[llvm] r228731 - DeadArgElim: arguments affect all returned sub-values by default.

[Tim Northover]

Author: tnorthover
Date: Tue Feb 10 13:49:18 2015
New Revision: 228731

URL: http://llvm.org/viewvc/llvm-project?rev=228731&view=rev
Log:
DeadArgElim: arguments affect all returned sub-values by default.

Unless we meet an insertvalue on a path from some value to a return, that value
will be live if *any* of the return's components are live, so all of those
components must be added to the MaybeLiveUses.

Previously we were deleting arguments if sub-value 0 turned out to be dead.

Modified:
    llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp
    llvm/trunk/test/Transforms/DeadArgElim/aggregates.ll

Modified: llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp?rev=228731&r1=228730&r2=228731&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/DeadArgumentElimination.cpp Tue Feb 10 13:49:18 2015
@@ -146,7 +146,7 @@ namespace {
   private:
     Liveness MarkIfNotLive(RetOrArg Use, UseVector &MaybeLiveUses);
     Liveness SurveyUse(const Use *U, UseVector &MaybeLiveUses,
-                       unsigned RetValNum = 0);
+                       unsigned RetValNum = -1U);
     Liveness SurveyUses(const Value *V, UseVector &MaybeLiveUses);
 
     void SurveyFunction(const Function &F);
@@ -443,9 +443,21 @@ DAE::Liveness DAE::SurveyUse(const Use *
       // function's return value is live. We use RetValNum here, for the case
       // that U is really a use of an insertvalue instruction that uses the
       // original Use.
-      RetOrArg Use = CreateRet(RI->getParent()->getParent(), RetValNum);
-      // We might be live, depending on the liveness of Use.
-      return MarkIfNotLive(Use, MaybeLiveUses);
+      const Function *F = RI->getParent()->getParent();
+      if (RetValNum != -1U) {
+        RetOrArg Use = CreateRet(F, RetValNum);
+        // We might be live, depending on the liveness of Use.
+        return MarkIfNotLive(Use, MaybeLiveUses);
+      } else {
+        DAE::Liveness Result;
+        for (unsigned i = 0; i < NumRetVals(F); ++i) {
+          RetOrArg Use = CreateRet(F, i);
+          // We might be live, depending on the liveness of Use. All Results
+          // should be the same since they depend only on F.
+          Result = MarkIfNotLive(Use, MaybeLiveUses);
+        }
+        return Result;
+      }
     }
     if (const InsertValueInst *IV = dyn_cast<InsertValueInst>(V)) {
       if (U->getOperandNo() != InsertValueInst::getAggregateOperandIndex()

Modified: llvm/trunk/test/Transforms/DeadArgElim/aggregates.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/DeadArgElim/aggregates.ll?rev=228731&r1=228730&r2=228731&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/DeadArgElim/aggregates.ll (original)
+++ llvm/trunk/test/Transforms/DeadArgElim/aggregates.ll Tue Feb 10 13:49:18 2015
@@ -113,3 +113,20 @@ define void @test_can_shrink_arrays() {
 
   ret void
 }
+
+; Case 5: %in gets passed directly to the return. It should mark be marked as
+; used if *any* of the return values are, not just if value 0 is.
+
+; CHECK-LABEL: define internal i32 @ret_applies_to_all({ i32, i32 } %in)
+; CHECK: [[RET:%.*]] = extractvalue { i32, i32 } %in, 1
+; CHECK: ret i32 [[RET]]
+
+define internal {i32, i32} @ret_applies_to_all({i32, i32} %in) {
+  ret {i32, i32} %in
+}
+
+define i32 @test_ret_applies_to_all() {
+  %val = call {i32, i32} @ret_applies_to_all({i32, i32} {i32 42, i32 43})
+  %ret = extractvalue {i32, i32} %val, 1
+  ret i32 %ret
+}