (C2 << C1)) != 0. */
+ if ((log2 + TREE_INT_CST_LOW (arg001)) < prec)
+ {
+ tem = fold_build2_loc (loc, LSHIFT_EXPR, itype,
+ arg01, arg001);
+ tem = fold_build2_loc (loc, BIT_AND_EXPR, itype,
+ arg000, tem);
+ return fold_build2_loc (loc, code, type, tem,
+ fold_convert_loc (loc, itype, arg1));
+ }
+ /* Otherwise, for signed (arithmetic) shifts,
+ ((X >> C1) & C2) != 0 is rewritten as X < 0, and
+ ((X >> C1) & C2) == 0 is rewritten as X >= 0. */
+ else if (!TYPE_UNSIGNED (itype))
+ return fold_build2_loc (loc, code == EQ_EXPR ? GE_EXPR
+ : LT_EXPR,
+ type, arg000,
+ build_int_cst (itype, 0));
+ /* Otherwise, of unsigned (logical) shifts,
+ ((X >> C1) & C2) != 0 is rewritten as (X,false), and
+ ((X >> C1) & C2) == 0 is rewritten as (X,true). */
+ else
+ return omit_one_operand_loc (loc, type,
code == EQ_EXPR ? integer_one_node
: integer_zero_node,
arg000);
+ }
}
}
PR tree-optimization/21137 is now an old enhancement request pointing out that an optimization I added back in 2006, to optimize "((x>>31)&64) != 0" as "x < 0", doesn't fire in the presence of unanticipated type conversions. The fix is to call STRIP_NOPS at the appropriate point. I'd considered moving this transformation to match.pd, but it's a lot of complex logic that (I suspect) would be just as ugly in match.pd as it is in fold-const.c. 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? 2020-08-21 Roger Sayle <roger@nextmovesoftware.com> gcc/ChangeLog PR tree-optimization/21137 * gcc/fold-const.c (fold_binary_loc) [NE_EXPR/EQ_EXPR]: Call STRIP_NOPS when checking whether to simplify ((x>>C1)&C2) != 0. gcc/testsuite/ChangeLog PR tree-optimization/21137 * gcc.dg/pr21137.c: New test. Thanks in advance, Roger -- Roger Sayle NextMove Software Cambridge, UK diff --git a/gcc/testsuite/gcc.dg/pr21137.c b/gcc/testsuite/gcc.dg/pr21137.c new file mode 100644 index 0000000..6d73dea --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr21137.c @@ -0,0 +1,20 @@ +/* { dg-do compile } */ +/* { dg-options "-O2 -fdump-tree-optimized" } */ + +void foo(); + +void test5_1(int e) +{ + if ((e >> 31) & 64) + foo(); +} + +typedef int myint; + +void test5_2(myint e) +{ + if ((e >> 31) & 64) + foo(); +} + +/* { dg-final { scan-tree-dump-times " < 0" 2 "optimized" } } */