From 4a5b2040e20295e0f03fdbf15609ad5c137a6e3a Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Mon, 28 Nov 2011 22:37:34 +0000
Subject: [PATCH] Revert r145273 and fix in SelectionDAG::InferPtrAlignment()
 instead. Conservatively returns zero when the GV does not specify an
 alignment nor is it initialized. Previously it returns ABI alignment for type
 of the GV. However, if the type is a "packed" type, then the under-specified
 alignments is attached to the load / store instructions. In that case, the
 alignment of the type cannot be trusted. rdar://10464621

llvm-svn: 145300
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 38 ++++++-------------
 .../lib/CodeGen/SelectionDAG/SelectionDAG.cpp |  6 ++-
 llvm/test/CodeGen/X86/widen_load-1.ll         |  2 +-
 3 files changed, 18 insertions(+), 28 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 2c4886a3c83c..d8208a443387 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6206,20 +6206,13 @@ SDValue DAGCombiner::visitLOAD(SDNode *N) {
 
   // Try to infer better alignment information than the load already has.
   if (OptLevel != CodeGenOpt::None && LD->isUnindexed()) {
-    unsigned ABIAlign = TLI.getTargetData()->
-      getABITypeAlignment(LD->getMemoryVT().getTypeForEVT(*DAG.getContext()));
-    unsigned LDAlign = LD->getAlignment();
-    // Do not touch loads with explicit alignments that are smaller than ABI
-    // alignment to avoid breaking loads from "packed" types.
-    if (!LDAlign || LDAlign >= ABIAlign) {
-      if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
-        if (Align > LDAlign)
-          return DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
-                                LD->getValueType(0),
-                                Chain, Ptr, LD->getPointerInfo(),
-                                LD->getMemoryVT(),
-                                LD->isVolatile(), LD->isNonTemporal(), Align);
-      }
+    if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
+      if (Align > LD->getAlignment())
+        return DAG.getExtLoad(LD->getExtensionType(), N->getDebugLoc(),
+                              LD->getValueType(0),
+                              Chain, Ptr, LD->getPointerInfo(),
+                              LD->getMemoryVT(),
+                              LD->isVolatile(), LD->isNonTemporal(), Align);
     }
   }
 
@@ -6676,18 +6669,11 @@ SDValue DAGCombiner::visitSTORE(SDNode *N) {
 
   // Try to infer better alignment information than the store already has.
   if (OptLevel != CodeGenOpt::None && ST->isUnindexed()) {
-    unsigned ABIAlign = TLI.getTargetData()->
-      getABITypeAlignment(ST->getMemoryVT().getTypeForEVT(*DAG.getContext()));
-    unsigned STAlign = ST->getAlignment();
-    // Do not touch stores with explicit alignments that are smaller than ABI
-    // alignment to avoid breaking stores from "packed" types.
-    if (!STAlign || STAlign >= ABIAlign) {
-      if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
-        if (Align > STAlign)
-          return DAG.getTruncStore(Chain, N->getDebugLoc(), Value,
-                                   Ptr, ST->getPointerInfo(), ST->getMemoryVT(),
-                                   ST->isVolatile(), ST->isNonTemporal(),Align);
-      }
+    if (unsigned Align = DAG.InferPtrAlignment(Ptr)) {
+      if (Align > ST->getAlignment())
+        return DAG.getTruncStore(Chain, N->getDebugLoc(), Value,
+                                 Ptr, ST->getPointerInfo(), ST->getMemoryVT(),
+                                 ST->isVolatile(), ST->isNonTemporal(), Align);
     }
   }
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index a772a46ba60f..024a16373711 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6564,7 +6564,11 @@ unsigned SelectionDAG::InferPtrAlignment(SDValue Ptr) const {
         }
       }
       if (!Align)
-        Align = TLI.getTargetData()->getABITypeAlignment(GV->getType());
+        // Conservatively returns zero here instead of using ABI alignment for
+        // type of the GV. If the type is a "packed" type, then the under-
+        // specified alignments is attached to the load / store instructions.
+        // In that case, the alignment of the type cannot be trusted.
+        return 0;
     }
     return MinAlign(Align, GVOffset);
   }
diff --git a/llvm/test/CodeGen/X86/widen_load-1.ll b/llvm/test/CodeGen/X86/widen_load-1.ll
index a9fd19041840..9705d149ddcc 100644
--- a/llvm/test/CodeGen/X86/widen_load-1.ll
+++ b/llvm/test/CodeGen/X86/widen_load-1.ll
@@ -21,7 +21,7 @@ define void @reset(<2 x float>* noalias %garbage1) {
   store i32 0, i32* %changed, align 4
   %r2 = getelementptr float* bitcast ([20 x i64]* @compl to float*), i64 32 ; <float*> [#uses=1]
   %r3 = bitcast float* %r2 to <2 x float>*        ; <<2 x float>*> [#uses=1]
-  %r4 = load <2 x float>* %r3, align 8            ; <<2 x float>> [#uses=1]
+  %r4 = load <2 x float>* %r3, align 4            ; <<2 x float>> [#uses=1]
   call void @killcommon(i32* %changed)
   br label %"file complex.c, line 34, bb4"