[llvm] 5d7afe2 - [Scalarizer] visit{Insert,Extract}ElementInst(): avoid call arg evaluation order deps

[Roman Lebedev via llvm-commits]

Author: Roman Lebedev
Date: 2020-07-06T13:42:35+03:00
New Revision: 5d7afe2d2e3c1a4715d022bfdb0c35df153e5430

URL: https://github.com/llvm/llvm-project/commit/5d7afe2d2e3c1a4715d022bfdb0c35df153e5430
DIFF: https://github.com/llvm/llvm-project/commit/5d7afe2d2e3c1a4715d022bfdb0c35df153e5430.diff

LOG: [Scalarizer] visit{Insert,Extract}ElementInst(): avoid call arg evaluation order deps

Compilers may evaluate call arguments in different order,
which would result in different order of IR, which would break the tests.

Spotted thanks to Dmitri Gribenko!

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/Scalarizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/Scalarizer.cpp b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
index a775be6ef7b8..5cac4dca8cf8 100644
--- a/llvm/lib/Transforms/Scalar/Scalarizer.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalarizer.cpp
@@ -769,10 +769,12 @@ bool ScalarizerVisitor::visitInsertElementInst(InsertElementInst &IEI) {
       return false;
 
     for (unsigned I = 0; I < NumElems; ++I) {
-      Res[I] = Builder.CreateSelect(
+      Value *ShouldReplace =
           Builder.CreateICmpEQ(InsIdx, ConstantInt::get(InsIdx->getType(), I),
-                               InsIdx->getName() + ".is." + Twine(I)),
-          NewElt, Op0[I], IEI.getName() + ".i" + Twine(I));
+                               InsIdx->getName() + ".is." + Twine(I));
+      Value *OldElt = Op0[I];
+      Res[I] = Builder.CreateSelect(ShouldReplace, NewElt, OldElt,
+                                    IEI.getName() + ".i" + Twine(I));
     }
   }
 
@@ -801,10 +803,12 @@ bool ScalarizerVisitor::visitExtractElementInst(ExtractElementInst &EEI) {
 
   Value *Res = UndefValue::get(VT->getElementType());
   for (unsigned I = 0; I < NumSrcElems; ++I) {
-    Res = Builder.CreateSelect(
+    Value *ShouldExtract =
         Builder.CreateICmpEQ(ExtIdx, ConstantInt::get(ExtIdx->getType(), I),
-                             ExtIdx->getName() + ".is." + Twine(I)),
-        Op0[I], Res, EEI.getName() + ".upto" + Twine(I));
+                             ExtIdx->getName() + ".is." + Twine(I));
+    Value *Elt = Op0[I];
+    Res = Builder.CreateSelect(ShouldExtract, Elt, Res,
+                               EEI.getName() + ".upto" + Twine(I));
   }
   gather(&EEI, {Res});
   return true;