From: Benjamin Kramer <benny.kra@googlemail.com>
Date: Tue, 12 Nov 2013 12:24:36 +0000 (+0000)
Subject: SimplifyCFG: Use existing constant folding logic when forming switch tables.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f681437cb082bf6fb5da43c8acd4e1313ba3b213;p=oota-llvm.git

SimplifyCFG: Use existing constant folding logic when forming switch tables.

Both simpler and more powerful than the hand-rolled folding logic.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@194475 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index d36d9dc1b96..d56bb329319 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -19,6 +19,7 @@
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ConstantFolding.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
@@ -3323,28 +3324,10 @@ static Constant *LookupConstant(Value *V,
 /// simple instructions such as binary operations where both operands are
 /// constant or can be replaced by constants from the ConstantPool. Returns the
 /// resulting constant on success, 0 otherwise.
-static Constant *ConstantFold(Instruction *I,
-                         const SmallDenseMap<Value*, Constant*>& ConstantPool) {
-  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
-    Constant *A = LookupConstant(BO->getOperand(0), ConstantPool);
-    if (!A)
-      return 0;
-    Constant *B = LookupConstant(BO->getOperand(1), ConstantPool);
-    if (!B)
-      return 0;
-    return ConstantExpr::get(BO->getOpcode(), A, B);
-  }
-
-  if (CmpInst *Cmp = dyn_cast<CmpInst>(I)) {
-    Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
-    if (!A)
-      return 0;
-    Constant *B = LookupConstant(I->getOperand(1), ConstantPool);
-    if (!B)
-      return 0;
-    return ConstantExpr::getCompare(Cmp->getPredicate(), A, B);
-  }
-
+static Constant *
+ConstantFold(Instruction *I,
+             const SmallDenseMap<Value *, Constant *> &ConstantPool,
+             const DataLayout *DL) {
   if (SelectInst *Select = dyn_cast<SelectInst>(I)) {
     Constant *A = LookupConstant(Select->getCondition(), ConstantPool);
     if (!A)
@@ -3356,14 +3339,19 @@ static Constant *ConstantFold(Instruction *I,
     return 0;
   }
 
-  if (CastInst *Cast = dyn_cast<CastInst>(I)) {
-    Constant *A = LookupConstant(I->getOperand(0), ConstantPool);
-    if (!A)
+  SmallVector<Constant *, 4> COps;
+  for (unsigned N = 0, E = I->getNumOperands(); N != E; ++N) {
+    if (Constant *A = LookupConstant(I->getOperand(N), ConstantPool))
+      COps.push_back(A);
+    else
       return 0;
-    return ConstantExpr::getCast(Cast->getOpcode(), A, Cast->getDestTy());
   }
 
-  return 0;
+  if (CmpInst *Cmp = dyn_cast<CmpInst>(I))
+    return ConstantFoldCompareInstOperands(Cmp->getPredicate(), COps[0],
+                                           COps[1], DL);
+
+  return ConstantFoldInstOperands(I->getOpcode(), I->getType(), COps, DL);
 }
 
 /// GetCaseResults - Try to determine the resulting constant values in phi nodes
@@ -3375,7 +3363,8 @@ GetCaseResults(SwitchInst *SI,
                ConstantInt *CaseVal,
                BasicBlock *CaseDest,
                BasicBlock **CommonDest,
-               SmallVectorImpl<std::pair<PHINode*,Constant*> > &Res) {
+               SmallVectorImpl<std::pair<PHINode *, Constant *> > &Res,
+               const DataLayout *DL) {
   // The block from which we enter the common destination.
   BasicBlock *Pred = SI->getParent();
 
@@ -3394,7 +3383,7 @@ GetCaseResults(SwitchInst *SI,
     } else if (isa<DbgInfoIntrinsic>(I)) {
       // Skip debug intrinsic.
       continue;
-    } else if (Constant *C = ConstantFold(I, ConstantPool)) {
+    } else if (Constant *C = ConstantFold(I, ConstantPool, DL)) {
       // Instruction is side-effect free and constant.
       ConstantPool.insert(std::make_pair(I, C));
     } else {
@@ -3718,7 +3707,7 @@ static bool SwitchToLookupTable(SwitchInst *SI,
     typedef SmallVector<std::pair<PHINode*, Constant*>, 4> ResultsTy;
     ResultsTy Results;
     if (!GetCaseResults(SI, CaseVal, CI.getCaseSuccessor(), &CommonDest,
-                        Results))
+                        Results, TD))
       return false;
 
     // Append the result from this case to the list for each phi.
@@ -3732,7 +3721,7 @@ static bool SwitchToLookupTable(SwitchInst *SI,
   // Get the resulting values for the default case.
   SmallVector<std::pair<PHINode*, Constant*>, 4> DefaultResultsList;
   if (!GetCaseResults(SI, 0, SI->getDefaultDest(), &CommonDest,
-                      DefaultResultsList))
+                      DefaultResultsList, TD))
     return false;
   for (size_t I = 0, E = DefaultResultsList.size(); I != E; ++I) {
     PHINode *PHI = DefaultResultsList[I].first;
diff --git a/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll b/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
index 71259c99b00..368732711a7 100644
--- a/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
+++ b/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
@@ -711,7 +711,7 @@ return:
   ret i32 %retval.0
 }
 
-define i32 @cprop(i32 %x) {
+define i32 @cprop(i32 %x, i32 %y) {
 entry:
   switch i32 %x, label %sw.default [
     i32 1, label %return
@@ -727,7 +727,8 @@ sw.bb1: br label %return
 
 sw.bb2:
   %and = and i32 %x, 1
-  %tobool = icmp ne i32 %and, 0
+  %and.ptr = inttoptr i32 %and to i8*
+  %tobool = icmp ne i8* %and.ptr, null
   %cond = select i1 %tobool, i32 -123, i32 456
   %sub = sub nsw i32 %x, %cond
   br label %return
@@ -735,13 +736,15 @@ sw.bb2:
 sw.bb3:
   %trunc = trunc i32 %x to i8
   %sext = sext i8 %trunc to i32
+  %select.i = icmp sgt i32 %sext, 0
+  %select = select i1 %select.i, i32 %sext, i32 %y
   br label %return
 
 sw.default:
   br label %return
 
 return:
-  %retval.0 = phi i32 [ 123, %sw.default ], [ %sext, %sw.bb3 ], [ %sub, %sw.bb2 ], [ 42, %sw.bb1 ], [ 5, %entry ]
+  %retval.0 = phi i32 [ 123, %sw.default ], [ %select, %sw.bb3 ], [ %sub, %sw.bb2 ], [ 42, %sw.bb1 ], [ 5, %entry ]
   ret i32 %retval.0
 
 ; CHECK-LABEL: @cprop(