On Thu, 21 Jul 2011, Joseph S. Myers wrote:
> On Thu, 21 Jul 2011, Richard Henderson wrote:
>
> > On 07/21/2011 08:09 AM, Richard Guenther wrote:
> > > + /* It's not interesting to widen anything smaller than SImode. */
> > > + if (TYPE_PRECISION (TREE_TYPE (rhs1)) < GET_MODE_PRECISION (SImode)
> > > + || (!TYPE_UNSIGNED (TREE_TYPE (rhs1))
> > > + && TYPE_PRECISION (TREE_TYPE (rhs1)) == GET_MODE_PRECISION
> > > (SImode)))
> > > + return false;
> >
> > Hard-coding SImode? Really? You might as well hard-code 32. At least
> > that's "more correct" when someone does have BITS_PER_UNIT != 8.
>
> I'd guess this is intended to match the hardcoding of SImode in
> optabs.c:expand_float - both of which should maybe use the same target
> hook (that defaults to using SImode) rather than hardcoding SImode.
> (Strictly, in the model that the very existence of SImode should be
> target-dependent, the default hook definition would go in a file in
> config/ that's shared by all targets with BITS_PER_UNIT == 8 and the
> classic set of machine modes, rather than in targhooks.c, but I don't
> think we need to worry about that for now.)
Hm, of course some targets define unsigned float expanders just do
do the complicated stuff manually (which is why I didn't look
at the conversion optabs). I assume that if a target can do
an unsigned -> float conversion it can also to a signed -> float
conversion of the same source mode (probably a safe assumption?).
Patch also handling wider modes and not starting with SImode but
the mode of int:
2011-07-21 Richard Guenther <rguent...@suse.de>
PR tree-optimization/49715
* tree-vrp.c (simplify_float_conversion_using_ranges): New
function.
(simplify_stmt_using_ranges): Call it.
* gcc.target/i386/pr49715-1.c: New testcase.
* gcc.target/i386/pr49715-2.c: Likewise.
Index: gcc/tree-vrp.c
===================================================================
*** gcc/tree-vrp.c.orig 2011-07-21 16:46:39.000000000 +0200
--- gcc/tree-vrp.c 2011-07-21 17:37:09.000000000 +0200
*************** simplify_conversion_using_ranges (gimple
*** 7448,7453 ****
--- 7448,7516 ----
return true;
}
+ /* Simplify a conversion from integral SSA name to float in STMT. */
+
+ static bool
+ simplify_float_conversion_using_ranges (gimple_stmt_iterator *gsi, gimple
stmt)
+ {
+ tree rhs1 = gimple_assign_rhs1 (stmt);
+ value_range_t *vr = get_value_range (rhs1);
+ enum machine_mode mode;
+ tree tem;
+ gimple conv;
+
+ /* It's not interesting to widen anything. */
+ if (TYPE_PRECISION (TREE_TYPE (rhs1)) < TYPE_PRECISION (integer_type_node)
+ || (!TYPE_UNSIGNED (TREE_TYPE (rhs1))
+ && (TYPE_PRECISION (TREE_TYPE (rhs1))
+ == TYPE_PRECISION (integer_type_node))))
+ return false;
+
+ /* We can only handle constant ranges. */
+ if (vr->type != VR_RANGE
+ || TREE_CODE (vr->min) != INTEGER_CST
+ || TREE_CODE (vr->max) != INTEGER_CST)
+ return false;
+
+ /* Search for a mode we can use. Start with that of int. */
+ mode = TYPE_MODE (integer_type_node);
+ do
+ {
+ double_int tem;
+
+ tem = double_int_ext (tree_to_double_int (vr->min),
+ GET_MODE_PRECISION (mode), 0);
+ if (double_int_equal_p (tree_to_double_int (vr->min), tem))
+ {
+ tem = double_int_ext (tree_to_double_int (vr->max),
+ GET_MODE_PRECISION (mode), 0);
+ if (double_int_equal_p (tree_to_double_int (vr->max), tem))
+ break;
+ }
+
+ mode = GET_MODE_WIDER_MODE (mode);
+ if (GET_MODE_PRECISION (mode) > TYPE_PRECISION (TREE_TYPE (rhs1)))
+ return false;
+ }
+ while (mode != VOIDmode);
+
+ if (mode == VOIDmode)
+ return false;
+
+ /* It works, insert a truncation or sign-change before the
+ float conversion. */
+ tem = create_tmp_var (build_nonstandard_integer_type
+ (GET_MODE_PRECISION (mode), 0), NULL);
+ conv = gimple_build_assign_with_ops (NOP_EXPR, tem, rhs1, NULL_TREE);
+ tem = make_ssa_name (tem, conv);
+ gimple_assign_set_lhs (conv, tem);
+ gsi_insert_before (gsi, conv, GSI_SAME_STMT);
+ gimple_assign_set_rhs1 (stmt, tem);
+ update_stmt (stmt);
+
+ return true;
+ }
+
/* Simplify STMT using ranges if possible. */
static bool
*************** simplify_stmt_using_ranges (gimple_stmt_
*** 7507,7512 ****
--- 7570,7581 ----
return simplify_conversion_using_ranges (stmt);
break;
+ case FLOAT_EXPR:
+ if (TREE_CODE (rhs1) == SSA_NAME
+ && INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
+ return simplify_float_conversion_using_ranges (gsi, stmt);
+ break;
+
default:
break;
}
Index: gcc/testsuite/gcc.target/i386/pr49715-1.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.target/i386/pr49715-1.c 2011-07-21 16:55:57.000000000
+0200
***************
*** 0 ****
--- 1,9 ----
+ /* { dg-do compile } */
+ /* { dg-options "-O2 -msse -mfpmath=sse" } */
+
+ float func(unsigned x)
+ {
+ return (x & 0xfffff) * 0.01f;
+ }
+
+ /* { dg-final { scan-assembler-times "cvtsi2ss" 1 } } */
Index: gcc/testsuite/gcc.target/i386/pr49715-2.c
===================================================================
*** /dev/null 1970-01-01 00:00:00.000000000 +0000
--- gcc/testsuite/gcc.target/i386/pr49715-2.c 2011-07-21 17:46:05.000000000
+0200
***************
*** 0 ****
--- 1,12 ----
+ /* { dg-do compile } */
+ /* { dg-require-effective-target lp64 } */
+ /* { dg-options "-O2" } */
+
+ double func(unsigned long long x)
+ {
+ if (x <= 0x7ffffffffffffffeULL)
+ return (x + 1) * 0.01;
+ return 0.0;
+ }
+
+ /* { dg-final { scan-assembler-times "cvtsi2sdq" 1 } } */
