[InstSimplify] Handle some overflow intrinsics in InstSimplify

This change does a few things:
- Move some InstCombine transforms to InstSimplify
- Run SimplifyCall from within InstCombine::visitCallInst
- Teach InstSimplify to fold [us]mul_with_overflow(X, undef) to 0.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@237995 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/InstCombine/InstCombineCalls.cpp

@@ -13,6 +13,7 @@
 
 #include "InstCombineInternal.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Dominators.h"
@@ -323,6 +324,11 @@ static Value *SimplifyX86vperm2(const IntrinsicInst &II,
 /// the heavy lifting.
 ///
 Instruction *InstCombiner::visitCallInst(CallInst &CI) {
+  auto Args = CI.arg_operands();
+  if (Value *V = SimplifyCall(CI.getCalledValue(), Args.begin(), Args.end(), DL,
+                              TLI, DT, AC))
+    return ReplaceInstUsesWith(CI, V);
+
   if (isFreeCall(&CI, TLI))
     return visitFree(CI);
 

lib/Transforms/InstCombine/InstCombineCompares.cpp

@@ -2139,10 +2139,6 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
   }
   // FALL THROUGH uadd into sadd
   case OCF_SIGNED_ADD: {
-    // X + undef -> undef
-    if (isa<UndefValue>(RHS))
-      return SetResult(RHS, UndefValue::get(Builder->getInt1Ty()), false);
-
     // X + 0 -> {X, false}
     if (match(RHS, m_Zero()))
       return SetResult(LHS, Builder->getFalse(), false);
@@ -2157,14 +2153,6 @@ bool InstCombiner::OptimizeOverflowCheck(OverflowCheckFlavor OCF, Value *LHS,
 
   case OCF_UNSIGNED_SUB:
   case OCF_SIGNED_SUB: {
-    // undef - X -> undef
-    if (isa<UndefValue>(LHS))
-      return SetResult(LHS, UndefValue::get(Builder->getInt1Ty()), false);
-
-    // X - undef -> undef
-    if (isa<UndefValue>(RHS))
-      return SetResult(RHS, UndefValue::get(Builder->getInt1Ty()), false);
-
     // X - 0 -> {X, false}
     if (match(RHS, m_Zero()))
       return SetResult(LHS, Builder->getFalse(), false);