Hi!
When simplifying e.g. (float_truncate:SF (float_truncate:DF (reg:XF))
or (float_truncate:SF (float_extend:XF (reg:DF)) etc. into
(float_truncate:SF (reg:XF)) or (float_truncate:SF (reg:DF)) we call
simplify_gen_unary with incorrect op_mode argument, it should be
the argument's mode, but we call it with the outer mode instead.
As these are all floating point operations, the argument always
has non-VOIDmode and so we can just use that mode (as done in similar
simplifications a few lines later), but neither FLOAT_TRUNCATE nor
FLOAT_EXTEND are operations that should have the same modes of operand
and result. This bug hasn't been a problem for years because normally
op_mode is used only if the mode of op is VOIDmode, otherwise it is
redundant, but r10-2139 added an assertion in some spots that op_mode
is right even in such cases.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2024-01-31 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/113656
* simplify-rtx.cc (simplify_context::simplify_unary_operation_1)
<case FLOAT_TRUNCATE>: Fix up last argument to simplify_gen_unary.
* gcc.target/i386/pr113656.c: New test.
--- gcc/simplify-rtx.cc.jj 2024-01-03 11:51:32.828713189 +0100
+++ gcc/simplify-rtx.cc 2024-01-30 19:34:30.516934480 +0100
@@ -1305,7 +1305,7 @@ simplify_context::simplify_unary_operati
> GET_MODE_UNIT_SIZE (mode)
? FLOAT_TRUNCATE : FLOAT_EXTEND,
mode,
- XEXP (op, 0), mode);
+ XEXP (op, 0), GET_MODE (XEXP (op, 0)));
/* (float_truncate (float x)) is (float x) */
if ((GET_CODE (op) == FLOAT || GET_CODE (op) == UNSIGNED_FLOAT)
--- gcc/testsuite/gcc.target/i386/pr113656.c.jj 2024-01-30 19:38:29.029608721
+0100
+++ gcc/testsuite/gcc.target/i386/pr113656.c 2024-01-30 19:37:10.519703443
+0100
@@ -0,0 +1,12 @@
+/* PR rtl-optimization/113656 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -frounding-math -funsafe-math-optimizations -mavx512fp16
-mavx512vl" } */
+
+_Float16 a[8];
+
+void
+foo ()
+{
+ for (int i = 0; i < 8; i++)
+ a[i] = i - 8.4;
+}
Jakub
