From: Richard Kenner <kenner@vlsi1.ultra.nyu.edu>
Date: Tue, 18 Apr 2000 19:14:58 +0000 (-0400)
Subject: expmed.c (emit_store_flag): If comparing two-word integer with zero, can optimize... 
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=6912b84bf1a10c6bc8c9c337153189a44bdce35f;p=gcc.git

expmed.c (emit_store_flag): If comparing two-word integer with zero, can optimize NE, EQ, GE, and LT.

	* expmed.c (emit_store_flag): If comparing two-word integer
	with zero, can optimize NE, EQ, GE, and LT.

From-SVN: r33230
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0ba9d8b55be..d9eb7c4b0c3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,14 +1,17 @@
-2000-04-18  Mark Mitchell  <mark@codesourcery.com>
-
-	* cpplex.c (_cpp_lex_token): Don't call CPP_BUMP_LINE when the
-	mark is active.
-
 Tue Apr 18 14:16:47 2000  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
 
+	* expmed.c (emit_store_flag): If comparing two-word integer
+	with zero, can optimize NE, EQ, GE, and LT.
+
 	* c-decl.c (mark_binding_level): Use 'for' instead of `while'.
 	* conflict.c: Minor cleanups.
 	* optabs.c: Add blank line
-	* simplify-rtx.c: 
+	* simplify-rtx.c: Minor cleanups.
+
+2000-04-18  Mark Mitchell  <mark@codesourcery.com>
+
+	* cpplex.c (_cpp_lex_token): Don't call CPP_BUMP_LINE when the
+	mark is active.
 
 2000-04-17  Zack Weinberg  <zack@wolery.cumb.org>
 
diff --git a/gcc/expmed.c b/gcc/expmed.c
index 16c9bef6b5f..bb06536e5e5 100644
--- a/gcc/expmed.c
+++ b/gcc/expmed.c
@@ -4181,6 +4181,29 @@ emit_store_flag (target, code, op0, op1, mode, unsignedp, normalizep)
       break;
     }
 
+  /* If we are comparing a double-word integer with zero, we can convert
+     the comparison into one involving a single word.  */
+  if (GET_MODE_BITSIZE (mode) == BITS_PER_WORD * 2
+      && GET_MODE_CLASS (mode) == MODE_INT
+      && op1 == const0_rtx)
+    {
+      if (code == EQ || code == NE)
+	{
+	  /* Do a logical OR of the two words and compare the result.  */
+	  rtx op0h = gen_highpart (word_mode, op0);
+	  rtx op0l = gen_lowpart (word_mode, op0);
+	  rtx op0both = expand_binop (word_mode, ior_optab, op0h, op0l,
+				      NULL_RTX, unsignedp, OPTAB_DIRECT);
+	  if (op0both != 0)
+	    return emit_store_flag (target, code, op0both, op1, word_mode,
+				    unsignedp, normalizep);
+	}
+      else if (code == LT || code == GE)
+	/* If testing the sign bit, can just test on high word.  */
+	return emit_store_flag (target, code, gen_highpart (word_mode, op0),
+				op1, word_mode, unsignedp, normalizep);
+    }
+
   /* From now on, we won't change CODE, so set ICODE now.  */
   icode = setcc_gen_code[(int) code];