[llvm-commits] [llvm] r114303 - /llvm/trunk/lib/Target/PowerPC/README.txt

[Chris Lattner]

Author: lattner
Date: Sat Sep 18 19:34:58 2010
New Revision: 114303

URL: http://llvm.org/viewvc/llvm-project?rev=114303&view=rev
Log:
add a readme.

Modified:
    llvm/trunk/lib/Target/PowerPC/README.txt

Modified: llvm/trunk/lib/Target/PowerPC/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/README.txt?rev=114303&r1=114302&r2=114303&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/README.txt (original)
+++ llvm/trunk/lib/Target/PowerPC/README.txt Sat Sep 18 19:34:58 2010
@@ -37,6 +37,31 @@
 	ori r3, r2, 65535
 	blr 
 
+===-------------------------------------------------------------------------===
+
+This code:
+
+unsigned add32carry(unsigned sum, unsigned x) {
+ unsigned z = sum + x;
+ if (sum + x < x)
+     z++;
+ return z;
+}
+
+Should compile to something like:
+
+	addc r3,r3,r4
+	addze r3,r3
+
+instead we get:
+
+	add r3, r4, r3
+	cmplw cr7, r3, r4
+	mfcr r4 ; 1
+	rlwinm r4, r4, 29, 31, 31
+	add r3, r3, r4
+
+Ick.
 
 ===-------------------------------------------------------------------------===