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[PATCH] Fix PR83491
- From: Wilco Dijkstra <Wilco dot Dijkstra at arm dot com>
- To: GCC Patches <gcc-patches at gcc dot gnu dot org>
- Cc: Jakub Jelinek <jakub at redhat dot com>, nd <nd at arm dot com>
- Date: Wed, 20 Dec 2017 13:56:27 +0000
- Subject: [PATCH] Fix PR83491
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This patch fixes PR83491 - if an SSA expression contains 2 identical float
constants, the division reciprocal optimization will ICE. Fix this by explicitly
checking for SSA_NAME in the tree code before walking the uses. Also fix several
coding style issues pointed out by Jakub and make comments more readable.
Bootstrap OK, OK for trunk?
ChangeLog:
2017-12-20 Wilco Dijkstra <wdijkstr@arm.com>
gcc/
PR tree-optimization/83491
* tree-ssa-math-opts.c (execute_cse_reciprocals_1): Check for SSA_NAME
before walking uses. Improve coding style and comments.
gcc/testsuite/
PR tree-optimization/83491
* gcc.dg/pr83491.c: Add new test.
--
diff --git a/gcc/testsuite/gcc.dg/pr83491.c b/gcc/testsuite/gcc.dg/pr83491.c
new file mode 100644
index 0000000000000000000000000000000000000000..f23cc19c72f57ca8d34f05f28fee75fc2c13f33a
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr83491.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O1 -funsafe-math-optimizations" } */
+
+float a;
+float b;
+void bar ()
+{
+ a = __builtin_nanf ("");
+ b = __builtin_powf (a, 2.5F);
+}
diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 8db12f5e1cd5d227bd6c3780420e93cd3fe7b435..4e8f5e728d0c8ef5ac564d8c3c999d8a6ff15e7e 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -544,29 +544,32 @@ execute_cse_reciprocals_1 (gimple_stmt_iterator *def_gsi, tree def)
int square_recip_count = 0;
int sqrt_recip_count = 0;
- gcc_assert (FLOAT_TYPE_P (TREE_TYPE (def)) && is_gimple_reg (def));
+ gcc_assert (FLOAT_TYPE_P (TREE_TYPE (def)) && is_gimple_reg (def)
+ && TREE_CODE (def) == SSA_NAME);
threshold = targetm.min_divisions_for_recip_mul (TYPE_MODE (TREE_TYPE (def)));
- /* If this is a square (x * x), we should check whether there are any
- enough divisions by x on it's own to warrant waiting for that pass. */
- if (TREE_CODE (def) == SSA_NAME)
+ /* If DEF is a square (x * x), count the number of divisions by x.
+ If there are more divisions by x than by (DEF * DEF), prefer to optimize
+ the reciprocal of x instead of DEF. This improves cases like:
+ def = x * x
+ t0 = a / def
+ t1 = b / def
+ t2 = c / x
+ Reciprocal optimization of x results in 1 division rather than 2 or 3. */
+ gimple *def_stmt = SSA_NAME_DEF_STMT (def);
+
+ if (is_gimple_assign (def_stmt)
+ && gimple_assign_rhs_code (def_stmt) == MULT_EXPR
+ && TREE_CODE (gimple_assign_rhs1 (def_stmt)) == SSA_NAME
+ && gimple_assign_rhs1 (def_stmt) == gimple_assign_rhs2 (def_stmt))
{
- gimple *def_stmt = SSA_NAME_DEF_STMT (def);
+ tree op0 = gimple_assign_rhs1 (def_stmt);
- if (is_gimple_assign (def_stmt)
- && gimple_assign_rhs_code (def_stmt) == MULT_EXPR
- && gimple_assign_rhs1 (def_stmt) == gimple_assign_rhs2 (def_stmt))
+ FOR_EACH_IMM_USE_FAST (use_p, use_iter, op0)
{
- /* This statement is a square of something. We should take this
- in to account, as it may be more profitable to not extract
- the reciprocal here. */
- tree op0 = gimple_assign_rhs1 (def_stmt);
- FOR_EACH_IMM_USE_FAST (use_p, use_iter, op0)
- {
- gimple *use_stmt = USE_STMT (use_p);
- if (is_division_by (use_stmt, op0))
- sqrt_recip_count ++;
- }
+ gimple *use_stmt = USE_STMT (use_p);
+ if (is_division_by (use_stmt, op0))
+ sqrt_recip_count++;
}
}
@@ -587,26 +590,23 @@ execute_cse_reciprocals_1 (gimple_stmt_iterator *def_gsi, tree def)
gimple *square_use_stmt = USE_STMT (square_use_p);
if (is_division_by (square_use_stmt, square_def))
{
- /* Halve the relative importance as this is called twice
- for each division by a square. */
+ /* This is executed twice for each division by a square. */
register_division_in (gimple_bb (square_use_stmt), 1);
- square_recip_count ++;
+ square_recip_count++;
}
}
}
}
- /* Square reciprocals will have been counted twice. */
+ /* Square reciprocals were counted twice above. */
square_recip_count /= 2;
+ /* If it is more profitable to optimize 1 / x, don't optimize 1 / (x * x). */
if (sqrt_recip_count > square_recip_count)
- /* It will be more profitable to extract a 1 / x expression later,
- so it is not worth attempting to extract 1 / (x * x) now. */
return;
/* Do the expensive part only if we can hope to optimize something. */
- if (count + square_recip_count >= threshold
- && count >= 1)
+ if (count + square_recip_count >= threshold && count >= 1)
{
gimple *use_stmt;
for (occ = occ_head; occ; occ = occ->next)
@@ -623,8 +623,7 @@ execute_cse_reciprocals_1 (gimple_stmt_iterator *def_gsi, tree def)
FOR_EACH_IMM_USE_ON_STMT (use_p, use_iter)
replace_reciprocal (use_p);
}
- else if (square_recip_count > 0
- && is_square_of (use_stmt, def))
+ else if (square_recip_count > 0 && is_square_of (use_stmt, def))
{
FOR_EACH_IMM_USE_ON_STMT (use_p, use_iter)
{