Bootstrapped and tested on x86_64-linux-gnu, OK for trunk?
gcc/ChangeLog:
* config/i386/i386.md: Rewrite insn truncsfbf2.
gcc/testsuite/ChangeLog:
* gcc.target/i386/truncsfbf-1.c: New test.
* gcc.target/i386/truncsfbf-2.c: New test.
---
gcc/config/i386/i386.md | 16 ++---
gcc/testsuite/gcc.target/i386/truncsfbf-1.c | 9 +++
gcc/testsuite/gcc.target/i386/truncsfbf-2.c | 65 +++++++++++++++++++++
3 files changed, 83 insertions(+), 7 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/i386/truncsfbf-1.c
create mode 100644 gcc/testsuite/gcc.target/i386/truncsfbf-2.c
diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index 9c2a0aa6112..d3fee0968d8 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -5672,16 +5672,18 @@
(set_attr "mode" "HF")])
(define_insn "truncsfbf2"
- [(set (match_operand:BF 0 "register_operand" "=x, v")
+ [(set (match_operand:BF 0 "register_operand" "=x,x,v,Yv")
(float_truncate:BF
- (match_operand:SF 1 "register_operand" "x,v")))]
- "((TARGET_AVX512BF16 && TARGET_AVX512VL) || TARGET_AVXNECONVERT)
- && !HONOR_NANS (BFmode) && flag_unsafe_math_optimizations"
+ (match_operand:SF 1 "register_operand" "0,x,v,Yv")))]
+ "TARGET_SSE2 && flag_unsafe_math_optimizations && !HONOR_NANS (BFmode)"
"@
+ psrld\t{$16, %0|%0, 16}
%{vex%} vcvtneps2bf16\t{%1, %0|%0, %1}
- vcvtneps2bf16\t{%1, %0|%0, %1}"
- [(set_attr "isa" "avxneconvert,avx512bf16vl")
- (set_attr "prefix" "vex,evex")])
+ vcvtneps2bf16\t{%1, %0|%0, %1}
+ vpsrld\t{$16, %1, %0|%0, %1, 16}"
+ [(set_attr "isa" "noavx,avxneconvert,avx512bf16vl,avx")
+ (set_attr "prefix" "orig,vex,evex,vex")
+ (set_attr "type" "sseishft1,ssecvt,ssecvt,sseishft1")])
;; Signed conversion to DImode.
diff --git a/gcc/testsuite/gcc.target/i386/truncsfbf-1.c
b/gcc/testsuite/gcc.target/i386/truncsfbf-1.c
new file mode 100644
index 00000000000..dd3ff8a50b4
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/truncsfbf-1.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-msse2 -O2 -ffast-math" } */
+/* { dg-final { scan-assembler-times "psrld" 1 } } */
+
+__bf16
+foo (float a)
+{
+ return a;
+}
diff --git a/gcc/testsuite/gcc.target/i386/truncsfbf-2.c
b/gcc/testsuite/gcc.target/i386/truncsfbf-2.c
new file mode 100644
index 00000000000..f4952f88fc9
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/truncsfbf-2.c
@@ -0,0 +1,65 @@
+/* { dg-do run } */
+/* { dg-options "-msse2 -O2 -ffast-math" } */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <math.h>
+
+__bf16
+foo (float a)
+{
+ return a;
+}
+
+static __bf16
+CALC (float *a)
+{
+ uint32_t bits;
+ memcpy (&bits, a, sizeof (bits));
+ bits >>= 16;
+ uint16_t bfloat16_bits = (uint16_t) bits;
+ __bf16 bf16;
+ memcpy (&bf16, &bfloat16_bits, sizeof (bf16));
+ return bf16;
+}
+
+int
+main (void)
+{
+ float test_values[] = { 0.0f, -0.0f, 1.0f, -1.0f, 0.5f, -0.5f, 1000.0f,
-1000.0f,
+ 3.1415926f, -3.1415926f, 1e-8f, -1e-8f,
+ 1.0e+38f, -1.0e+38f, 1.0e-38f, -1.0e-38f };
+ size_t num_values = sizeof (test_values) / sizeof (test_values[0]);
+
+ for (size_t i = 0; i < num_values; ++i)
+ {
+ float original = test_values[i];
+ __bf16 hw_bf16 = foo (original);
+ __bf16 sw_bf16 = CALC (&original);
+
+ /* Verify psrld $16, %0 == %0 >> 16 */
+ if (memcmp (&hw_bf16, &sw_bf16, sizeof (__bf16)) != 0)
+ abort ();
+
+ /* Reconstruct the float value from the __bf16 bits */
+ uint16_t bf16_bits;
+ memcpy (&bf16_bits, &hw_bf16, sizeof (bf16_bits));
+ uint32_t reconstructed_bits = ((uint32_t) bf16_bits) << 16;
+ float converted;
+ memcpy (&converted, &reconstructed_bits, sizeof (converted));
+
+ float diff = fabsf (original - converted);
+
+ /* Expected Maximum Precision Loss */
+ uint32_t orig_bits;
+ memcpy (&orig_bits, &original, sizeof (orig_bits));
+ int exponent = ((orig_bits >> 23) & 0xFF) - 127;
+ float expected_loss = (exponent == -127)
+ ? ldexpf (1.0f, -126 - 7)
+ : ldexpf (1.0f, exponent - 7);
+ if (diff > expected_loss)
+ abort ();
+ }
+ return 0;
+}
--
2.31.1
