From ce562622118c40d5a24a07960c15cd4912db0cbf Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Thu, 18 Nov 2010 17:05:13 +0000
Subject: [PATCH] Add support for PHI-translating sext, zext, and trunc
 instructions, enabling more PRE. PR8586.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119704 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Analysis/PHITransAddr.cpp        | 44 ++++++++++++++++------------
 test/Transforms/GVN/phi-translate.ll | 31 ++++++++++++++++++++
 2 files changed, 57 insertions(+), 18 deletions(-)
 create mode 100644 test/Transforms/GVN/phi-translate.ll

diff --git a/lib/Analysis/PHITransAddr.cpp b/lib/Analysis/PHITransAddr.cpp
index a9ccab1f469..178d29e257d 100644
--- a/lib/Analysis/PHITransAddr.cpp
+++ b/lib/Analysis/PHITransAddr.cpp
@@ -20,9 +20,12 @@ using namespace llvm;
 
 static bool CanPHITrans(Instruction *Inst) {
   if (isa<PHINode>(Inst) ||
-      isa<BitCastInst>(Inst) ||
       isa<GetElementPtrInst>(Inst))
     return true;
+
+  if (isa<CastInst>(Inst) &&
+      Inst->isSafeToSpeculativelyExecute())
+    return true;
   
   if (Inst->getOpcode() == Instruction::Add &&
       isa<ConstantInt>(Inst->getOperand(1)))
@@ -177,26 +180,29 @@ Value *PHITransAddr::PHITranslateSubExpr(Value *V, BasicBlock *CurBB,
   // or because we just incorporated it into the expression).  See if its
   // operands need to be phi translated, and if so, reconstruct it.
   
-  if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
-    Value *PHIIn = PHITranslateSubExpr(BC->getOperand(0), CurBB, PredBB, DT);
+  if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
+    if (!Cast->isSafeToSpeculativelyExecute()) return 0;
+    Value *PHIIn = PHITranslateSubExpr(Cast->getOperand(0), CurBB, PredBB, DT);
     if (PHIIn == 0) return 0;
-    if (PHIIn == BC->getOperand(0))
-      return BC;
+    if (PHIIn == Cast->getOperand(0))
+      return Cast;
     
     // Find an available version of this cast.
     
     // Constants are trivial to find.
     if (Constant *C = dyn_cast<Constant>(PHIIn))
-      return AddAsInput(ConstantExpr::getBitCast(C, BC->getType()));
+      return AddAsInput(ConstantExpr::getCast(Cast->getOpcode(),
+                                              C, Cast->getType()));
     
-    // Otherwise we have to see if a bitcasted version of the incoming pointer
+    // Otherwise we have to see if a casted version of the incoming pointer
     // is available.  If so, we can use it, otherwise we have to fail.
     for (Value::use_iterator UI = PHIIn->use_begin(), E = PHIIn->use_end();
          UI != E; ++UI) {
-      if (BitCastInst *BCI = dyn_cast<BitCastInst>(*UI))
-        if (BCI->getType() == BC->getType() &&
-            (!DT || DT->dominates(BCI->getParent(), PredBB)))
-          return BCI;
+      if (CastInst *CastI = dyn_cast<CastInst>(*UI))
+        if (CastI->getOpcode() == Cast->getOpcode() &&
+            CastI->getType() == Cast->getType() &&
+            (!DT || DT->dominates(CastI->getParent(), PredBB)))
+          return CastI;
     }
     return 0;
   }
@@ -368,16 +374,18 @@ InsertPHITranslatedSubExpr(Value *InVal, BasicBlock *CurBB,
   // instruction.
   Instruction *Inst = cast<Instruction>(InVal);
   
-  // Handle bitcast of PHI translatable value.
-  if (BitCastInst *BC = dyn_cast<BitCastInst>(Inst)) {
-    Value *OpVal = InsertPHITranslatedSubExpr(BC->getOperand(0),
+  // Handle cast of PHI translatable value.
+  if (CastInst *Cast = dyn_cast<CastInst>(Inst)) {
+    if (!Cast->isSafeToSpeculativelyExecute()) return 0;
+    Value *OpVal = InsertPHITranslatedSubExpr(Cast->getOperand(0),
                                               CurBB, PredBB, DT, NewInsts);
     if (OpVal == 0) return 0;
     
-    // Otherwise insert a bitcast at the end of PredBB.
-    BitCastInst *New = new BitCastInst(OpVal, InVal->getType(),
-                                       InVal->getName()+".phi.trans.insert",
-                                       PredBB->getTerminator());
+    // Otherwise insert a cast at the end of PredBB.
+    CastInst *New = CastInst::Create(Cast->getOpcode(),
+                                     OpVal, InVal->getType(),
+                                     InVal->getName()+".phi.trans.insert",
+                                     PredBB->getTerminator());
     NewInsts.push_back(New);
     return New;
   }
diff --git a/test/Transforms/GVN/phi-translate.ll b/test/Transforms/GVN/phi-translate.ll
new file mode 100644
index 00000000000..f10537e0c93
--- /dev/null
+++ b/test/Transforms/GVN/phi-translate.ll
@@ -0,0 +1,31 @@
+; RUN: opt -basicaa -gvn -S < %s | FileCheck %s
+
+target datalayout = "e-p:64:64:64"
+
+; CHECK: @foo
+; CHECK: entry.end_crit_edge:
+; CHECK:   %n.pre = load i32* %q.phi.trans.insert
+; CHECK: then:
+; CHECK:   store i32 %z
+; CHECK: end:
+; CHECK:   %n = phi i32 [ %n.pre, %entry.end_crit_edge ], [ %z, %then ]
+; CHECK:   ret i32 %n
+
+@G = external global [100 x i32]
+define i32 @foo(i32 %x, i32 %z) {
+entry:
+  %tobool = icmp eq i32 %x, 0
+  br i1 %tobool, label %end, label %then
+
+then:
+  %i = sext i32 %x to i64
+  %p = getelementptr [100 x i32]* @G, i64 0, i64 %i
+  store i32 %z, i32* %p
+  br label %end
+
+end:
+  %j = sext i32 %x to i64
+  %q = getelementptr [100 x i32]* @G, i64 0, i64 %j
+  %n = load i32* %q
+  ret i32 %n
+}