From 4d09efd7b8fdf9e8a8c89bdb821f4992091a764b Mon Sep 17 00:00:00 2001 From: Evan Cheng <evan.cheng@apple.com> Date: Sat, 7 Jun 2008 08:52:29 +0000 Subject: 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 --- test/Transforms/SimplifyCFG/SpeculativeExec.ll | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) create mode 100644 test/Transforms/SimplifyCFG/SpeculativeExec.ll (limited to 'test/Transforms/SimplifyCFG/SpeculativeExec.ll') 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 +} -- cgit v1.1