From bd64447bf33818e565b00fcccedab4844f4c6b6f Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Sat, 27 Dec 2014 19:45:38 +0000
Subject: [PATCH] PowerPC: CTR shouldn't fire if a TLS call is in the loop

Determining the address of a TLS variable results in a function call in
certain TLS models.  This means that a simple ICmpInst might actually
result in invalidating the CTR register.

In such cases, do not attempt to rely on the CTR register for loop
optimization purposes.

This fixes PR22034.

Differential Revision: http://reviews.llvm.org/D6786

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224890 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/PowerPC/PPCCTRLoops.cpp | 18 ++++++++++++++++++
 test/CodeGen/PowerPC/ctrloops.ll   | 25 ++++++++++++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/lib/Target/PowerPC/PPCCTRLoops.cpp b/lib/Target/PowerPC/PPCCTRLoops.cpp
index 5f3b1764173..167f3355eb2 100644
--- a/lib/Target/PowerPC/PPCCTRLoops.cpp
+++ b/lib/Target/PowerPC/PPCCTRLoops.cpp
@@ -194,6 +194,21 @@ static bool isLargeIntegerTy(bool Is32Bit, Type *Ty) {
   return false;
 }
 
+// Determining the address of a TLS variable results in a function call in
+// certain TLS models.
+static bool memAddrUsesCTR(const PPCTargetMachine *TM,
+                           const llvm::Value *MemAddr) {
+  const auto *GV = dyn_cast<GlobalValue>(MemAddr);
+  if (!GV)
+    return false;
+  if (!GV->isThreadLocal())
+    return false;
+  if (!TM)
+    return true;
+  TLSModel::Model Model = TM->getTLSModel(GV);
+  return Model == TLSModel::GeneralDynamic || Model == TLSModel::LocalDynamic;
+}
+
 bool PPCCTRLoops::mightUseCTR(const Triple &TT, BasicBlock *BB) {
   for (BasicBlock::iterator J = BB->begin(), JE = BB->end();
        J != JE; ++J) {
@@ -389,6 +404,9 @@ bool PPCCTRLoops::mightUseCTR(const Triple &TT, BasicBlock *BB) {
       if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries())
         return true;
     }
+    for (Value *Operand : J->operands())
+      if (memAddrUsesCTR(TM, Operand))
+        return true;
   }
 
   return false;
diff --git a/test/CodeGen/PowerPC/ctrloops.ll b/test/CodeGen/PowerPC/ctrloops.ll
index ca00f687aa4..ccab7cb7a0b 100644
--- a/test/CodeGen/PowerPC/ctrloops.ll
+++ b/test/CodeGen/PowerPC/ctrloops.ll
@@ -1,6 +1,6 @@
 target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v128:128:128-n32:64"
 target triple = "powerpc64-unknown-freebsd10.0"
-; RUN: llc < %s -march=ppc64 | FileCheck %s
+; RUN: llc < %s -march=ppc64 -relocation-model=pic | FileCheck %s
 
 @a = common global i32 0, align 4
 
@@ -73,3 +73,26 @@ for.end:                                          ; preds = %for.body, %entry
 ; CHECK-NOT: cmplwi
 ; CHECK: bdnz
 }
+
+@tls_var = external thread_local global i8
+
+define i32 @test4() {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %phi = phi i32 [ %dec, %for.body ], [ undef, %entry ]
+  %load = ptrtoint i8* @tls_var to i32
+  %dec = add i32 %phi, -1
+  %cmp = icmp sgt i32 %phi, 1
+  br i1 %cmp, label %for.body, label %return
+
+return:                                           ; preds = %for.body
+  ret i32 %load
+; CHECK-LABEL: @test4
+; CHECK-NOT: mtctr
+; CHECK: addi {{[0-9]+}}
+; CHECK: cmpwi
+; CHECK-NOT: bdnz
+; CHECK: bgt
+}
-- 
2.34.1