[PATCH] D14078: [FPEnv Core 13/14] Don't hoist FP-ops with side-effects in LICM

[Sergey Dmitrouk via llvm-commits]

sdmitrouk updated this revision to Diff 41923.
sdmitrouk added a comment.

Rename flags.


Repository:
  rL LLVM

http://reviews.llvm.org/D14078

Files:
  lib/Transforms/Scalar/LICM.cpp
  test/Transforms/LICM/fpenv.ll

Index: test/Transforms/LICM/fpenv.ll
===================================================================
--- /dev/null
+++ test/Transforms/LICM/fpenv.ll
@@ -0,0 +1,30 @@
+; RUN: opt < %s -O3 -S | FileCheck %s
+
+define void @fdiv-is-not-hoisted-out-of-loop(i32 %n) {
+; CHECK-LABEL: @fdiv-is-not-hoisted-out-of-loop(
+; CHECK: for.body:
+; CHECK: fdiv
+entry:
+  %cmp2 = icmp sgt i32 %n, 0
+  br i1 %cmp2, label %for.body.lr.ph, label %for.end
+
+for.body.lr.ph:
+  %0 = add i32 %n, -1
+  br label %for.body
+
+for.body:
+  %i.03 = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.body ]
+  %div = fdiv double 0.000000e+00, 0.000000e+00
+  tail call void @process(double %div)
+  %inc = add nuw nsw i32 %i.03, 1
+  %exitcond = icmp eq i32 %i.03, %0
+  br i1 %exitcond, label %for.end.loopexit, label %for.body
+
+for.end.loopexit:
+  br label %for.end
+
+for.end:
+  ret void
+}
+
+declare void @process(double) nounwind
Index: lib/Transforms/Scalar/LICM.cpp
===================================================================
--- lib/Transforms/Scalar/LICM.cpp
+++ lib/Transforms/Scalar/LICM.cpp
@@ -694,6 +694,13 @@
   if (isSafeToSpeculativelyExecute(&Inst, CtxI, DT, TLI))
     return true;
 
+  // isSafeToSpeculativelyExecute() is not enough, because its result is
+  // taken into account only when it's positive and we need to forbid the case
+  // where its result is negative.
+  if (const FPMathOperator *MathOp = dyn_cast<FPMathOperator>(&Inst))
+    if (!MathOp->hasNoExceptions() || !MathOp->hasNoRounding())
+      return false;
+
   return isGuaranteedToExecute(Inst, DT, CurLoop, SafetyInfo);
 }
 


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