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PowerPC: CTR shouldn't fire if a TLS call is in the loop

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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
This commit is contained in:
David Majnemer 2014-12-27 19:45:38 +00:00
parent 22376afd76
commit bd64447bf3
2 changed files with 42 additions and 1 deletions
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18
lib/Target/PowerPC/PPCCTRLoops.cpp
View File

@ -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;

25
test/CodeGen/PowerPC/ctrloops.ll
View File

@ -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
}