From 88d84b245cf3e09d41f7b1d2520dd6011a87f7b6 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 2 Dec 2008 06:32:34 +0000 Subject: [PATCH] add a note git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@60404 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Target/README.txt | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 3c689dbe46e..518c9893c8c 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -1252,3 +1252,24 @@ have the concept of a "C signed subtraction" operator that which is undefined on overflow. //===---------------------------------------------------------------------===// + +This was noticed in the entryblock for grokdeclarator in 403.gcc: + + %tmp = icmp eq i32 %decl_context, 4 + %decl_context_addr.0 = select i1 %tmp, i32 3, i32 %decl_context + %tmp1 = icmp eq i32 %decl_context_addr.0, 1 + %decl_context_addr.1 = select i1 %tmp1, i32 0, i32 %decl_context_addr.0 + +tmp1 should be simplified to something like: + (!tmp || decl_context == 1) + +This allows recursive simplifications, tmp1 is used all over the place in +the function, e.g. by: + + %tmp23 = icmp eq i32 %decl_context_addr.1, 0 ; [#uses=1] + %tmp24 = xor i1 %tmp1, true ; [#uses=1] + %or.cond8 = and i1 %tmp23, %tmp24 ; [#uses=1] + +later. + +