1 files changed, 73 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index c70d7585cac..2f72e0ab6e9 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -389,6 +389,79 @@ Instruction *InstCombiner::visitMul(BinaryOperator &I) {
     }
   }
 
+  // Check for (mul (sext x), y), see if we can merge this into an
+  // integer mul followed by a sext.
+  if (SExtInst *Op0Conv = dyn_cast<SExtInst>(Op0)) {
+    // (mul (sext x), cst) --> (sext (mul x, cst'))
+    if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
+      if (Op0Conv->hasOneUse()) {
+        Constant *CI =
+            ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
+        if (ConstantExpr::getSExt(CI, I.getType()) == Op1C &&
+            WillNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
+          // Insert the new, smaller mul.
+          Value *NewMul =
+              Builder->CreateNSWMul(Op0Conv->getOperand(0), CI, "mulconv");
+          return new SExtInst(NewMul, I.getType());
+        }
+      }
+    }
+
+    // (mul (sext x), (sext y)) --> (sext (mul int x, y))
+    if (SExtInst *Op1Conv = dyn_cast<SExtInst>(Op1)) {
+      // Only do this if x/y have the same type, if at last one of them has a
+      // single use (so we don't increase the number of sexts), and if the
+      // integer mul will not overflow.
+      if (Op0Conv->getOperand(0)->getType() ==
+              Op1Conv->getOperand(0)->getType() &&
+          (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
+          WillNotOverflowSignedMul(Op0Conv->getOperand(0),
+                                   Op1Conv->getOperand(0), I)) {
+        // Insert the new integer mul.
+        Value *NewMul = Builder->CreateNSWMul(
+            Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
+        return new SExtInst(NewMul, I.getType());
+      }
+    }
+  }
+
+  // Check for (mul (zext x), y), see if we can merge this into an
+  // integer mul followed by a zext.
+  if (auto *Op0Conv = dyn_cast<ZExtInst>(Op0)) {
+    // (mul (zext x), cst) --> (zext (mul x, cst'))
+    if (ConstantInt *Op1C = dyn_cast<ConstantInt>(Op1)) {
+      if (Op0Conv->hasOneUse()) {
+        Constant *CI =
+            ConstantExpr::getTrunc(Op1C, Op0Conv->getOperand(0)->getType());
+        if (ConstantExpr::getZExt(CI, I.getType()) == Op1C &&
+            WillNotOverflowSignedMul(Op0Conv->getOperand(0), CI, I)) {
+          // Insert the new, smaller mul.
+          Value *NewMul =
+              Builder->CreateNUWMul(Op0Conv->getOperand(0), CI, "mulconv");
+          return new ZExtInst(NewMul, I.getType());
+        }
+      }
+    }
+
+    // (mul (zext x), (zext y)) --> (zext (mul int x, y))
+    if (auto *Op1Conv = dyn_cast<ZExtInst>(Op1)) {
+      // Only do this if x/y have the same type, if at last one of them has a
+      // single use (so we don't increase the number of zexts), and if the
+      // integer mul will not overflow.
+      if (Op0Conv->getOperand(0)->getType() ==
+              Op1Conv->getOperand(0)->getType() &&
+          (Op0Conv->hasOneUse() || Op1Conv->hasOneUse()) &&
+          computeOverflowForUnsignedMul(Op0Conv->getOperand(0),
+                                        Op1Conv->getOperand(0),
+                                        &I) == OverflowResult::NeverOverflows) {
+        // Insert the new integer mul.
+        Value *NewMul = Builder->CreateNUWMul(
+            Op0Conv->getOperand(0), Op1Conv->getOperand(0), "mulconv");
+        return new ZExtInst(NewMul, I.getType());
+      }
+    }
+  }
+
   if (!I.hasNoSignedWrap() && WillNotOverflowSignedMul(Op0, Op1, I)) {
     Changed = true;
     I.setHasNoSignedWrap(true);