commit 58cfa3b13752579c86cf85270d49f9ced0942f2f
author Dan Gohman <gohman@apple.com> Tue Aug 25 22:11:20 2009 +0000
committer Dan Gohman <gohman@apple.com> Tue Aug 25 22:11:20 2009 +0000
tree e2d88c43f06255610357c7c9ee6caa8883523454
parent 415c8cf837439401f2df75d992d7e296d1d6746a

Rename Instruction::isIdenticalTo to Instruction::isIdenticalToWhenDefined,
and introduce a new Instruction::isIdenticalTo which tests for full
identity, including the SubclassOptionalData flags. Also, fix the
Instruction::clone implementations to preserve the SubclassOptionalData
flags. Finally, teach several optimizations how to handle
SubclassOptionalData correctly, given these changes.

This fixes the counterintuitive behavior of isIdenticalTo not comparing
the full value, and clone not returning an identical clone, as well as
some subtle bugs that could be caused by these.

Thanks to Nick Lewycky for reporting this, and for an initial patch!


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80038 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/IPO/MergeFunctions.cpp

diff --git a/lib/Transforms/IPO/MergeFunctions.cpp b/lib/Transforms/IPO/MergeFunctions.cpp
index f037c4f..9c8592e 100644
--- a/lib/Transforms/IPO/MergeFunctions.cpp
+++ b/lib/Transforms/IPO/MergeFunctions.cpp
@@ -188,7 +188,8 @@
 isEquivalentOperation(const Instruction *I1, const Instruction *I2) {
   if (I1->getOpcode() != I2->getOpcode() ||
       I1->getNumOperands() != I2->getNumOperands() ||
-      !isEquivalentType(I1->getType(), I2->getType()))
+      !isEquivalentType(I1->getType(), I2->getType()) ||
+      !I1->hasSameSubclassOptionalData(I2))
     return false;
 
   // We have two instructions of identical opcode and #operands.  Check to see

lib/Transforms/Scalar/InstructionCombining.cpp

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 6dd2641..cca428e 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -11815,12 +11815,16 @@
   if (A == B) return true;
   
   // Test if the values come form identical arithmetic instructions.
+  // This uses isIdenticalToWhenDefined instead of isIdenticalTo because
+  // its only used to compare two uses within the same basic block, which
+  // means that they'll always either have the same value or one of them
+  // will have an undefined value.
   if (isa<BinaryOperator>(A) ||
       isa<CastInst>(A) ||
       isa<PHINode>(A) ||
       isa<GetElementPtrInst>(A))
     if (Instruction *BI = dyn_cast<Instruction>(B))
-      if (cast<Instruction>(A)->isIdenticalTo(BI))
+      if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
         return true;
   
   // Otherwise they may not be equivalent.

lib/Transforms/Utils/BasicBlockUtils.cpp

diff --git a/lib/Transforms/Utils/BasicBlockUtils.cpp b/lib/Transforms/Utils/BasicBlockUtils.cpp
index 3072cee..c3d6194 100644
--- a/lib/Transforms/Utils/BasicBlockUtils.cpp
+++ b/lib/Transforms/Utils/BasicBlockUtils.cpp
@@ -504,11 +504,15 @@
   // Test if the values are trivially equivalent.
   if (A == B) return true;
   
-  // Test if the values come form identical arithmetic instructions.
+  // Test if the values come from identical arithmetic instructions.
+  // Use isIdenticalToWhenDefined instead of isIdenticalTo because
+  // this function is only used when one address use dominates the
+  // other, which means that they'll always either have the same
+  // value or one of them will have an undefined value.
   if (isa<BinaryOperator>(A) || isa<CastInst>(A) ||
       isa<PHINode>(A) || isa<GetElementPtrInst>(A))
     if (const Instruction *BI = dyn_cast<Instruction>(B))
-      if (cast<Instruction>(A)->isIdenticalTo(BI))
+      if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI))
         return true;
   
   // Otherwise they may not be equivalent.

lib/Transforms/Utils/SimplifyCFG.cpp

diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp
index 7b7495e..0938c44 100644
--- a/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -872,7 +872,7 @@
   while (isa<DbgInfoIntrinsic>(I2))
     I2 = BB2_Itr++;
   if (I1->getOpcode() != I2->getOpcode() || isa<PHINode>(I1) ||
-      !I1->isIdenticalTo(I2) ||
+      !I1->isIdenticalToWhenDefined(I2) ||
       (isa<InvokeInst>(I1) && !isSafeToHoistInvoke(BB1, BB2, I1, I2)))
     return false;
 
@@ -891,6 +891,7 @@
     BIParent->getInstList().splice(BI, BB1->getInstList(), I1);
     if (!I2->use_empty())
       I2->replaceAllUsesWith(I1);
+    I1->intersectOptionalDataWith(I2);
     BB2->getInstList().erase(I2);
 
     I1 = BB1_Itr++;
@@ -899,7 +900,8 @@
     I2 = BB2_Itr++;
     while (isa<DbgInfoIntrinsic>(I2))
       I2 = BB2_Itr++;
-  } while (I1->getOpcode() == I2->getOpcode() && I1->isIdenticalTo(I2));
+  } while (I1->getOpcode() == I2->getOpcode() &&
+           I1->isIdenticalToWhenDefined(I2));
 
   return true;