| commit | 20a607ebf4932abb113e18ed210127fbe8ff5f50 | [log] [tgz] |
|---|---|---|
| author | Evan Cheng <evan.cheng@apple.com> | Sat Jun 07 08:52:29 2008 +0000 |
| committer | Evan Cheng <evan.cheng@apple.com> | Sat Jun 07 08:52:29 2008 +0000 |
| tree | 80d8bef6f97f0aca27dbd0b30d6c75875e3f69f6 | |
| parent | 5f6d9d796df2a49e10586c92a6916d6b5b8fc09a [diff] [blame] |
Speculatively execute a block when the the block is the then part of a triangle shape and it contains a single, side effect free, cheap instruction. The branch is eliminated by adding a select instruction. i.e.
Turn
BB:
%t1 = icmp
br i1 %t1, label %BB1, label %BB2
BB1:
%t3 = add %t2, c
br label BB2
BB2:
=>
BB:
%t1 = icmp
%t4 = add %t2, c
%t3 = select i1 %t1, %t2, %t3
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52073 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Transforms/SimplifyCFG/SpeculativeExec.ll b/test/Transforms/SimplifyCFG/SpeculativeExec.ll new file mode 100644 index 0000000..2be9124 --- /dev/null +++ b/test/Transforms/SimplifyCFG/SpeculativeExec.ll
@@ -0,0 +1,21 @@ +; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep select +; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep br | count 2 + +define i32 @t2(i32 %a, i32 %b, i32 %c) nounwind { +entry: + %tmp1 = icmp eq i32 %b, 0 + br i1 %tmp1, label %bb1, label %bb3 + +bb1: ; preds = %entry + %tmp2 = icmp sgt i32 %c, 1 + br i1 %tmp2, label %bb2, label %bb3 + +bb2: ; preds = bb1 + %tmp3 = add i32 %a, 1 + br label %bb3 + +bb3: ; preds = %bb2, %entry + %tmp4 = phi i32 [ %b, %entry ], [ %a, %bb1 ], [ %tmp3, %bb2 ] + %tmp5 = sub i32 %tmp4, 1 + ret i32 %tmp5 +}