phiopt: Optimize x < 0 ? ~y : y to (x >> 31) ^ y [PR96928]
As requested in the PR, the one's complement abs can be done more
efficiently without cmov or branching.
Had to change the ifcvt-onecmpl-abs-1.c testcase, we no longer optimize
it in ifcvt, on x86_64 with -m32 we generate in the end the exact same
code, but with -m64:
movl %edi, %eax
- notl %eax
- cmpl %edi, %eax
- cmovl %edi, %eax
+ sarl $31, %eax
+ xorl %edi, %eax
ret
2021-01-05 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/96928
* tree-ssa-phiopt.c (xor_replacement): New function.
(tree_ssa_phiopt_worker): Call it.
* gcc.dg/tree-ssa/pr96928.c: New test.
* gcc.target/i386/ifcvt-onecmpl-abs-1.c: Remove -fdump-rtl-ce1,
instead of scanning rtl dump for ifcvt message check assembly
for xor instruction.
This commit is contained in:
Jakub Jelinek
parent
5ca2400270
commit
576714b309
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@ -0,0 +1,38 @@
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/* PR tree-optimization/96928 */
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/* { dg-do compile } */
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/* { dg-options "-O2 -fdump-tree-phiopt2" } */
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/* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
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/* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
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/* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
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/* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
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/* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
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int
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foo (int a)
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{
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return a < 0 ? ~a : a;
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}
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int
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bar (int a, int b)
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{
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return a < 0 ? ~b : b;
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}
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unsigned
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baz (int a, unsigned int b)
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{
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return a < 0 ? ~b : b;
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}
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unsigned
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qux (int a, unsigned int c)
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{
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return a >= 0 ? ~c : c;
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}
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int
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corge (int a, int b)
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{
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return a >= 0 ? b : ~b;
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}
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@ -1,5 +1,5 @@
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/* { dg-do compile } */
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/* { dg-options "-O2 -fdump-rtl-ce1" } */
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/* { dg-options "-O2" } */
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/* Check code generation for one's complement version of abs */
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@ -10,4 +10,4 @@ int onecmplabs(int x)
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return x;
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}
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/* { dg-final { scan-rtl-dump "succeeded through noce_try_abs" "ce1" } } */
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/* { dg-final { scan-assembler "\txor" } } */
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@ -62,6 +62,8 @@ static bool minmax_replacement (basic_block, basic_block,
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edge, edge, gimple *, tree, tree);
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static bool abs_replacement (basic_block, basic_block,
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edge, edge, gimple *, tree, tree);
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static bool xor_replacement (basic_block, basic_block,
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edge, edge, gimple *, tree, tree);
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static bool cond_removal_in_popcount_clz_ctz_pattern (basic_block, basic_block,
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edge, edge, gimple *,
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tree, tree);
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@ -345,6 +347,9 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
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cfgchanged = true;
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else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
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cfgchanged = true;
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else if (!early_p
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&& xor_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
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cfgchanged = true;
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else if (!early_p
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&& cond_removal_in_popcount_clz_ctz_pattern (bb, bb1, e1,
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e2, phi, arg0,
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@ -2098,6 +2103,109 @@ abs_replacement (basic_block cond_bb, basic_block middle_bb,
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return true;
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}
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/* Optimize x < 0 ? ~y : y into (x >> (prec-1)) ^ y. */
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static bool
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xor_replacement (basic_block cond_bb, basic_block middle_bb,
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edge e0 ATTRIBUTE_UNUSED, edge e1,
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gimple *phi, tree arg0, tree arg1)
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{
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if (!INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
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return false;
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/* OTHER_BLOCK must have only one executable statement which must have the
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form arg0 = ~arg1 or arg1 = ~arg0. */
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gimple *assign = last_and_only_stmt (middle_bb);
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/* If we did not find the proper one's complement assignment, then we cannot
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optimize. */
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if (assign == NULL)
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return false;
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/* If we got here, then we have found the only executable statement
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in OTHER_BLOCK. If it is anything other than arg = ~arg1 or
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arg1 = ~arg0, then we cannot optimize. */
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if (!is_gimple_assign (assign))
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return false;
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if (gimple_assign_rhs_code (assign) != BIT_NOT_EXPR)
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return false;
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tree lhs = gimple_assign_lhs (assign);
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tree rhs = gimple_assign_rhs1 (assign);
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/* The assignment has to be arg0 = -arg1 or arg1 = -arg0. */
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if (!(lhs == arg0 && rhs == arg1) && !(lhs == arg1 && rhs == arg0))
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return false;
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gimple *cond = last_stmt (cond_bb);
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tree result = PHI_RESULT (phi);
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/* Only relationals comparing arg[01] against zero are interesting. */
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enum tree_code cond_code = gimple_cond_code (cond);
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if (cond_code != LT_EXPR && cond_code != GE_EXPR)
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return false;
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/* Make sure the conditional is x OP 0. */
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tree clhs = gimple_cond_lhs (cond);
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if (TREE_CODE (clhs) != SSA_NAME
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|| !INTEGRAL_TYPE_P (TREE_TYPE (clhs))
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|| TYPE_UNSIGNED (TREE_TYPE (clhs))
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|| TYPE_PRECISION (TREE_TYPE (clhs)) != TYPE_PRECISION (TREE_TYPE (arg1))
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|| !integer_zerop (gimple_cond_rhs (cond)))
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return false;
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/* We need to know which is the true edge and which is the false
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edge so that we know if have xor or inverted xor. */
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edge true_edge, false_edge;
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extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
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/* For GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
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will need to invert the result. Similarly for LT_EXPR if
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the false edge goes to OTHER_BLOCK. */
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edge e;
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if (cond_code == GE_EXPR)
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e = true_edge;
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else
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e = false_edge;
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bool invert = e->dest == middle_bb;
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result = duplicate_ssa_name (result, NULL);
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gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
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int prec = TYPE_PRECISION (TREE_TYPE (clhs));
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gimple *new_stmt
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= gimple_build_assign (make_ssa_name (TREE_TYPE (clhs)), RSHIFT_EXPR, clhs,
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build_int_cst (integer_type_node, prec - 1));
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gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
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if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (clhs)))
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{
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new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
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NOP_EXPR, gimple_assign_lhs (new_stmt));
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gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
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}
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lhs = gimple_assign_lhs (new_stmt);
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if (invert)
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{
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new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
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BIT_NOT_EXPR, rhs);
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gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
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rhs = gimple_assign_lhs (new_stmt);
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}
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new_stmt = gimple_build_assign (result, BIT_XOR_EXPR, lhs, rhs);
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gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
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replace_phi_edge_with_variable (cond_bb, e1, phi, result);
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/* Note that we optimized this PHI. */
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return true;
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}
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/* Auxiliary functions to determine the set of memory accesses which
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can't trap because they are preceded by accesses to the same memory
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portion. We do that for MEM_REFs, so we only need to track
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