[llvm-commits] [llvm] r122181 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCalls.cpp test/Transforms/InstCombine/intrinsics.ll

[Chris Lattner]

Author: lattner
Date: Sun Dec 19 13:35:32 2010
New Revision: 122181

URL: http://llvm.org/viewvc/llvm-project?rev=122181&view=rev
Log:
optimize uadd(x, cst) into a comparison when the normal 
result is dead.  This is required for my next patch to not
regress the testsuite.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/intrinsics.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp?rev=122181&r1=122180&r2=122181&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCalls.cpp Sun Dec 19 13:35:32 2010
@@ -523,6 +523,21 @@
         return InsertValueInst::Create(Struct, Add, 0);
       }
     }
+    
+    // If the normal result of the add is dead, and the RHS is a constant, we
+    // can transform this into a range comparison.
+    // overflow = uadd a, -4  -->  overflow = icmp ugt a, 3
+    if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS))
+      if (ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(II->use_back()))
+        if (II->hasOneUse() && EVI->getNumIndices() == 1 && !EVI->use_empty() &&
+            *EVI->idx_begin() == 1) {  // Extract of overflow result.
+          Builder->SetInsertPoint(EVI);
+          Value *R = Builder->CreateICmpUGT(LHS, ConstantExpr::getNot(CI));
+          R->takeName(EVI);
+          ReplaceInstUsesWith(*EVI, R);
+          return II;
+        }
+    
   }
   // FALL THROUGH uadd into sadd
   case Intrinsic::sadd_with_overflow:
@@ -550,6 +565,7 @@
         return InsertValueInst::Create(Struct, II->getArgOperand(0), 0);
       }
     }
+      
     break;
   case Intrinsic::usub_with_overflow:
   case Intrinsic::ssub_with_overflow:

Modified: llvm/trunk/test/Transforms/InstCombine/intrinsics.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/intrinsics.ll?rev=122181&r1=122180&r2=122181&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/intrinsics.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/intrinsics.ll Sun Dec 19 13:35:32 2010
@@ -71,6 +71,16 @@
 ; CHECK: ret i8 %A
 }
 
+define i1 @uaddtest6(i8 %A, i8 %B) {
+  %x = call %overflow.result @llvm.uadd.with.overflow.i8(i8 %A, i8 -4)
+  %z = extractvalue %overflow.result %x, 1
+  ret i1 %z
+; CHECK: @uaddtest6
+; CHECK-NEXT: %z = icmp ugt i8 %A, 3
+; CHECK-NEXT: ret i1 %z
+}
+
+
 define i8 @umultest1(i8 %A, i1* %overflowPtr) {
   %x = call %overflow.result @llvm.umul.with.overflow.i8(i8 0, i8 %A)
   %y = extractvalue %overflow.result %x, 0