[llvm-commits] [llvm] r145300 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp lib/CodeGen/SelectionDAG/SelectionDAG.cpp test/CodeGen/X86/widen_load-1.ll

[Evan Cheng]

Author: evancheng
Date: Mon Nov 28 16:37:34 2011
New Revision: 145300

URL: http://llvm.org/viewvc/llvm-project?rev=145300&view=rev
Log:
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

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
    llvm/trunk/test/CodeGen/X86/widen_load-1.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=145300&r1=145299&r2=145300&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Mon Nov 28 16:37:34 2011
@@ -6206,20 +6206,13 @@
 
   // 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 @@
 
   // 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);
     }
   }
 

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=145300&r1=145299&r2=145300&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Mon Nov 28 16:37:34 2011
@@ -6564,7 +6564,11 @@
         }
       }
       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);
   }

Modified: llvm/trunk/test/CodeGen/X86/widen_load-1.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/widen_load-1.ll?rev=145300&r1=145299&r2=145300&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/widen_load-1.ll (original)
+++ llvm/trunk/test/CodeGen/X86/widen_load-1.ll Mon Nov 28 16:37:34 2011
@@ -21,7 +21,7 @@
   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"