diff options
| -rw-r--r-- | lib/Transforms/Utils/SimplifyCFG.cpp | 14 | ||||
| -rw-r--r-- | test/Transforms/SimplifyCFG/SpeculativeExec.ll | 42 |
2 files changed, 48 insertions, 8 deletions
diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index 7ec3165..11cb25d 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -1446,14 +1446,12 @@ static bool SpeculativelyExecuteBB(BranchInst *BI, BasicBlock *ThenBB) { if (Operator::getOpcode(CE) == Instruction::Select) return false; - // An unfolded ConstantExpr could end up getting expanded into - // Instructions. Don't speculate this and another instruction at - // the same time. - // FIXME: This is strange because provided we haven't already hit the cost - // of 1, this code will speculate an arbitrary number of complex constant - // expression PHI nodes. Also, this doesn't account for how complex the - // constant expression is. - if (SpeculationCost > 0) + // Account for the cost of an unfolded ConstantExpr which could end up + // getting expanded into Instructions. + // FIXME: This doesn't account for how many operations are combined in the + // constant expression. + ++SpeculationCost; + if (SpeculationCost > 1) return false; } diff --git a/test/Transforms/SimplifyCFG/SpeculativeExec.ll b/test/Transforms/SimplifyCFG/SpeculativeExec.ll index c66d3ec..7e27f41 100644 --- a/test/Transforms/SimplifyCFG/SpeculativeExec.ll +++ b/test/Transforms/SimplifyCFG/SpeculativeExec.ll @@ -66,3 +66,45 @@ end: ret i8* %x } + +define i8* @test4(i1* %dummy, i8* %a, i8* %b) { +; Test that we don't speculate an arbitrarily large number of unfolded constant +; expressions. +; CHECK: @test4 + +entry: + %cond1 = load volatile i1* %dummy + br i1 %cond1, label %if, label %end + +if: + %cond2 = load volatile i1* %dummy + br i1 %cond2, label %then, label %end + +then: + br label %end + +end: + %x1 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 1 to i8*), %then ] + %x2 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 2 to i8*), %then ] + %x3 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 3 to i8*), %then ] + %x4 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 4 to i8*), %then ] + %x5 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 5 to i8*), %then ] + %x6 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 6 to i8*), %then ] + %x7 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 7 to i8*), %then ] + %x8 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 8 to i8*), %then ] + %x9 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 9 to i8*), %then ] + %x10 = phi i8* [ %a, %entry ], [ %b, %if ], [ inttoptr (i64 10 to i8*), %then ] +; CHECK-NOT: select +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* +; CHECK: phi i8* + + ret i8* %x10 +} |