On Wed, Aug 16, 2017 at 6:40 AM, Dibyendu Majumdar
<mobile@xxxxxxxxxxxxxxx> wrote:
> I think the linear output you obtained was post simplification. We
> need to look at the output prior to any simplifications. I believe it
> looks like this:
Before prompting memory variable to SSA form, the SSA form
is correct. That is my currently understanding. The incorrect SSA
form happen when we promote the memory variable into pseudo.
> Finally here is what clang does after some phases (initially clang
> starts with local vars).
>
> *** IR Dump After SROA ***
> ; Function Attrs: nounwind
> define void @foo() #0 {
> entry:
> %0 = load i32, i32* @a, align 4, !tbaa !1
> %tobool = icmp ne i32 %0, 0
> br i1 %tobool, label %if.then, label %if.else
>
> if.then: ; preds = %entry
> %1 = load i32, i32* @b, align 4, !tbaa !1
> br label %if.end
>
> if.else: ; preds = %entry
> %2 = load i32, i32* @c, align 4, !tbaa !1
> br label %if.end
>
> if.end: ; preds = %if.else, %if.then
> %e.0 = phi i32 [ %1, %if.then ], [ %2, %if.else ] <================
Notice how clang place the phi node at where I said it
need to be, basically the L3 in my email.
Also notice clang does not have phi source. It don't need to.
Chris
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