remove unary since fneg only case. copy NUW or NSW over from orig binOp to new binOp.

Author: farzonl

llvm/lib/Target/DirectX/DXILLegalizePass.cpp

@@ -70,15 +70,21 @@ static bool fixI8TruncUseChain(Instruction &I,
     }
 
     Value *NewInst = nullptr;
-    if (auto *BO = dyn_cast<BinaryOperator>(&I))
+    if (auto *BO = dyn_cast<BinaryOperator>(&I)) {
       NewInst =
           Builder.CreateBinOp(BO->getOpcode(), NewOperands[0], NewOperands[1]);
-    else if (Cmp) {
+
+      if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(&I)) {
+        if (OBO->hasNoSignedWrap())
+          cast<BinaryOperator>(NewInst)->setHasNoSignedWrap();
+        if (OBO->hasNoUnsignedWrap())
+          cast<BinaryOperator>(NewInst)->setHasNoUnsignedWrap();
+      }
+    } else if (Cmp) {
       NewInst = Builder.CreateCmp(Cmp->getPredicate(), NewOperands[0],
                                   NewOperands[1]);
       Cmp->replaceAllUsesWith(NewInst);
-    } else if (auto *UnaryOp = dyn_cast<UnaryOperator>(&I))
-      NewInst = Builder.CreateUnOp(UnaryOp->getOpcode(), NewOperands[0]);
+    }
 
     if (NewInst) {
       ReplacedValues[&I] = NewInst;

llvm/test/CodeGen/DirectX/legalize-i8.ll

@@ -12,7 +12,7 @@ define i32 @removal_only_test(i32 %a) {
 define i32 @i8trunc(float %0) #0 {
   ; CHECK-LABEL: define i32 @i8trunc(
   ; CHECK-NOT: %4 = trunc nsw i32 %3 to i8
-  ; CHECK: add i32
+  ; CHECK: add nsw i32
   ; CHECK-NEXT: srem i32
   ; CHECK-NEXT: sub i32
   ; CHECK-NEXT: mul i32