[llvm-commits] [llvm] r92921 - /llvm/trunk/lib/Target/PowerPC/README.txt

[Chris Lattner]

Author: lattner
Date: Thu Jan  7 11:53:10 2010
New Revision: 92921

URL: http://llvm.org/viewvc/llvm-project?rev=92921&view=rev
Log:
constant materialization could be improved.

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=92921&r1=92920&r2=92921&view=diff

==============================================================================
--- llvm/trunk/lib/Target/PowerPC/README.txt (original)
+++ llvm/trunk/lib/Target/PowerPC/README.txt Thu Jan  7 11:53:10 2010
@@ -7,6 +7,39 @@
 
 ===-------------------------------------------------------------------------===
 
+On PPC64, this:
+
+long f2 (long x) { return 0xfffffff000000000UL; }
+long f3 (long x) { return 0x1ffffffffUL; }
+
+could compile into:
+
+_f2:
+	li r3,-1
+	rldicr r3,r3,0,27
+	blr
+_f3:
+	li r3,-1
+	rldicl r3,r3,0,31
+	blr
+
+we produce:
+
+_f2:
+	lis r2, 4095
+	ori r2, r2, 65535
+	sldi r3, r2, 36
+	blr 
+_f3:
+	li r2, 1
+	sldi r2, r2, 32
+	oris r2, r2, 65535
+	ori r3, r2, 65535
+	blr 
+
+
+===-------------------------------------------------------------------------===
+
 Support 'update' load/store instructions.  These are cracked on the G5, but are
 still a codesize win.