[Bug target/99863] [10/11 Regression] wrong code with -O -fno-tree-forwprop -mno-sse2

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99863

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Also time to fix this stupid veclower behavior:

   _7 = (unsigned int) _14;
   _5 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
-  v512u32_0_16 = _5 * v512u32_0_15(D);
+  _53 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
+  _54 = BIT_FIELD_REF <_53, 32, 0>;
+  _55 = BIT_FIELD_REF <v512u32_0_15(D), 32, 0>;
+  _56 = _54 * _55;
+  _57 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
+  _58 = BIT_FIELD_REF <_57, 32, 32>;
+  _59 = BIT_FIELD_REF <v512u32_0_15(D), 32, 32>;
+  _60 = _58 * _59;
...

instead of

   _5 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
-  v512u32_0_16 = _5 * v512u32_0_15(D);
   _54 = BIT_FIELD_REF <_5, 32, 0>;
...

or even better

   _5 = {_7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7, _7};
-  v512u32_0_16 = _5 * v512u32_0_15(D);
+  _55 = BIT_FIELD_REF <v512u32_0_15(D), 32, 0>;
+  _56 = _7 * _55;

it's all "fixed" later by CSE of course.

The error might be involving the clever handling of

-  v256u8_r_17 = _8 + _19;
+  _117 = BIT_FIELD_REF <_8, 64, 0>;
+  _118 = BIT_FIELD_REF <_19, 64, 0>;
+  _119 = _117 ^ _118;
+  _120 = _118 & 9187201950435737471;
+  _121 = _117 & 9187201950435737471;
+  _122 = _119 & 9259542123273814144;
+  _123 = _120 + _121;
+  _124 = _122 ^ _123;
+  _125 = BIT_FIELD_REF <_8, 64, 64>;
+  _126 = BIT_FIELD_REF <_19, 64, 64>;
...
+  _149 = {_124, _132, _140, _148};
+  _150 = VIEW_CONVERT_EXPR<v256u8>(_149);
+  v256u8_r_17 = _150;

it's enough to -fdisable-tree-forwprop4 (forwprop after veclower) to make
the problem show up so it might be as well an RTL optimization issue.