1 files changed, 50 insertions, 0 deletions
diff --git a/test/Transforms/InstCombine/pr21210.ll b/test/Transforms/InstCombine/pr21210.ll
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+++ b/test/Transforms/InstCombine/pr21210.ll
@@ -0,0 +1,50 @@
+; RUN: opt < %s -mtriple=x86_64-unknown-linux-gnu -instcombine -S | FileCheck %s
+; Checks that the select-icmp optimization is safe in two cases
+declare void @foo(i32)
+declare i32 @bar(i32)
+
+; don't replace 'cond' by 'len' in the home block ('bb') that
+; contains the select
+define void @test1(i32 %len) {
+entry:
+  br label %bb
+
+bb:
+  %cmp = icmp ult i32 %len, 8
+  %cond = select i1 %cmp, i32 %len, i32 8
+  call void @foo(i32 %cond)
+  %cmp11 = icmp eq i32 %cond, 8
+  br i1 %cmp11, label %for.end, label %bb
+
+for.end:
+  ret void
+; CHECK: select
+; CHECK: icmp eq i32 %cond, 8
+}
+
+; don't replace 'cond' by 'len' in a block ('b1') that dominates all uses
+; of the select outside the home block ('bb'), but can be reached from the home
+; block on another path ('bb -> b0 -> b1')
+define void @test2(i32 %len) {
+entry:
+  %0 = call i32 @bar(i32 %len);
+  %cmp = icmp ult i32 %len, 4
+  br i1 %cmp, label %bb, label %b1
+bb:
+  %cond = select i1 %cmp, i32 %len, i32 8
+  %cmp11 = icmp eq i32 %cond, 8
+  br i1 %cmp11, label %b0, label %b1
+
+b0:
+  call void @foo(i32 %len)
+  br label %b1
+
+b1:
+; CHECK: phi i32 [ %cond, %bb ], [ undef, %b0 ], [ %0, %entry ]
+  %1 = phi i32 [ %cond, %bb ], [ undef, %b0 ], [ %0, %entry ]
+  br label %ret
+
+ret:
+  call void @foo(i32 %1)
+  ret void
+}