From 630077ef558317ac85bfc266737040eaecd0bcb0 Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Fri, 20 Nov 2015 08:16:13 +0000
Subject: [PATCH] Fix a pair of issues that caused an infinite loop in
 reassociate.

Terrifyingly, one of them is a mishandling of floating point vectors
in Constant::isZero().  How exactly this issue survived this long
is beyond me.

llvm-svn: 253655
---
 llvm/lib/IR/Constants.cpp                   |  6 ++++++
 llvm/lib/Transforms/Scalar/Reassociate.cpp  |  2 +-
 llvm/test/Transforms/Reassociate/fp-expr.ll | 20 ++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 llvm/test/Transforms/Reassociate/fp-expr.ll

diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index 550d9a89a65e..b237c913dcf1 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -68,6 +68,12 @@ bool Constant::isZeroValue() const {
   if (const ConstantFP *CFP = dyn_cast<ConstantFP>(this))
     return CFP->isZero();
 
+  // Equivalent for a vector of -0.0's.
+  if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
+    if (ConstantFP *SplatCFP = dyn_cast_or_null<ConstantFP>(CV->getSplatValue()))
+      if (SplatCFP && SplatCFP->isZero())
+        return true;
+
   // Otherwise, just use +0.0.
   return isNullValue();
 }
diff --git a/llvm/lib/Transforms/Scalar/Reassociate.cpp b/llvm/lib/Transforms/Scalar/Reassociate.cpp
index 82c79e7d9199..fa2f7d995c69 100644
--- a/llvm/lib/Transforms/Scalar/Reassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/Reassociate.cpp
@@ -2064,7 +2064,7 @@ void Reassociate::OptimizeInst(Instruction *I) {
     return;
 
   // Don't optimize floating point instructions that don't have unsafe algebra.
-  if (I->getType()->isFloatingPointTy() && !I->hasUnsafeAlgebra())
+  if (I->getType()->isFPOrFPVectorTy() && !I->hasUnsafeAlgebra())
     return;
 
   // Do not reassociate boolean (i1) expressions.  We want to preserve the
diff --git a/llvm/test/Transforms/Reassociate/fp-expr.ll b/llvm/test/Transforms/Reassociate/fp-expr.ll
new file mode 100644
index 000000000000..ee9270698124
--- /dev/null
+++ b/llvm/test/Transforms/Reassociate/fp-expr.ll
@@ -0,0 +1,20 @@
+; RUN: opt -S -reassociate < %s | FileCheck %s
+
+define void @test1() {
+; CHECK-LABEL: @test1
+; CHECK: call
+; CHECK: fsub
+; CHECK: fadd
+  %tmp = tail call <4 x float> @blam()
+  %tmp23 = fsub fast <4 x float> undef, %tmp
+  %tmp24 = fadd fast <4 x float> %tmp23, undef
+  tail call void @wombat(<4 x float> %tmp24)
+  ret void
+}
+
+; Function Attrs: optsize
+declare <4 x float> @blam()
+
+; Function Attrs: optsize
+declare void @wombat(<4 x float>)
+