https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100263
--- Comment #9 from Stefan Schulze Frielinghaus <stefansf at linux dot ibm.com>
---
Shouldn't we rather check for REG_CAN_CHANGE_MODE_P? A check for
TARGET_HARD_REGNO_MODE_OK for a FP register and QImode is successful.
Using the following also fixes the test for me:
diff --git a/gcc/postreload.c b/gcc/postreload.c
index dc67643384d..3dccbe63cf4 100644
--- a/gcc/postreload.c
+++ b/gcc/postreload.c
@@ -1733,7 +1733,7 @@ move2add_valid_value_p (int regno, scalar_int_mode mode)
regno of the lowpart might be different. */
poly_int64 s_off = subreg_lowpart_offset (mode, old_mode);
s_off = subreg_regno_offset (regno, old_mode, s_off, mode);
- if (maybe_ne (s_off, 0))
+ if (maybe_ne (s_off, 0) || !REG_CAN_CHANGE_MODE_P (regno, old_mode,
mode))
/* We could in principle adjust regno, check reg_mode[regno] to be
BLKmode, and return s_off to the caller (vs. -1 for failure),
but we currently have no callers that could make use of this
