From a9cf5b3cc9082acee5b6e30e989a667fed286b05 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Sat, 23 Jan 2010 18:42:37 +0000
Subject: add a note

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94317 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/PowerPC/README.txt | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

(limited to 'lib/Target/PowerPC/README.txt')

diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt
index 060d6a5c5c..a243543cd4 100644
--- a/lib/Target/PowerPC/README.txt
+++ b/lib/Target/PowerPC/README.txt
@@ -635,6 +635,35 @@ This sort of thing occurs a lot due to globalopt.
 
 ===-------------------------------------------------------------------------===
 
+We compile:
+
+define i32 @bar(i32 %x) nounwind readnone ssp {
+entry:
+  %0 = icmp eq i32 %x, 0                          ; <i1> [#uses=1]
+  %neg = select i1 %0, i32 -1, i32 0              ; <i32> [#uses=1]
+  ret i32 %neg
+}
+
+to:
+
+_bar:
+	cmplwi cr0, r3, 0
+	li r3, -1
+	beq cr0, LBB1_2
+; BB#1:                                                     ; %entry
+	li r3, 0
+LBB1_2:                                                     ; %entry
+	blr 
+
+it would be much better to produce:
+
+_bar: 
+        addic r3,r3,-1
+        subfe r3,r3,r3
+        blr
+
+===-------------------------------------------------------------------------===
+
 We currently compile 32-bit bswap:
 
 declare i32 @llvm.bswap.i32(i32 %A)
-- 
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