From b613f8842e77483311483b628c68e3c4e857cc77 Mon Sep 17 00:00:00 2001
From: Tim Northover <tnorthover@apple.com>
Date: Tue, 10 Feb 2015 19:49:18 +0000
Subject: [PATCH] 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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@228731 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../IPO/DeadArgumentElimination.cpp           | 20 +++++++++++++++----
 test/Transforms/DeadArgElim/aggregates.ll     | 17 ++++++++++++++++
 2 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/lib/Transforms/IPO/DeadArgumentElimination.cpp b/lib/Transforms/IPO/DeadArgumentElimination.cpp
index 50698bb26c8..596204dac62 100644
--- a/lib/Transforms/IPO/DeadArgumentElimination.cpp
+++ b/lib/Transforms/IPO/DeadArgumentElimination.cpp
@@ -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 *U,
       // 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()
diff --git a/test/Transforms/DeadArgElim/aggregates.ll b/test/Transforms/DeadArgElim/aggregates.ll
index 153289947c1..84370834e11 100644
--- a/test/Transforms/DeadArgElim/aggregates.ll
+++ b/test/Transforms/DeadArgElim/aggregates.ll
@@ -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
+}