Hopefully fixed by http://lists.cs.uiuc.edu/pipermail/llvm-commits/
Week-of-Mon-20071217/056446.html
This is my first attempt hacking on Transforms, so some of the idioms
were a little new to me. Hope the patch looks OK! =)
On Dec 17, 2007, at 5:19 PM, Chris Lattner wrote:
Author: lattner
Date: Mon Dec 17 19:19:18 2007
New Revision: 45141
URL: http://llvm.org/viewvc/llvm-project?rev=45141&view=rev
Log:
add a missed case.
Modified:
llvm/trunk/lib/Target/README.txt
Modified: llvm/trunk/lib/Target/README.txt
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/
README.txt?rev=45141&r1=45140&r2=45141&view=diff
======================================================================
========
--- llvm/trunk/lib/Target/README.txt (original)
+++ llvm/trunk/lib/Target/README.txt Mon Dec 17 19:19:18 2007
@@ -464,3 +464,21 @@
}
//
===-------------------------------------------------------------------
--===//
+
+This code is often produced by the SMAX expansion in SCEV:
+
+define i32 @foo(i32 %a) {
+entry:
+ %tmp15 = sub i32 99, %a ; <i32> [#uses=2]
+ %tmp16 = icmp slt i32 %tmp15, 0 ; <i1> [#uses=1]
+ %smax = select i1 %tmp16, i32 0, i32 %tmp15 ;
<i32> [#uses=1]
+ %tmp12 = add i32 %smax, %a ; <i32> [#uses=1]
+ %tmp13 = add i32 %tmp12, 1 ; <i32> [#uses=1]
+ ret i32 %tmp13
+}
+
+Note that the tmp12 add can be pushed through the select operands,
turning
+it into a "select %tmp16, %a, 99". We apparently already do this
in dag
+combine because it isn't present in X86 output.
+
+//
===-------------------------------------------------------------------
--===//
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--
Christopher Lamb
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