Hello!
We can use ROUNDSP/ROUNDSD in round(a) expansion. Currently, we expand
round(a) as (-O2 -ffast-math):
.LFB0:
.cfi_startproc
movsd .LC1(%rip), %xmm1
movapd %xmm0, %xmm2
movsd .LC0(%rip), %xmm3
andpd %xmm1, %xmm2
ucomisd %xmm2, %xmm3
jbe .L2
addsd .LC2(%rip), %xmm2
andnpd %xmm0, %xmm1
movapd %xmm1, %xmm0
cvttsd2siq %xmm2, %rax
cvtsi2sdq %rax, %xmm2
orpd %xmm2, %xmm0
.L2:
rep
ret
Adding -msse4, we now generate branchless code using roundsd:
.LFB0:
.cfi_startproc
movsd .LC0(%rip), %xmm2
movapd %xmm0, %xmm1
andpd %xmm2, %xmm1
andnpd %xmm0, %xmm2
addsd .LC1(%rip), %xmm1
roundsd $1, %xmm1, %xmm1
orpd %xmm2, %xmm1
movapd %xmm1, %xmm0
ret
The patch also simplifies a couple of checks in related patterns.
2011-08-14 Uros Bizjak <ubiz...@gmail.com>
* config/i386/i386.c (ix86_expand_round_sse4): New function.
* config/i386/i386-protos.h (ix86_expand_round_sse4): New prototype.
* config/i386/i386.md (round<mode>2): Use ix86_expand_round_sse4
for TARGET_ROUND.
(rint<mode>2): Simplify TARGET_ROUND check.
(floor<mode>2): Ditto.
(ceil<mode>2): Ditto.
(btrunc<mode>2): Ditto.
Bootstrapped and regression tested on x86_64-pc-linux-gnu {,-m32},
will be committed to mainline soon.
Uros.
Index: i386.md
===================================================================
--- i386.md (revision 177746)
+++ i386.md (working copy)
@@ -14394,11 +14394,11 @@
if (SSE_FLOAT_MODE_P (<MODE>mode) && TARGET_SSE_MATH
&& !flag_trapping_math)
{
- if (!TARGET_ROUND && optimize_insn_for_size_p ())
- FAIL;
if (TARGET_ROUND)
emit_insn (gen_sse4_1_round<mode>2
(operands[0], operands[1], GEN_INT (ROUND_MXCSR)));
+ else if (optimize_insn_for_size_p ())
+ FAIL;
else
ix86_expand_rint (operand0, operand1);
}
@@ -14431,7 +14431,12 @@
if (SSE_FLOAT_MODE_P (<MODE>mode) && TARGET_SSE_MATH
&& !flag_trapping_math && !flag_rounding_math)
{
- if (TARGET_64BIT || (<MODE>mode != DFmode))
+ if (TARGET_ROUND)
+ {
+ operands[1] = force_reg (<MODE>mode, operands[1]);
+ ix86_expand_round_sse4 (operands[0], operands[1]);
+ }
+ else if (TARGET_64BIT || (<MODE>mode != DFmode))
ix86_expand_round (operands[0], operands[1]);
else
ix86_expand_rounddf_32 (operands[0], operands[1]);
@@ -14663,14 +14668,13 @@
&& !flag_trapping_math)"
{
if (SSE_FLOAT_MODE_P (<MODE>mode) && TARGET_SSE_MATH
- && !flag_trapping_math
- && (TARGET_ROUND || optimize_insn_for_speed_p ()))
+ && !flag_trapping_math)
{
- if (!TARGET_ROUND && optimize_insn_for_size_p ())
- FAIL;
if (TARGET_ROUND)
emit_insn (gen_sse4_1_round<mode>2
(operands[0], operands[1], GEN_INT (ROUND_FLOOR)));
+ else if (optimize_insn_for_size_p ())
+ FAIL;
else if (TARGET_64BIT || (<MODE>mode != DFmode))
ix86_expand_floorceil (operand0, operand1, true);
else
@@ -14922,8 +14926,7 @@
&& !flag_trapping_math)"
{
if (SSE_FLOAT_MODE_P (<MODE>mode) && TARGET_SSE_MATH
- && !flag_trapping_math
- && (TARGET_ROUND || optimize_insn_for_speed_p ()))
+ && !flag_trapping_math)
{
if (TARGET_ROUND)
emit_insn (gen_sse4_1_round<mode>2
@@ -15179,8 +15182,7 @@
&& !flag_trapping_math)"
{
if (SSE_FLOAT_MODE_P (<MODE>mode) && TARGET_SSE_MATH
- && !flag_trapping_math
- && (TARGET_ROUND || optimize_insn_for_speed_p ()))
+ && !flag_trapping_math)
{
if (TARGET_ROUND)
emit_insn (gen_sse4_1_round<mode>2
Index: i386-protos.h
===================================================================
--- i386-protos.h (revision 177746)
+++ i386-protos.h (working copy)
@@ -174,6 +174,7 @@
extern void ix86_expand_rint (rtx, rtx);
extern void ix86_expand_floorceil (rtx, rtx, bool);
extern void ix86_expand_floorceildf_32 (rtx, rtx, bool);
+extern void ix86_expand_round_sse4 (rtx, rtx);
extern void ix86_expand_round (rtx, rtx);
extern void ix86_expand_rounddf_32 (rtx, rtx);
extern void ix86_expand_trunc (rtx, rtx);
Index: i386.c
===================================================================
--- i386.c (revision 177746)
+++ i386.c (working copy)
@@ -32676,6 +32676,40 @@
emit_move_insn (operand0, res);
}
+
+/* Expand SSE sequence for computing round
+ from OP1 storing into OP0 using sse4 round insn. */
+void
+ix86_expand_round_sse4 (rtx op0, rtx op1)
+{
+ enum machine_mode mode = GET_MODE (op0);
+ rtx e1, e2, e3, res, half, mask;
+
+ half = CONST_DOUBLE_FROM_REAL_VALUE (dconsthalf, mode);
+
+ /* round(a) = sgn(a) * floor(fabs(a) + 0.5) */
+
+ /* e1 = fabs(op1) */
+ e1 = ix86_expand_sse_fabs (op1, &mask);
+
+ /* e2 = e1 + 0.5 */
+ half = force_reg (mode, half);
+ e2 = expand_simple_binop (mode, PLUS, e1, half, NULL_RTX, 0, OPTAB_DIRECT);
+
+ /* e3 = floor(e2) */
+ e3 = gen_reg_rtx (mode);
+ emit_insn
+ (gen_rtx_SET (VOIDmode, e3,
+ gen_rtx_UNSPEC (mode,
+ gen_rtvec (2, e2, GEN_INT (ROUND_FLOOR)),
+ UNSPEC_ROUND)));
+
+ /* res = copysign (e3, op1) */
+ res = gen_reg_rtx (mode);
+ ix86_sse_copysign_to_positive (res, e3, op1, mask);
+
+ emit_move_insn (op0, res);
+}
/* Table of valid machine attributes. */
