From ae4664a9f2da955c9d2a3f38b28f0a4395851ace Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 5 Nov 2005 08:57:56 +0000 Subject: [PATCH] add a case Nate sent me git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@24195 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/PowerPC/README.txt | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/lib/Target/PowerPC/README.txt b/lib/Target/PowerPC/README.txt index 463e406779a..88582966994 100644 --- a/lib/Target/PowerPC/README.txt +++ b/lib/Target/PowerPC/README.txt @@ -217,3 +217,26 @@ _test: stw r2, 0(r3) blr +===-------------------------------------------------------------------------=== + +Compile this: + +int %f1(int %a, int %b) { + %tmp.1 = and int %a, 15 ; [#uses=1] + %tmp.3 = and int %b, 240 ; [#uses=1] + %tmp.4 = or int %tmp.3, %tmp.1 ; [#uses=1] + ret int %tmp.4 +} + +without a copy. We make this currently: + +_f1: + rlwinm r2, r4, 0, 24, 27 + rlwimi r2, r3, 0, 28, 31 + or r3, r2, r2 + blr + +The two-addr pass or RA needs to learn when it is profitable to commute an +instruction to avoid a copy AFTER the 2-addr instruction. The 2-addr pass +currently only commutes to avoid inserting a copy BEFORE the two addr instr. + -- 2.34.1