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llvm-6502/test/Transforms/SimplifyCFG/PhiBlockMerge.ll
Chris Lattner 60d410d7bb fix two significant issues with FoldTwoEntryPHINode:
first, it can kick in on blocks whose conditions have been
folded to a constant, even though one of the edges will be
trivially folded.

second, it doesn't clean up the "if diamond" that it just 
eliminated away.  This is a problem because other simplifycfg
xforms kick in depending on the order of block visitation,
causing pointless work.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121762 91177308-0d34-0410-b5e6-96231b3b80d8
2010-12-14 08:01:53 +00:00

26 lines
749 B
LLVM

; Test merging of blocks that only have PHI nodes in them
;
; RUN: opt < %s -simplifycfg -S | FileCheck %s
;
define i32 @test(i1 %a, i1 %b) {
; CHECK: br i1 %a
br i1 %a, label %M, label %O
O: ; preds = %0
; CHECK: select i1 %b, i32 0, i32 1
; CHECK-NOT: phi
br i1 %b, label %N, label %Q
Q: ; preds = %O
br label %N
N: ; preds = %Q, %O
; This block should be foldable into M
%Wp = phi i32 [ 0, %O ], [ 1, %Q ] ; <i32> [#uses=1]
br label %M
M: ; preds = %N, %0
; CHECK: %W = phi i32
%W = phi i32 [ %Wp, %N ], [ 2, %0 ] ; <i32> [#uses=1]
%R = add i32 %W, 1 ; <i32> [#uses=1]
ret i32 %R
}