[llvm] r364234 - InstCombine: Preserve nuw when reassociating nuw ops [2/3]

[Matt Arsenault via llvm-commits]

Author: arsenm
Date: Mon Jun 24 14:37:02 2019
New Revision: 364234

URL: http://llvm.org/viewvc/llvm-project?rev=364234&view=rev
Log:
InstCombine: Preserve nuw when reassociating nuw ops [2/3]

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=364234&r1=364233&r2=364234&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstructionCombining.cpp Mon Jun 24 14:37:02 2019
@@ -431,8 +431,14 @@ bool InstCombiner::SimplifyAssociativeOr
           Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode &&
           match(Op0, m_OneUse(m_BinOp(m_Value(A), m_Constant(C1)))) &&
           match(Op1, m_OneUse(m_BinOp(m_Value(B), m_Constant(C2))))) {
-        BinaryOperator *NewBO = BinaryOperator::Create(Opcode, A, B);
-        if (isa<FPMathOperator>(NewBO)) {
+        bool IsNUW = hasNoUnsignedWrap(I) &&
+           hasNoUnsignedWrap(*Op0) &&
+           hasNoUnsignedWrap(*Op1);
+         BinaryOperator *NewBO = (IsNUW && Opcode == Instruction::Add) ?
+           BinaryOperator::CreateNUW(Opcode, A, B) :
+           BinaryOperator::Create(Opcode, A, B);
+
+         if (isa<FPMathOperator>(NewBO)) {
           FastMathFlags Flags = I.getFastMathFlags();
           Flags &= Op0->getFastMathFlags();
           Flags &= Op1->getFastMathFlags();
@@ -445,6 +451,8 @@ bool InstCombiner::SimplifyAssociativeOr
         // Conservatively clear the optional flags, since they may not be
         // preserved by the reassociation.
         ClearSubclassDataAfterReassociation(I);
+        if (IsNUW)
+          I.setHasNoUnsignedWrap(true);
 
         Changed = true;
         continue;

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=364234&r1=364233&r2=364234&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/reassociate-nuw.ll Mon Jun 24 14:37:02 2019
@@ -55,8 +55,8 @@ define i32 @no_reassoc_add_none_nuw(i32
 
 define i32 @reassoc_x2_add_nuw(i32 %x, i32 %y) {
 ; CHECK-LABEL: @reassoc_x2_add_nuw(
-; CHECK-NEXT:    [[ADD1:%.*]] = add i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[ADD2:%.*]] = add i32 [[ADD1]], 12
+; CHECK-NEXT:    [[ADD1:%.*]] = add nuw i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[ADD2:%.*]] = add nuw i32 [[ADD1]], 12
 ; CHECK-NEXT:    ret i32 [[ADD2]]
 ;
   %add0 = add nuw i32 %x, 4
@@ -68,7 +68,7 @@ define i32 @reassoc_x2_add_nuw(i32 %x, i
 define i32 @reassoc_x2_mul_nuw(i32 %x, i32 %y) {
 ; CHECK-LABEL: @reassoc_x2_mul_nuw(
 ; CHECK-NEXT:    [[MUL1:%.*]] = mul i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT:    [[MUL2:%.*]] = mul i32 [[MUL1]], 45
+; CHECK-NEXT:    [[MUL2:%.*]] = mul nuw i32 [[MUL1]], 45
 ; CHECK-NEXT:    ret i32 [[MUL2]]
 ;
   %mul0 = mul nuw i32 %x, 5