[llvm] r364235 - InstCombine: Preserve nuw when reassociating nuw ops [3/3]

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Mon Jun 24 14:37:03 2019
New Revision: 364235

URL: http://llvm.org/viewvc/llvm-project?rev=364235&view=rev
Log:
InstCombine: Preserve nuw when reassociating nuw ops [3/3]

Alive says this is OK.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp?rev=364235&r1=364234&r2=364235&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Mon Jun 24 14:37:03 2019
@@ -590,32 +590,44 @@ Value *InstCombiner::tryFactorization(Bi
     ++NumFactor;
     SimplifiedInst->takeName(&I);
 
-    // Check if we can add NSW flag to SimplifiedInst. If so, set NSW flag.
-    // TODO: Check for NUW.
+    // Check if we can add NSW/NUW flags to SimplifiedInst. If so, set them.
     if (BinaryOperator *BO = dyn_cast<BinaryOperator>(SimplifiedInst)) {
       if (isa<OverflowingBinaryOperator>(SimplifiedInst)) {
         bool HasNSW = false;
-        if (isa<OverflowingBinaryOperator>(&I))
+        bool HasNUW = false;
+        if (isa<OverflowingBinaryOperator>(&I)) {
           HasNSW = I.hasNoSignedWrap();
+          HasNUW = I.hasNoUnsignedWrap();
+        }
 
-        if (auto *LOBO = dyn_cast<OverflowingBinaryOperator>(LHS))
+        if (auto *LOBO = dyn_cast<OverflowingBinaryOperator>(LHS)) {
           HasNSW &= LOBO->hasNoSignedWrap();
+          HasNUW &= LOBO->hasNoUnsignedWrap();
+        }
 
-        if (auto *ROBO = dyn_cast<OverflowingBinaryOperator>(RHS))
+        if (auto *ROBO = dyn_cast<OverflowingBinaryOperator>(RHS)) {
           HasNSW &= ROBO->hasNoSignedWrap();
+          HasNUW &= ROBO->hasNoUnsignedWrap();
+        }
 
-        // We can propagate 'nsw' if we know that
-        //  %Y = mul nsw i16 %X, C
-        //  %Z = add nsw i16 %Y, %X
-        // =>
-        //  %Z = mul nsw i16 %X, C+1
-        //
-        // iff C+1 isn't INT_MIN
         const APInt *CInt;
         if (TopLevelOpcode == Instruction::Add &&
-            InnerOpcode == Instruction::Mul)
-          if (match(V, m_APInt(CInt)) && !CInt->isMinSignedValue())
-            BO->setHasNoSignedWrap(HasNSW);
+            InnerOpcode == Instruction::Mul) {
+          // We can propagate 'nsw' if we know that
+          //  %Y = mul nsw i16 %X, C
+          //  %Z = add nsw i16 %Y, %X
+          // =>
+          //  %Z = mul nsw i16 %X, C+1
+          //
+          // iff C+1 isn't INT_MIN
+          if (match(V, m_APInt(CInt))) {
+            if (!CInt->isMinSignedValue())
+              BO->setHasNoSignedWrap(HasNSW);
+          }
+
+          // nuw can be propagated with any constant or nuw value.
+          BO->setHasNoUnsignedWrap(HasNUW);
+        }
       }
     }
   }

Modified: llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll?rev=364235&r1=364234&r2=364235&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll Mon Jun 24 14:37:03 2019
@@ -92,7 +92,7 @@ define i32 @reassoc_x2_sub_nuw(i32 %x, i
 
 define i32 @tryFactorization_add_nuw_mul_nuw(i32 %x) {
 ; CHECK-LABEL: @tryFactorization_add_nuw_mul_nuw(
-; CHECK-NEXT:    [[ADD2:%.*]] = shl i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[ADD2:%.*]] = shl nuw i32 [[X:%.*]], 2
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;
   %mul1 = mul nuw i32 %x, 3
@@ -102,7 +102,7 @@ define i32 @tryFactorization_add_nuw_mul
 
 define i32 @tryFactorization_add_nuw_mul_nuw_int_max(i32 %x) {
 ; CHECK-LABEL: @tryFactorization_add_nuw_mul_nuw_int_max(
-; CHECK-NEXT:    [[ADD2:%.*]] = shl i32 [[X:%.*]], 31
+; CHECK-NEXT:    [[ADD2:%.*]] = shl nuw i32 [[X:%.*]], 31
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;
   %mul1 = mul nuw i32 %x, 2147483647
@@ -129,3 +129,51 @@ define i32 @tryFactorization_add_nuw_mul
   %add2 = add i32 %mul1, %x
   ret i32 %add2
 }
+
+define i32 @tryFactorization_add_nuw_mul_nuw_mul_nuw_var(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @tryFactorization_add_nuw_mul_nuw_mul_nuw_var(
+; CHECK-NEXT:    [[MUL21:%.*]] = add i32 [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[ADD1:%.*]] = mul nuw i32 [[MUL21]], [[X:%.*]]
+; CHECK-NEXT:    ret i32 [[ADD1]]
+;
+  %mul1 = mul nuw i32 %x, %y
+  %mul2 = mul nuw i32 %x, %z
+  %add1 = add nuw i32 %mul1, %mul2
+  ret i32 %add1
+}
+
+define i32 @tryFactorization_add_nuw_mul_mul_nuw_var(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @tryFactorization_add_nuw_mul_mul_nuw_var(
+; CHECK-NEXT:    [[MUL21:%.*]] = add i32 [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[ADD1:%.*]] = mul i32 [[MUL21]], [[X:%.*]]
+; CHECK-NEXT:    ret i32 [[ADD1]]
+;
+  %mul1 = mul i32 %x, %y
+  %mul2 = mul nuw i32 %x, %z
+  %add1 = add nuw i32 %mul1, %mul2
+  ret i32 %add1
+}
+
+define i32 @tryFactorization_add_nuw_mul_nuw_mul_var(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @tryFactorization_add_nuw_mul_nuw_mul_var(
+; CHECK-NEXT:    [[MUL21:%.*]] = add i32 [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[ADD1:%.*]] = mul i32 [[MUL21]], [[X:%.*]]
+; CHECK-NEXT:    ret i32 [[ADD1]]
+;
+  %mul1 = mul nuw i32 %x, %y
+  %mul2 = mul i32 %x, %z
+  %add1 = add nuw i32 %mul1, %mul2
+  ret i32 %add1
+}
+
+define i32 @tryFactorization_add_mul_nuw_mul_var(i32 %x, i32 %y, i32 %z) {
+; CHECK-LABEL: @tryFactorization_add_mul_nuw_mul_var(
+; CHECK-NEXT:    [[MUL21:%.*]] = add i32 [[Y:%.*]], [[Z:%.*]]
+; CHECK-NEXT:    [[ADD1:%.*]] = mul i32 [[MUL21]], [[X:%.*]]
+; CHECK-NEXT:    ret i32 [[ADD1]]
+;
+  %mul1 = mul nuw i32 %x, %y
+  %mul2 = mul nuw i32 %x, %z
+  %add1 = add i32 %mul1, %mul2
+  ret i32 %add1
+}