From a3351a0e5db0b5b2c53920f2f15d3e862fecfad3 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Sat, 4 Jun 2011 06:48:50 +0000
Subject: [PATCH] Disable the main feature of 130180, the elimination of loads
 that are redundant with partially-aliasing loads.

When computing what portion of a clobbering load value is needed,
it doesn't consider phi-translation which may have occurred
between the clobbing load and the redundant load.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132631 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/MemoryDependenceAnalysis.cpp |  6 ++++++
 test/Transforms/GVN/rle.ll                | 24 +++++++++++------------
 2 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/lib/Analysis/MemoryDependenceAnalysis.cpp b/lib/Analysis/MemoryDependenceAnalysis.cpp
index a412425770f..5f640c01d25 100644
--- a/lib/Analysis/MemoryDependenceAnalysis.cpp
+++ b/lib/Analysis/MemoryDependenceAnalysis.cpp
@@ -374,10 +374,16 @@ getPointerDependencyFrom(const AliasAnalysis::Location &MemLoc, bool isLoad,
         if (R == AliasAnalysis::MustAlias)
           return MemDepResult::getDef(Inst);
 
+#if 0 // FIXME: Temporarily disabled. GVN is cleverly rewriting loads
+      // in terms of clobbering loads, but since it does this by looking
+      // at the clobbering load directly, it doesn't know about any
+      // phi translation that may have happened along the way.
+
         // If we have a partial alias, then return this as a clobber for the
         // client to handle.
         if (R == AliasAnalysis::PartialAlias)
           return MemDepResult::getClobber(Inst);
+#endif
         
         // Random may-alias loads don't depend on each other without a
         // dependence.
diff --git a/test/Transforms/GVN/rle.ll b/test/Transforms/GVN/rle.ll
index 51f2727f1c8..28b1fc7b607 100644
--- a/test/Transforms/GVN/rle.ll
+++ b/test/Transforms/GVN/rle.ll
@@ -562,14 +562,14 @@ entry:
   %add = add nsw i32 %tmp2, %conv
   ret i32 %add
 
-; CHECK: @load_load_partial_alias
-; CHECK: load i32*
-; CHECK-NOT: load
-; CHECK: lshr i32 {{.*}}, 8
-; CHECK-NOT: load
-; CHECK: trunc i32 {{.*}} to i8
-; CHECK-NOT: load
-; CHECK: ret i32
+; TEMPORARILYDISABLED: @load_load_partial_alias
+; TEMPORARILYDISABLED: load i32*
+; TEMPORARILYDISABLED-NOT: load
+; TEMPORARILYDISABLED: lshr i32 {{.*}}, 8
+; TEMPORARILYDISABLED-NOT: load
+; TEMPORARILYDISABLED: trunc i32 {{.*}} to i8
+; TEMPORARILYDISABLED-NOT: load
+; TEMPORARILYDISABLED: ret i32
 }
 
 
@@ -589,10 +589,10 @@ land.lhs.true:                                    ; preds = %entry
 
 if.end:
   ret i32 52
-; CHECK: @load_load_partial_alias_cross_block
-; CHECK: land.lhs.true:
-; CHECK-NOT: load i8
-; CHECK: ret i32 %conv6
+; TEMPORARILY_DISABLED: @load_load_partial_alias_cross_block
+; TEMPORARILY_DISABLED: land.lhs.true:
+; TEMPORARILY_DISABLED-NOT: load i8
+; TEMPORARILY_DISABLED: ret i32 %conv6
 }
 
 
-- 
2.34.1