[msan] Fix handling of select with struct arguments.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189796 91177308-0d34-0410-b5e6-96231b3b80d8
darkbasic · Sep 3, 2013 · 69086b2 · 69086b2
1 parent 6a9b29e
commit 69086b2
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Showing 2 changed files with 27 additions and 3 deletions.
diff --git a/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -1744,11 +1744,22 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
   void visitSelectInst(SelectInst& I) {
     IRBuilder<> IRB(&I);
     // a = select b, c, d
-    // Sa = (sext Sb) | (select b, Sc, Sd)
     Value *S = IRB.CreateSelect(I.getCondition(), getShadow(I.getTrueValue()),
                                 getShadow(I.getFalseValue()));
-    Value *S2 = IRB.CreateSExt(getShadow(I.getCondition()), S->getType());
-    setShadow(&I, IRB.CreateOr(S, S2, "_msprop"));
+    if (I.getType()->isAggregateType()) {
+      // To avoid "sign extending" i1 to an arbitrary aggregate type, we just do
+      // an extra "select". This results in much more compact IR.
+      // Sa = select Sb, poisoned, (select b, Sc, Sd)
+      S = IRB.CreateSelect(getShadow(I.getCondition()),
+                           getPoisonedShadow(getShadowTy(I.getType())), S,
+                           "_msprop_select_agg");
+    } else {
+      // Sa = (sext Sb) | (select b, Sc, Sd)
+      S = IRB.CreateOr(
+          S, IRB.CreateSExt(getShadow(I.getCondition()), S->getType()),
+          "_msprop_select");
+    }
+    setShadow(&I, S);
     if (MS.TrackOrigins) {
       // Origins are always i32, so any vector conditions must be flattened.
       // FIXME: consider tracking vector origins for app vectors?

diff --git a/test/Instrumentation/MemorySanitizer/msan_basic.ll b/test/Instrumentation/MemorySanitizer/msan_basic.ll
@@ -290,6 +290,19 @@ entry:
 ; CHECK-ORIGINS: ret <8 x i16>
 
 
+define { i64, i64 } @SelectStruct(i1 zeroext %x, { i64, i64 } %a, { i64, i64 } %b) readnone sanitize_memory {
+entry:
+  %c = select i1 %x, { i64, i64 } %a, { i64, i64 } %b
+  ret { i64, i64 } %c
+}
+
+; CHECK: @SelectStruct
+; CHECK: select i1 {{.*}}, { i64, i64 }
+; CHECK-NEXT: select i1 {{.*}}, { i64, i64 } { i64 -1, i64 -1 }, { i64, i64 }
+; CHECK-NEXT: select i1 {{.*}}, { i64, i64 }
+; CHECK: ret { i64, i64 }
+
+
 define i8* @IntToPtr(i64 %x) nounwind uwtable readnone sanitize_memory {
 entry:
   %0 = inttoptr i64 %x to i8*