[llvm] r290733 - [InstCombine] More thoroughly canonicalize the position of zexts

[David Majnemer via llvm-commits]

Author: majnemer
Date: Thu Dec 29 18:28:58 2016
New Revision: 290733

URL: http://llvm.org/viewvc/llvm-project?rev=290733&view=rev
Log:
[InstCombine] More thoroughly canonicalize the position of zexts

We correctly canonicalized (add (sext x), (sext y)) to (sext (add x, y))
where possible.  However, we didn't perform the same canonicalization
for zexts or for muls.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
    llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=290733&r1=290732&r2=290733&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Thu Dec 29 18:28:58 2016
@@ -1226,15 +1226,16 @@ Instruction *InstCombiner::visitAdd(Bina
   if (SExtInst *LHSConv = dyn_cast<SExtInst>(LHS)) {
     // (add (sext x), cst) --> (sext (add x, cst'))
     if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
-      Constant *CI =
-        ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
-      if (LHSConv->hasOneUse() &&
-          ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
-          WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, I)) {
-        // Insert the new, smaller add.
-        Value *NewAdd = Builder->CreateNSWAdd(LHSConv->getOperand(0),
-                                              CI, "addconv");
-        return new SExtInst(NewAdd, I.getType());
+      if (LHSConv->hasOneUse()) {
+        Constant *CI =
+            ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
+        if (ConstantExpr::getSExt(CI, I.getType()) == RHSC &&
+            WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, I)) {
+          // Insert the new, smaller add.
+          Value *NewAdd =
+              Builder->CreateNSWAdd(LHSConv->getOperand(0), CI, "addconv");
+          return new SExtInst(NewAdd, I.getType());
+        }
       }
     }
 
@@ -1255,6 +1256,43 @@ Instruction *InstCombiner::visitAdd(Bina
       }
     }
   }
+
+  // Check for (add (zext x), y), see if we can merge this into an
+  // integer add followed by a zext.
+  if (auto *LHSConv = dyn_cast<ZExtInst>(LHS)) {
+    // (add (zext x), cst) --> (zext (add x, cst'))
+    if (ConstantInt *RHSC = dyn_cast<ConstantInt>(RHS)) {
+      if (LHSConv->hasOneUse()) {
+        Constant *CI =
+            ConstantExpr::getTrunc(RHSC, LHSConv->getOperand(0)->getType());
+        if (ConstantExpr::getZExt(CI, I.getType()) == RHSC &&
+            WillNotOverflowSignedAdd(LHSConv->getOperand(0), CI, I)) {
+          // Insert the new, smaller add.
+          Value *NewAdd =
+              Builder->CreateNUWAdd(LHSConv->getOperand(0), CI, "addconv");
+          return new ZExtInst(NewAdd, I.getType());
+        }
+      }
+    }
+
+    // (add (zext x), (zext y)) --> (zext (add int x, y))
+    if (auto *RHSConv = dyn_cast<ZExtInst>(RHS)) {
+      // 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 add will not overflow.
+      if (LHSConv->getOperand(0)->getType() ==
+              RHSConv->getOperand(0)->getType() &&
+          (LHSConv->hasOneUse() || RHSConv->hasOneUse()) &&
+          computeOverflowForUnsignedAdd(LHSConv->getOperand(0),
+                                        RHSConv->getOperand(0),
+                                        &I) == OverflowResult::NeverOverflows) {
+        // Insert the new integer add.
+        Value *NewAdd = Builder->CreateNUWAdd(
+            LHSConv->getOperand(0), RHSConv->getOperand(0), "addconv");
+        return new ZExtInst(NewAdd, I.getType());
+      }
+    }
+  }
 
   // (add (xor A, B) (and A, B)) --> (or A, B)
   {

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp?rev=290733&r1=290732&r2=290733&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp Thu Dec 29 18:28:58 2016
@@ -389,6 +389,79 @@ Instruction *InstCombiner::visitMul(Bina
     }
   }
 
+  // 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);