[llvm-commits] [llvm] r168970 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll

[Evan Cheng]

Author: evancheng
Date: Thu Nov 29 20:02:42 2012
New Revision: 168970

URL: http://llvm.org/viewvc/llvm-project?rev=168970&view=rev
Log:
Fix logic to determine whether to turn a switch into a lookup table. When
the tables cannot fit in registers (i.e. bitmap), do not emit the table
if it's using an illegal type.

rdar://12779436

Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
    llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=168970&r1=168969&r2=168970&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Nov 29 20:02:42 2012
@@ -3511,22 +3511,29 @@
 static bool ShouldBuildLookupTable(SwitchInst *SI,
                                    uint64_t TableSize,
                                    const DataLayout *TD,
+                                   const TargetTransformInfo *TTI,
                             const SmallDenseMap<PHINode*, Type*>& ResultTypes) {
   // The table density should be at least 40%. This is the same criterion as for
   // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
   // FIXME: Find the best cut-off.
   if (SI->getNumCases() > TableSize || TableSize >= UINT64_MAX / 10)
     return false; // TableSize overflowed, or mul below might overflow.
-  if (SI->getNumCases() * 10 >= TableSize * 4)
-    return true;
 
   // If each table would fit in a register, we should build it anyway.
+  bool AllFit = true;
+  bool HasIllegalType = false;
   for (SmallDenseMap<PHINode*, Type*>::const_iterator I = ResultTypes.begin(),
        E = ResultTypes.end(); I != E; ++I) {
-    if (!SwitchLookupTable::WouldFitInRegister(TD, TableSize, I->second))
-      return false;
+    Type *Ty = I->second;
+    if (!TTI->getScalarTargetTransformInfo()->isTypeLegal(Ty))
+      HasIllegalType = true;
+    if (!SwitchLookupTable::WouldFitInRegister(TD, TableSize, Ty)) {
+      AllFit = false;
+      break;
+    }
   }
-  return true;
+
+  return AllFit || (!HasIllegalType && (SI->getNumCases() * 10 >= TableSize * 4));
 }
 
 /// SwitchToLookupTable - If the switch is only used to initialize one or more
@@ -3607,7 +3614,7 @@
 
   APInt RangeSpread = MaxCaseVal->getValue() - MinCaseVal->getValue();
   uint64_t TableSize = RangeSpread.getLimitedValue() + 1;
-  if (!ShouldBuildLookupTable(SI, TableSize, TD, ResultTypes))
+  if (!ShouldBuildLookupTable(SI, TableSize, TD, TTI, ResultTypes))
     return false;
 
   // Create the BB that does the lookups.

Modified: llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll?rev=168970&r1=168969&r2=168970&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll Thu Nov 29 20:02:42 2012
@@ -777,3 +777,29 @@
 ; CHECK: switch.lookup:
 ; CHECK: getelementptr inbounds [5 x i32]* @switch.table6, i32 0, i32 %switch.tableidx
 }
+
+; Don't create a table with illegal type
+; rdar://12779436
+define i96 @illegaltype(i32 %c) {
+entry:
+  switch i32 %c, label %sw.default [
+    i32 42, label %return
+    i32 43, label %sw.bb1
+    i32 44, label %sw.bb2
+    i32 45, label %sw.bb3
+    i32 46, label %sw.bb4
+  ]
+
+sw.bb1: br label %return
+sw.bb2: br label %return
+sw.bb3: br label %return
+sw.bb4: br label %return
+sw.default: br label %return
+return:
+  %retval.0 = phi i96 [ 15, %sw.default ], [ 27, %sw.bb4 ], [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ]
+  ret i96 %retval.0
+
+; CHECK: @illegaltype
+; CHECK-NOT: @switch.table
+; CHECK: switch i32 %c
+}