don't hoist FP additions into unconditional adds + selects. This

could theoretically introduce a trap, but is also a performance issue.
This speeds up ptrdist/ks by 8%.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45533 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index b838f94b79096019a3b8fa9389278f7c50e734d4..f19adbd263cab789eda6a269b062943bc3da40d2 100644 (file)
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -372,6 +372,8 @@ static bool DominatesMergePoint(Value *V, BasicBlock *BB,
       case Instruction::AShr:
       case Instruction::ICmp:
       case Instruction::FCmp:
+        if (I->getOperand(0)->getType()->isFPOrFPVector())
+          return false;  // FP arithmetic might trap.
         break;   // These are all cheap and non-trapping instructions.
       }
 

diff --git a/test/Transforms/SimplifyCFG/2008-01-02-hoist-fp-add.ll b/test/Transforms/SimplifyCFG/2008-01-02-hoist-fp-add.ll
new file mode 100644 (file)
index 0000000..43ff690
--- /dev/null
+++ b/test/Transforms/SimplifyCFG/2008-01-02-hoist-fp-add.ll
@@ -0,0 +1,26 @@
+; The phi should not be eliminated in this case, because the fp op could trap.
+; RUN: llvm-as < %s | opt -simplifycfg | llvm-dis | grep {= phi double}
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i686-apple-darwin8"
+@G = weak global double 0.000000e+00, align 8          ; <double*> [#uses=2]
+
+define void @test(i32 %X, i32 %Y, double %Z) {
+entry:
+       %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
+       %tmp = load double* @G, align 8         ; <double> [#uses=2]
+       %tmp3 = icmp eq i32 %X, %Y              ; <i1> [#uses=1]
+       %tmp34 = zext i1 %tmp3 to i8            ; <i8> [#uses=1]
+       %toBool = icmp ne i8 %tmp34, 0          ; <i1> [#uses=1]
+       br i1 %toBool, label %cond_true, label %cond_next
+
+cond_true:             ; preds = %entry
+       %tmp7 = add double %tmp, %Z             ; <double> [#uses=1]
+       br label %cond_next
+
+cond_next:             ; preds = %cond_true, %entry
+       %F.0 = phi double [ %tmp, %entry ], [ %tmp7, %cond_true ]               ; <double> [#uses=1]
+       store double %F.0, double* @G, align 8
+       ret void
+}
+