Hi!
As mentioned in the PR, the code emitted by ix86_expand_rint
doesn't work with rounding to +/- infinity.
This patch adjusts it if flag_rounding_math to do something that works
well even for that case (should be just one insn longer).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2017-12-07 Joseph Myers <jos...@codesourcery.com>
Alexander Monakov <amona...@ispras.ru>
Jakub Jelinek <ja...@redhat.com>
PR target/81906
* config/i386/i386.c (ix86_expand_rint): Handle flag_rounding_math.
* gcc.target/i386/pr81906.c: New test.
--- gcc/config/i386/i386.c.jj 2017-12-05 10:15:31.000000000 +0100
+++ gcc/config/i386/i386.c 2017-12-07 11:58:15.159881741 +0100
@@ -44255,8 +44255,7 @@ ix86_expand_lfloorceil (rtx op0, rtx op1
emit_move_insn (op0, ireg);
}
-/* Expand rint (IEEE round to nearest) rounding OPERAND1 and storing the
- result in OPERAND0. */
+/* Expand rint rounding OPERAND1 and storing the result in OPERAND0. */
void
ix86_expand_rint (rtx operand0, rtx operand1)
{
@@ -44264,11 +44263,17 @@ ix86_expand_rint (rtx operand0, rtx oper
xa = fabs (operand1);
if (!isless (xa, 2**52))
return operand1;
- xa = xa + 2**52 - 2**52;
+ two52 = 2**52;
+ if (flag_rounding_math)
+ {
+ two52 = copysign (two52, operand1);
+ xa = operand1;
+ }
+ xa = xa + two52 - two52;
return copysign (xa, operand1);
*/
machine_mode mode = GET_MODE (operand0);
- rtx res, xa, TWO52, mask;
+ rtx res, xa, TWO52, two52, mask;
rtx_code_label *label;
res = gen_reg_rtx (mode);
@@ -44281,8 +44286,16 @@ ix86_expand_rint (rtx operand0, rtx oper
TWO52 = ix86_gen_TWO52 (mode);
label = ix86_expand_sse_compare_and_jump (UNLE, TWO52, xa, false);
- xa = expand_simple_binop (mode, PLUS, xa, TWO52, NULL_RTX, 0, OPTAB_DIRECT);
- xa = expand_simple_binop (mode, MINUS, xa, TWO52, xa, 0, OPTAB_DIRECT);
+ two52 = TWO52;
+ if (flag_rounding_math)
+ {
+ two52 = gen_reg_rtx (mode);
+ ix86_sse_copysign_to_positive (two52, TWO52, res, mask);
+ xa = res;
+ }
+
+ xa = expand_simple_binop (mode, PLUS, xa, two52, NULL_RTX, 0, OPTAB_DIRECT);
+ xa = expand_simple_binop (mode, MINUS, xa, two52, xa, 0, OPTAB_DIRECT);
ix86_sse_copysign_to_positive (res, xa, res, mask);
--- gcc/testsuite/gcc.target/i386/pr81906.c.jj 2017-12-07 11:38:06.730812658
+0100
+++ gcc/testsuite/gcc.target/i386/pr81906.c 2017-12-07 11:38:14.488716544
+0100
@@ -0,0 +1,37 @@
+/* PR target/81906 */
+/* { dg-do run { target *-*-linux* *-*-gnu* } }
+/* { dg-options "-O2 -frounding-math" } */
+
+#include <fenv.h>
+
+int
+main ()
+{
+ #define N 12
+ double a[N] = { 2.0, 2.25, 2.5, 2.75, 3.5, -2.0, -2.25, -2.5, -2.75, -3.5,
0x2.0p53, -0x2.0p53 };
+ double b[N], c[N], d[N], e[N];
+ double be[N] = { 2.0, 2.0, 2.0, 3.0, 4.0, -2.0, -2.0, -2.0, -3.0, -4.0,
0x2.0p53, -0x2.0p53 };
+ double ce[N] = { 2.0, 2.0, 2.0, 2.0, 3.0, -2.0, -3.0, -3.0, -3.0, -4.0,
0x2.0p53, -0x2.0p53 };
+ double de[N] = { 2.0, 3.0, 3.0, 3.0, 4.0, -2.0, -2.0, -2.0, -2.0, -3.0,
0x2.0p53, -0x2.0p53 };
+ double ee[N] = { 2.0, 2.0, 2.0, 2.0, 3.0, -2.0, -2.0, -2.0, -2.0, -3.0,
0x2.0p53, -0x2.0p53 };
+ asm volatile ("" : : "g" (a), "g" (be), "g" (ce), "g" (de), "g" (ee) :
"memory");
+
+ int i;
+ fesetround (FE_TONEAREST);
+ for (i = 0; i < N; ++i)
+ b[i] = __builtin_rint (a[i]);
+ fesetround (FE_DOWNWARD);
+ for (i = 0; i < N; ++i)
+ c[i] = __builtin_rint (a[i]);
+ fesetround (FE_UPWARD);
+ for (i = 0; i < N; ++i)
+ d[i] = __builtin_rint (a[i]);
+ fesetround (FE_TOWARDZERO);
+ for (i = 0; i < N; ++i)
+ e[i] = __builtin_rint (a[i]);
+ fesetround (FE_TONEAREST);
+ for (i = 0; i < N; ++i)
+ if (b[i] != be[i] || c[i] != ce[i] || d[i] != de[i] || e[i] != ee[i])
+ __builtin_abort ();
+ return 0;
+}
Jakub
