[llvm-commits] [llvm] r83295 - in /llvm/trunk: lib/Analysis/ConstantFolding.cpp test/Transforms/ConstProp/overflow-ops.ll

[Chris Lattner]

Author: lattner
Date: Mon Oct  5 00:26:04 2009
New Revision: 83295

URL: http://llvm.org/viewvc/llvm-project?rev=83295&view=rev
Log:
teach the optimizer how to constant fold uadd/usub intrinsics.

Added:
    llvm/trunk/test/Transforms/ConstProp/overflow-ops.ll
Modified:
    llvm/trunk/lib/Analysis/ConstantFolding.cpp

Modified: llvm/trunk/lib/Analysis/ConstantFolding.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ConstantFolding.cpp?rev=83295&r1=83294&r2=83295&view=diff

==============================================================================
--- llvm/trunk/lib/Analysis/ConstantFolding.cpp (original)
+++ llvm/trunk/lib/Analysis/ConstantFolding.cpp Mon Oct  5 00:26:04 2009
@@ -677,6 +677,8 @@
   case Intrinsic::ctpop:
   case Intrinsic::ctlz:
   case Intrinsic::cttz:
+  case Intrinsic::uadd_with_overflow:
+  case Intrinsic::usub_with_overflow:
     return true;
   default:
     return false;
@@ -756,7 +758,7 @@
   if (!F->hasName()) return 0;
   LLVMContext &Context = F->getContext();
   StringRef Name = F->getName();
-  
+
   const Type *Ty = F->getReturnType();
   if (NumOperands == 1) {
     if (ConstantFP *Op = dyn_cast<ConstantFP>(Operands[0])) {
@@ -881,6 +883,32 @@
       }
       return 0;
     }
+    
+    
+    if (ConstantInt *Op1 = dyn_cast<ConstantInt>(Operands[0])) {
+      if (ConstantInt *Op2 = dyn_cast<ConstantInt>(Operands[1])) {
+        switch (F->getIntrinsicID()) {
+        default: break;
+        case Intrinsic::uadd_with_overflow: {
+          Constant *Res = ConstantExpr::getAdd(Op1, Op2);           // result.
+          Constant *Ops[] = {
+            Res, ConstantExpr::getICmp(CmpInst::ICMP_ULT, Res, Op1) // overflow.
+          };
+          return ConstantStruct::get(F->getContext(), Ops, 2, false);
+        }
+        case Intrinsic::usub_with_overflow: {
+          Constant *Res = ConstantExpr::getSub(Op1, Op2);           // result.
+          Constant *Ops[] = {
+            Res, ConstantExpr::getICmp(CmpInst::ICMP_UGT, Res, Op1) // overflow.
+          };
+          return ConstantStruct::get(F->getContext(), Ops, 2, false);
+        }
+        }
+      }
+      
+      return 0;
+    }
+    return 0;
   }
   return 0;
 }

Added: llvm/trunk/test/Transforms/ConstProp/overflow-ops.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/ConstProp/overflow-ops.ll?rev=83295&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/ConstProp/overflow-ops.ll (added)
+++ llvm/trunk/test/Transforms/ConstProp/overflow-ops.ll Mon Oct  5 00:26:04 2009
@@ -0,0 +1,53 @@
+; RUN: opt < %s -constprop -S | FileCheck %s
+
+%i8i1 = type {i8, i1}
+
+;;-----------------------------
+;; uadd
+;;-----------------------------
+
+define {i8, i1} @uadd_1() nounwind {
+entry:
+  %t = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 42, i8 100)
+  ret {i8, i1} %t
+
+; CHECK: @uadd_1
+; CHECK: ret %i8i1 { i8 -114, i1 false }
+}
+
+define {i8, i1} @uadd_2() nounwind {
+entry:
+  %t = call {i8, i1} @llvm.uadd.with.overflow.i8(i8 142, i8 120)
+  ret {i8, i1} %t
+
+; CHECK: @uadd_2
+; CHECK: ret %i8i1 { i8 6, i1 true }
+}
+
+
+;;-----------------------------
+;; usub
+;;-----------------------------
+
+define {i8, i1} @usub_1() nounwind {
+entry:
+  %t = call {i8, i1} @llvm.usub.with.overflow.i8(i8 4, i8 2)
+  ret {i8, i1} %t
+
+; CHECK: @usub_1
+; CHECK: ret %i8i1 { i8 2, i1 false }
+}
+
+define {i8, i1} @usub_2() nounwind {
+entry:
+  %t = call {i8, i1} @llvm.usub.with.overflow.i8(i8 4, i8 6)
+  ret {i8, i1} %t
+
+; CHECK: @usub_2
+; CHECK: ret %i8i1 { i8 -2, i1 true }
+}
+
+
+
+declare {i8, i1} @llvm.uadd.with.overflow.i8(i8, i8)
+declare {i8, i1} @llvm.usub.with.overflow.i8(i8, i8)