From 5195b71941b49b3be7915cf4a52c951ac72e0a83 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Wed, 2 Feb 2011 02:05:46 +0000
Subject: [PATCH] Conservatively, clear optional flags, such as nsw, when
 performing reassociation. No testcase, because I wasn't able to create a
 testcase which actually demonstrates a problem.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124713 91177308-0d34-0410-b5e6-96231b3b80d8
---
 .../InstCombine/InstructionCombining.cpp          | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index 2d5773a31fc..7208ad0c7cc 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -157,6 +157,9 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           // It simplifies to V.  Form "A op V".
           I.setOperand(0, A);
           I.setOperand(1, V);
+          // Conservatively clear the optional flags, since they may not be
+          // preserved by the reassociation.
+          I.clearSubclassOptionalData();
           Changed = true;
           ++NumReassoc;
           continue;
@@ -174,6 +177,9 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           // It simplifies to V.  Form "V op C".
           I.setOperand(0, V);
           I.setOperand(1, C);
+          // Conservatively clear the optional flags, since they may not be
+          // preserved by the reassociation.
+          I.clearSubclassOptionalData();
           Changed = true;
           ++NumReassoc;
           continue;
@@ -193,6 +199,9 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           // It simplifies to V.  Form "V op B".
           I.setOperand(0, V);
           I.setOperand(1, B);
+          // Conservatively clear the optional flags, since they may not be
+          // preserved by the reassociation.
+          I.clearSubclassOptionalData();
           Changed = true;
           ++NumReassoc;
           continue;
@@ -210,6 +219,9 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
           // It simplifies to V.  Form "B op V".
           I.setOperand(0, B);
           I.setOperand(1, V);
+          // Conservatively clear the optional flags, since they may not be
+          // preserved by the reassociation.
+          I.clearSubclassOptionalData();
           Changed = true;
           ++NumReassoc;
           continue;
@@ -234,6 +246,9 @@ bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) {
         Worklist.Add(New);
         I.setOperand(0, New);
         I.setOperand(1, Folded);
+        // Conservatively clear the optional flags, since they may not be
+        // preserved by the reassociation.
+        I.clearSubclassOptionalData();
         Changed = true;
         continue;
       }