From ec51f453381c4d03d67911730bfadd6eedf8d5e8 Mon Sep 17 00:00:00 2001
From: Rafael Espindola <rafael.espindola@gmail.com>
Date: Fri, 17 Oct 2014 21:25:48 +0000
Subject: [PATCH] Revert "TRE: make TRE a bit more aggressive"

This reverts commit r219899.

This also updates byval-tail-call.ll to make it clear what was breaking.
Adding r219899 again will cause the load/store to disappear.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220093 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../Scalar/TailRecursionElimination.cpp       | 10 ++++--
 test/Transforms/Inline/byval-tail-call.ll     |  8 +++--
 test/Transforms/TailCallElim/basic.ll         |  2 +-
 test/Transforms/TailCallElim/byval.ll         | 34 -------------------
 4 files changed, 14 insertions(+), 40 deletions(-)
 delete mode 100644 test/Transforms/TailCallElim/byval.ll

diff --git a/lib/Transforms/Scalar/TailRecursionElimination.cpp b/lib/Transforms/Scalar/TailRecursionElimination.cpp
index f8eafc845db..b7580255150 100644
--- a/lib/Transforms/Scalar/TailRecursionElimination.cpp
+++ b/lib/Transforms/Scalar/TailRecursionElimination.cpp
@@ -249,7 +249,12 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
     return false;
   AllCallsAreTailCalls = true;
 
+  // The local stack holds all alloca instructions and all byval arguments.
   AllocaDerivedValueTracker Tracker;
+  for (Argument &Arg : F.args()) {
+    if (Arg.hasByValAttr())
+      Tracker.walk(&Arg);
+  }
   for (auto &BB : F) {
     for (auto &I : BB)
       if (AllocaInst *AI = dyn_cast<AllocaInst>(&I))
@@ -305,8 +310,9 @@ bool TailCallElim::markTails(Function &F, bool &AllCallsAreTailCalls) {
         for (auto &Arg : CI->arg_operands()) {
           if (isa<Constant>(Arg.getUser()))
             continue;
-          if (isa<Argument>(Arg.getUser()))
-            continue;
+          if (Argument *A = dyn_cast<Argument>(Arg.getUser()))
+            if (!A->hasByValAttr())
+              continue;
           SafeToTail = false;
           break;
         }
diff --git a/test/Transforms/Inline/byval-tail-call.ll b/test/Transforms/Inline/byval-tail-call.ll
index e80bae1696e..154f3974b58 100644
--- a/test/Transforms/Inline/byval-tail-call.ll
+++ b/test/Transforms/Inline/byval-tail-call.ll
@@ -1,4 +1,4 @@
-; RUN: opt < %s -tailcallelim -inline -instcombine -dse -S | FileCheck %s
+; RUN: opt < %s -basicaa -tailcallelim -inline -instcombine -dse -S | FileCheck %s
 ; PR7272
 
 ; Calls that capture byval parameters cannot be marked as tail calls. Other
@@ -30,8 +30,10 @@ define internal void @qux(i32* byval %x) {
 
 define void @frob(i32* %x) {
 ; CHECK-LABEL: define void @frob(
-; CHECK: alloca i32
-; CHECK: {{^ *}}tail call void @ext(
+; CHECK: %[[POS:.*]] = alloca i32
+; CHECK: %[[VAL:.*]] = load i32* %x
+; CHECK: store i32 %[[VAL]], i32* %[[POS]]
+; CHECK: {{^ *}}call void @ext(i32* %[[POS]]
 ; CHECK: tail call void @ext(i32* null)
 ; CHECK: ret void
   tail call void @qux(i32* byval %x)
diff --git a/test/Transforms/TailCallElim/basic.ll b/test/Transforms/TailCallElim/basic.ll
index c7af9af5be7..8e9814b52bb 100644
--- a/test/Transforms/TailCallElim/basic.ll
+++ b/test/Transforms/TailCallElim/basic.ll
@@ -147,7 +147,7 @@ cond_false:
 ; Don't tail call if a byval arg is captured.
 define void @test9(i32* byval %a) {
 ; CHECK-LABEL: define void @test9(
-; CHECK: {{^ *}}tail call void @use(
+; CHECK: {{^ *}}call void @use(
   call void @use(i32* %a)
   ret void
 }
diff --git a/test/Transforms/TailCallElim/byval.ll b/test/Transforms/TailCallElim/byval.ll
deleted file mode 100644
index 1150f7684e9..00000000000
--- a/test/Transforms/TailCallElim/byval.ll
+++ /dev/null
@@ -1,34 +0,0 @@
-; RUN: opt -mtriple i386 -Os -S %s -o - | FileCheck %s
-; RUN: opt -mtriple x86_64 -Os -S %s -o - | FileCheck %s
-; RUN: opt -mtriple armv7 -Os -S %s -o - | FileCheck %s
-
-%struct.D16 = type { [16 x double] }
-
-declare void @_Z2OpP3D16PKS_S2_(%struct.D16*, %struct.D16*, %struct.D16*)
-
-define void @_Z7TestRefRK3D16S1_(%struct.D16* noalias sret %agg.result, %struct.D16* %RHS, %struct.D16* %LHS) {
-  %1 = alloca %struct.D16*, align 8
-  %2 = alloca %struct.D16*, align 8
-  store %struct.D16* %RHS, %struct.D16** %1, align 8
-  store %struct.D16* %LHS, %struct.D16** %2, align 8
-  %3 = load %struct.D16** %1, align 8
-  %4 = load %struct.D16** %2, align 8
-  call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %3, %struct.D16* %4)
-  ret void
-}
-
-; CHECK: define void @_Z7TestRefRK3D16S1_({{.*}}) {
-; CHECK:   tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
-; CHECK:   ret void
-; CHECK: }
-
-define void @_Z7TestVal3D16S_(%struct.D16* noalias sret %agg.result, %struct.D16* byval align 8 %RHS, %struct.D16* byval align 8 %LHS) {
-  call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
-  ret void
-}
-
-; CHECK: define void @_Z7TestVal3D16S_({{.*}}) {
-; CHECK:   tail call void @_Z2OpP3D16PKS_S2_(%struct.D16* %agg.result, %struct.D16* %RHS, %struct.D16* %LHS)
-; CHECK:   ret void
-; CHECK: }
-