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      1 ; RUN: opt -early-cse -S < %s | FileCheck %s
      2 
      3 ; Can we CSE a known condition to a constant?
      4 define i1 @test(i8* %p) {
      5 ; CHECK-LABEL: @test
      6 entry:
      7   %cnd1 = icmp eq i8* %p, null
      8   br i1 %cnd1, label %taken, label %untaken
      9 
     10 taken:
     11 ; CHECK-LABEL: taken:
     12 ; CHECK-NEXT: ret i1 true
     13   %cnd2 = icmp eq i8* %p, null
     14   ret i1 %cnd2
     15 
     16 untaken:
     17 ; CHECK-LABEL: untaken:
     18 ; CHECK-NEXT: ret i1 false
     19   %cnd3 = icmp eq i8* %p, null
     20   ret i1 %cnd3
     21 }
     22 
     23 ; We can CSE the condition, but we *don't* know it's value after the merge
     24 define i1 @test_neg1(i8* %p) {
     25 ; CHECK-LABEL: @test_neg1
     26 entry:
     27   %cnd1 = icmp eq i8* %p, null
     28   br i1 %cnd1, label %taken, label %untaken
     29 
     30 taken:
     31   br label %merge
     32 
     33 untaken:
     34   br label %merge
     35 
     36 merge:
     37 ; CHECK-LABEL: merge:
     38 ; CHECK-NEXT: ret i1 %cnd1
     39   %cnd3 = icmp eq i8* %p, null
     40   ret i1 %cnd3
     41 }
     42 
     43 ; Check specifically for a case where we have a unique predecessor, but
     44 ; not a single predecessor.  We can not know the value of the condition here.
     45 define i1 @test_neg2(i8* %p) {
     46 ; CHECK-LABEL: @test_neg2
     47 entry:
     48   %cnd1 = icmp eq i8* %p, null
     49   br i1 %cnd1, label %merge, label %merge
     50 
     51 merge:
     52 ; CHECK-LABEL: merge:
     53 ; CHECK-NEXT: ret i1 %cnd1
     54   %cnd3 = icmp eq i8* %p, null
     55   ret i1 %cnd3
     56 }
     57 
     58 ; Replace a use rather than CSE
     59 define i1 @test2(i8* %p) {
     60 ; CHECK-LABEL: @test2
     61 entry:
     62   %cnd = icmp eq i8* %p, null
     63   br i1 %cnd, label %taken, label %untaken
     64 
     65 taken:
     66 ; CHECK-LABEL: taken:
     67 ; CHECK-NEXT: ret i1 true
     68   ret i1 %cnd
     69 
     70 untaken:
     71 ; CHECK-LABEL: untaken:
     72 ; CHECK-NEXT: ret i1 false
     73   ret i1 %cnd
     74 }
     75 
     76 ; Not legal to replace use given it's not dominated by edge
     77 define i1 @test2_neg1(i8* %p) {
     78 ; CHECK-LABEL: @test2_neg1
     79 entry:
     80   %cnd1 = icmp eq i8* %p, null
     81   br i1 %cnd1, label %taken, label %untaken
     82 
     83 taken:
     84   br label %merge
     85 
     86 untaken:
     87   br label %merge
     88 
     89 merge:
     90 ; CHECK-LABEL: merge:
     91 ; CHECK-NEXT: ret i1 %cnd1
     92   ret i1 %cnd1
     93 }
     94 
     95 ; Another single predecessor test, but for dominated use
     96 define i1 @test2_neg2(i8* %p) {
     97 ; CHECK-LABEL: @test2_neg2
     98 entry:
     99   %cnd1 = icmp eq i8* %p, null
    100   br i1 %cnd1, label %merge, label %merge
    101 
    102 merge:
    103 ; CHECK-LABEL: merge:
    104 ; CHECK-NEXT: ret i1 %cnd1
    105   ret i1 %cnd1
    106 }
    107 
    108