From: Roger Sayle <roger@nextmovesoftware.com>
Date: Wed, 24 Jun 2020 19:18:03 +0000 (+0000)
Subject: simplify-rtx: Simplify rotates by zero
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0c586913e61021681e3221e8760cd87b24142aea;p=gcc.git

simplify-rtx: Simplify rotates by zero

2020-06-24  Roger Sayle  <roger@nextmovesoftware.com>
	    Segher Boessenkool  <segher@kernel.crashing.org>

	* simplify-rtx.c (simplify_unary_operation_1): Simplify rotates by 0.
---

diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 65008eaab45..3e913b5dd4f 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -3645,6 +3645,8 @@ simplify_binary_operation_1 (enum rtx_code code, machine_mode mode,
 
     case ROTATERT:
     case ROTATE:
+      if (trueop1 == CONST0_RTX (mode))
+	return op0;
       /* Canonicalize rotates by constant amount.  If op1 is bitsize / 2,
 	 prefer left rotation, if op1 is from bitsize / 2 + 1 to
 	 bitsize - 1, use other direction of rotate with 1 .. bitsize / 2 - 1