[Committed] PR middle-end/102031: Fix typo/mistake in simplify_truncation patch

[Roger Sayle]

My apologies again.  My patch to simplify truncations of SUBREGs in
simplify-rtx.c contained an error where I'd accidentally compared
against a mode instead of the precision of that mode.  Grr!  It even
survived regression testing on two platforms.  Fixed below, and
committed as obvious, after a full "make bootstrap" and "make -k check"
on x86_64-pc-linux-gnu with no new regressions.


2021-08-24  Roger Sayle  <ro...@nextmovesoftware.com>

gcc/ChangeLog
        PR middle-end/102031
        * simplify-rtx.c (simplify_truncation): When comparing precisions
        use "subreg_prec" variable, not "subreg_mode".

Roger
--


diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 8eea9fb..c81e27e 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -841,7 +841,7 @@ simplify_context::simplify_truncation (machine_mode mode, 
rtx op,
        {
          unsigned int int_op_prec = GET_MODE_PRECISION (int_op_mode);
          unsigned int subreg_prec = GET_MODE_PRECISION (subreg_mode);
-         if (int_op_prec > subreg_mode)
+         if (int_op_prec > subreg_prec)
            {
              if (int_mode == subreg_mode)
                return SUBREG_REG (op);
@@ -851,7 +851,7 @@ simplify_context::simplify_truncation (machine_mode mode, 
rtx op,
            }
          /* Simplification of (truncate:A (subreg:B X:C 0)) where
             A is narrower than B and B is narrower than C.  */
-         else if (int_op_prec < subreg_mode
+         else if (int_op_prec < subreg_prec
                   && GET_MODE_PRECISION (int_mode) < int_op_prec)
            return simplify_gen_unary (TRUNCATE, int_mode,
                                       SUBREG_REG (op), subreg_mode);