Teach simplifycfg that setcc is cheap and non-trapping, so that it can

convert this:

        %tmp.1 = seteq int %i, 0                ; <bool> [#uses=1]
        br bool %tmp.1, label %shortcirc_done, label %shortcirc_next

shortcirc_next:         ; preds = %entry
        %tmp.4 = seteq int %j, 0                ; <bool> [#uses=1]
        br label %shortcirc_done

shortcirc_done:         ; preds = %shortcirc_next, %entry
        %shortcirc_val = phi bool [ %tmp.4, %shortcirc_next ], [ true, %entry ]         ; <bool> [#uses=1]

to this:
        %tmp.1 = seteq int %i, 0                ; <bool> [#uses=1]
        %tmp.4 = seteq int %j, 0                ; <bool> [#uses=1]
        %shortcirc_val = select bool %tmp.1, bool true, bool %tmp.4             ; <bool> [#uses=1]

... which is later simplified by instcombine into an or.

llvm-svn: 21388

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
index 12af5b04d59..986a53f11ff 100644
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -232,6 +232,12 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
       case Instruction::Xor:
       case Instruction::Shl:
       case Instruction::Shr:
+      case Instruction::SetEQ:
+      case Instruction::SetNE:
+      case Instruction::SetLT:
+      case Instruction::SetGT:
+      case Instruction::SetLE:
+      case Instruction::SetGE:
         break;   // These are all cheap and non-trapping instructions.
       }