commit d0bcef204038b02271b94b0b40e6213a2e34d1da
author David Majnemer <david.majnemer@gmail.com> Sat Dec 27 19:45:38 2014 +0000
committer David Majnemer <david.majnemer@gmail.com> Sat Dec 27 19:45:38 2014 +0000
tree a6d84a5be34cb843590ddaaa5eba999b258a9407
parent 4eb5c2e089218940cb8b9a8b0d26fed7ba39b89e

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

llvm-svn: 224890

llvm/lib/Target/PowerPC/PPCCTRLoops.cpp

diff --git a/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp b/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
index 5f3b176..167f335 100644
--- a/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
+++ b/llvm/lib/Target/PowerPC/PPCCTRLoops.cpp
@@ -194,6 +194,21 @@
   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 @@
       if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries())
         return true;
     }
+    for (Value *Operand : J->operands())
+      if (memAddrUsesCTR(TM, Operand))
+        return true;
   }
 
   return false;

llvm/test/CodeGen/PowerPC/ctrloops.ll

diff --git a/llvm/test/CodeGen/PowerPC/ctrloops.ll b/llvm/test/CodeGen/PowerPC/ctrloops.ll
index ca00f68..ccab7cb 100644
--- a/llvm/test/CodeGen/PowerPC/ctrloops.ll
+++ b/llvm/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 @@
 ; 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
+}