JumpThreading: Turn a select instruction into branching if it allows to thread one half of the select.
This is a common pattern coming out of simplifycfg generating gross code.
a: ; preds = %entry
%sel = select i1 %cmp1, double %add, double 0.
000000e+00
br label %b
b:
%cond5 = phi double [ %sel, %a ], [ %sub, %entry ]
%cmp6 = fcmp oeq double %cond5, 0.
000000e+00
br i1 %cmp6, label %if.then, label %if.end
becomes
a:
br i1 %cmp1, label %b, label %if.then
b:
%cond5 = phi double [ %sub, %entry ], [ %add, %a ]
%cmp6 = fcmp oeq double %cond5, 0.
000000e+00
br i1 %cmp6, label %if.then, label %if.end
Skipping block b completely if possible.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187880
91177308-0d34-0410-b5e6-
96231b3b80d8