From: Richard Stallman <rms@gnu.org>
Date: Mon, 24 May 1993 07:45:54 +0000 (+0000)
Subject: (subst): For subreg-of-constant, don't gen_lowpart
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=19808e22caa8929ed61043340b832b5c51d4012a;p=gcc.git

(subst): For subreg-of-constant, don't gen_lowpart
if it's a big-endian machine and constant is multi-word.

From-SVN: r4554
---

diff --git a/gcc/combine.c b/gcc/combine.c
index ca1567c6f0e..49e214eecbf 100644
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -3085,8 +3085,16 @@ subst (x, from, to, in_dest, unique_copy)
 	    return temp;
 	}
 	
+      /* If we want a subreg of a constant, at offset 0,
+	 take the low bits.  On a little-endian machine, that's
+	 always valid.  On a big-endian machine, it's valid
+	 only if the constant's mode fits in one word.  */
       if (CONSTANT_P (SUBREG_REG (x)) && subreg_lowpart_p (x)
-	  && GET_MODE_SIZE (mode) < GET_MODE_SIZE (op0_mode))
+	  && GET_MODE_SIZE (mode) < GET_MODE_SIZE (op0_mode)
+#if WORDS_BIG_ENDIAN
+	  && GET_MODE_BITSIZE (op0_mode) < BITS_PER_WORD
+#endif
+	  )
 	return gen_lowpart_for_combine (mode, SUBREG_REG (x));
 
       /* If we are narrowing the object, we need to see if we can simplify