[llvm] r224890 - PowerPC: CTR shouldn't fire if a TLS call is in the loop

[David Majnemer]

Author: majnemer
Date: Sat Dec 27 13:45:38 2014
New Revision: 224890

URL: http://llvm.org/viewvc/llvm-project?rev=224890&view=rev
Log:
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

Modified:
    llvm/trunk/lib/Target/PowerPC/PPCCTRLoops.cpp
    llvm/trunk/test/CodeGen/PowerPC/ctrloops.ll

Modified: llvm/trunk/lib/Target/PowerPC/PPCCTRLoops.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCCTRLoops.cpp?rev=224890&r1=224889&r2=224890&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCCTRLoops.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCCTRLoops.cpp Sat Dec 27 13:45:38 2014
@@ -194,6 +194,21 @@ static bool isLargeIntegerTy(bool Is32Bi
   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 Trip
       if (SI->getNumCases() + 1 >= (unsigned)TLI->getMinimumJumpTableEntries())
         return true;
     }
+    for (Value *Operand : J->operands())
+      if (memAddrUsesCTR(TM, Operand))
+        return true;
   }
 
   return false;

Modified: llvm/trunk/test/CodeGen/PowerPC/ctrloops.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/ctrloops.ll?rev=224890&r1=224889&r2=224890&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/ctrloops.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/ctrloops.ll Sat Dec 27 13:45:38 2014
@@ -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:
 ; CHECK-NOT: cmplwi
 ; CHECK: bdnz
 }
+
+ at 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
+}