aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
Diffstat
-rw-r--r--lib/Target/X86/CMakeLists.txt1
-rw-r--r--lib/Target/X86/X86.h4
-rw-r--r--lib/Target/X86/X86.td9
-rw-r--r--lib/Target/X86/X86PadShortFunction.cpp171
-rw-r--r--lib/Target/X86/X86Subtarget.cpp1
-rw-r--r--lib/Target/X86/X86Subtarget.h5
-rw-r--r--lib/Target/X86/X86TargetMachine.cpp6
-rw-r--r--test/CodeGen/X86/atom-pad-short-functions.ll78
-rw-r--r--test/CodeGen/X86/fast-isel-x86-64.ll4
-rw-r--r--test/CodeGen/X86/ret-mmx.ll2
-rw-r--r--test/CodeGen/X86/select.ll4
11 files changed, 277 insertions, 8 deletions
diff --git a/lib/Target/X86/CMakeLists.txt b/lib/Target/X86/CMakeLists.txt
index 95f1f22e04..d14899d28a 100644
--- a/lib/Target/X86/CMakeLists.txt
+++ b/lib/Target/X86/CMakeLists.txt
@@ -25,6 +25,7 @@ set(sources
X86JITInfo.cpp
X86MCInstLower.cpp
X86MachineFunctionInfo.cpp
+ X86PadShortFunction.cpp
X86RegisterInfo.cpp
X86SelectionDAGInfo.cpp
X86Subtarget.cpp
diff --git a/lib/Target/X86/X86.h b/lib/Target/X86/X86.h
index 2bff7ab15a..1f9919f159 100644
--- a/lib/Target/X86/X86.h
+++ b/lib/Target/X86/X86.h
@@ -66,6 +66,10 @@ FunctionPass *createEmitX86CodeToMemory();
/// \brief Creates an X86-specific Target Transformation Info pass.
ImmutablePass *createX86TargetTransformInfoPass(const X86TargetMachine *TM);
+/// createX86PadShortFunctions - Return a pass that pads short functions
+/// with NOOPs. This will prevent a stall when returning on the Atom.
+FunctionPass *createX86PadShortFunctions();
+
} // End llvm namespace
#endif
diff --git a/lib/Target/X86/X86.td b/lib/Target/X86/X86.td
index b9d8cf7645..3ab2899365 100644
--- a/lib/Target/X86/X86.td
+++ b/lib/Target/X86/X86.td
@@ -123,8 +123,11 @@ def FeatureRTM : SubtargetFeature<"rtm", "HasRTM", "true",
def FeatureLeaForSP : SubtargetFeature<"lea-sp", "UseLeaForSP", "true",
"Use LEA for adjusting the stack pointer">;
def FeatureSlowDivide : SubtargetFeature<"idiv-to-divb",
- "HasSlowDivide", "true",
- "Use small divide for positive values less than 256">;
+ "HasSlowDivide", "true",
+ "Use small divide for positive values less than 256">;
+def FeaturePadShortFunctions : SubtargetFeature<"pad-short-functions",
+ "PadShortFunctions", "true",
+ "Pad short functions">;
//===----------------------------------------------------------------------===//
// X86 processors supported.
@@ -167,7 +170,7 @@ def : Proc<"penryn", [FeatureSSE41, FeatureCMPXCHG16B,
FeatureSlowBTMem]>;
def : AtomProc<"atom", [ProcIntelAtom, FeatureSSSE3, FeatureCMPXCHG16B,
FeatureMOVBE, FeatureSlowBTMem, FeatureLeaForSP,
- FeatureSlowDivide]>;
+ FeatureSlowDivide, FeaturePadShortFunctions]>;
// "Arrandale" along with corei3 and corei5
def : Proc<"corei7", [FeatureSSE42, FeatureCMPXCHG16B,
FeatureSlowBTMem, FeatureFastUAMem,
diff --git a/lib/Target/X86/X86PadShortFunction.cpp b/lib/Target/X86/X86PadShortFunction.cpp
new file mode 100644
index 0000000000..c22872f128
--- /dev/null
+++ b/lib/Target/X86/X86PadShortFunction.cpp
@@ -0,0 +1,171 @@
+//===-------- X86PadShortFunction.cpp - pad short functions -----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the pass which will pad short functions to prevent
+// a stall if a function returns before the return address is ready. This
+// is needed for some Intel Atom processors.
+//
+//===----------------------------------------------------------------------===//
+
+#include <algorithm>
+
+#define DEBUG_TYPE "x86-pad-short-functions"
+#include "X86.h"
+#include "X86InstrInfo.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetInstrInfo.h"
+
+using namespace llvm;
+
+STATISTIC(NumBBsPadded, "Number of basic blocks padded");
+
+namespace {
+ struct PadShortFunc : public MachineFunctionPass {
+ static char ID;
+ PadShortFunc() : MachineFunctionPass(ID)
+ , Threshold(4), TM(0), TII(0) {}
+
+ virtual bool runOnMachineFunction(MachineFunction &MF);
+
+ virtual const char *getPassName() const {
+ return "X86 Atom pad short functions";
+ }
+
+ private:
+ void findReturns(MachineBasicBlock *MBB,
+ unsigned int Cycles = 0);
+
+ bool cyclesUntilReturn(MachineBasicBlock *MBB,
+ unsigned int &Cycles,
+ MachineBasicBlock::iterator *Location = 0);
+
+ void addPadding(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &MBBI,
+ unsigned int NOOPsToAdd);
+
+ const unsigned int Threshold;
+ DenseMap<MachineBasicBlock*, unsigned int> ReturnBBs;
+
+ const TargetMachine *TM;
+ const TargetInstrInfo *TII;
+ };
+
+ char PadShortFunc::ID = 0;
+}
+
+FunctionPass *llvm::createX86PadShortFunctions() {
+ return new PadShortFunc();
+}
+
+/// runOnMachineFunction - Loop over all of the basic blocks, inserting
+/// NOOP instructions before early exits.
+bool PadShortFunc::runOnMachineFunction(MachineFunction &MF) {
+ bool OptForSize = MF.getFunction()->getAttributes().
+ hasAttribute(AttributeSet::FunctionIndex, Attribute::OptimizeForSize);
+
+ if (OptForSize)
+ return false;
+
+ TM = &MF.getTarget();
+ TII = TM->getInstrInfo();
+
+ // Search through basic blocks and mark the ones that have early returns
+ ReturnBBs.clear();
+ findReturns(MF.begin());
+
+ bool MadeChange = false;
+
+ MachineBasicBlock::iterator ReturnLoc;
+ MachineBasicBlock *MBB;
+ unsigned int Cycles = 0;
+ unsigned int BBCycles;
+
+ // Pad the identified basic blocks with NOOPs
+ for (DenseMap<MachineBasicBlock*, unsigned int>::iterator I = ReturnBBs.begin();
+ I != ReturnBBs.end(); ++I) {
+ MBB = I->first;
+ Cycles = I->second;
+
+ if (Cycles < Threshold) {
+ if (!cyclesUntilReturn(MBB, BBCycles, &ReturnLoc))
+ continue;
+
+ addPadding(MBB, ReturnLoc, Threshold - Cycles);
+ NumBBsPadded++;
+ MadeChange = true;
+ }
+ }
+
+ return MadeChange;
+}
+
+/// findReturn - Starting at MBB, follow control flow and add all
+/// basic blocks that contain a return to ReturnBBs.
+void PadShortFunc::findReturns(MachineBasicBlock *MBB, unsigned int Cycles) {
+ // If this BB has a return, note how many cycles it takes to get there.
+ bool hasReturn = cyclesUntilReturn(MBB, Cycles);
+ if (Cycles >= Threshold)
+ return;
+
+ if (hasReturn) {
+ ReturnBBs[MBB] = std::max(ReturnBBs[MBB], Cycles);
+ return;
+ }
+
+ // Follow branches in BB and look for returns
+ for (MachineBasicBlock::succ_iterator I = MBB->succ_begin();
+ I != MBB->succ_end(); ++I) {
+ findReturns(*I, Cycles);
+ }
+}
+
+/// cyclesUntilReturn - if the MBB has a return instruction, set Location
+/// to the instruction and return true. Return false otherwise.
+/// Cycles will be incremented by the number of cycles taken to reach the
+/// return or the end of the BB, whichever occurs first.
+bool PadShortFunc::cyclesUntilReturn(MachineBasicBlock *MBB,
+ unsigned int &Cycles,
+ MachineBasicBlock::iterator *Location) {
+ for (MachineBasicBlock::iterator MBBI = MBB->begin();
+ MBBI != MBB->end(); ++MBBI) {
+ MachineInstr *MI = MBBI;
+ // Mark basic blocks with a return instruction. Calls to other
+ // functions do not count because the called function will be padded,
+ // if necessary.
+ if (MI->isReturn() && !MI->isCall()) {
+ if (Location)
+ *Location = MBBI;
+ return true;
+ }
+
+ Cycles += TII->getInstrLatency(TM->getInstrItineraryData(), MI);
+ }
+
+ return false;
+}
+
+/// addPadding - Add the given number of NOOP instructions to the function
+/// just prior to the return at MBBI
+void PadShortFunc::addPadding(MachineBasicBlock *MBB,
+ MachineBasicBlock::iterator &MBBI,
+ unsigned int NOOPsToAdd) {
+ DebugLoc DL = MBBI->getDebugLoc();
+
+ while (NOOPsToAdd-- > 0) {
+ BuildMI(*MBB, MBBI, DL, TII->get(X86::NOOP));
+ BuildMI(*MBB, MBBI, DL, TII->get(X86::NOOP));
+ }
+}
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index d493b78752..53c28f4fce 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -350,6 +350,7 @@ X86Subtarget::X86Subtarget(const std::string &TT, const std::string &CPU,
, UseLeaForSP(false)
, HasSlowDivide(false)
, PostRAScheduler(false)
+ , PadShortFunctions(false)
, stackAlignment(4)
// FIXME: this is a known good value for Yonah. How about others?
, MaxInlineSizeThreshold(128)
diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index 44f38a1a91..080f4cfeca 100644
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -146,6 +146,10 @@ protected:
/// PostRAScheduler - True if using post-register-allocation scheduler.
bool PostRAScheduler;
+ /// PadShortFunctions - True if the short functions should be padded to prevent
+ /// a stall when returning too early.
+ bool PadShortFunctions;
+
/// stackAlignment - The minimum alignment known to hold of the stack frame on
/// entry to the function and which must be maintained by every function.
unsigned stackAlignment;
@@ -231,6 +235,7 @@ public:
bool hasCmpxchg16b() const { return HasCmpxchg16b; }
bool useLeaForSP() const { return UseLeaForSP; }
bool hasSlowDivide() const { return HasSlowDivide; }
+ bool padShortFunctions() const { return PadShortFunctions; }
bool isAtom() const { return X86ProcFamily == IntelAtom; }
diff --git a/lib/Target/X86/X86TargetMachine.cpp b/lib/Target/X86/X86TargetMachine.cpp
index 847e06b960..706e64a09f 100644
--- a/lib/Target/X86/X86TargetMachine.cpp
+++ b/lib/Target/X86/X86TargetMachine.cpp
@@ -202,6 +202,12 @@ bool X86PassConfig::addPreEmitPass() {
ShouldPrint = true;
}
+ if (getOptLevel() != CodeGenOpt::None &&
+ getX86Subtarget().padShortFunctions()) {
+ addPass(createX86PadShortFunctions());
+ ShouldPrint = true;
+ }
+
return ShouldPrint;
}
diff --git a/test/CodeGen/X86/atom-pad-short-functions.ll b/test/CodeGen/X86/atom-pad-short-functions.ll
new file mode 100644
index 0000000000..54af17d4c4
--- /dev/null
+++ b/test/CodeGen/X86/atom-pad-short-functions.ll
@@ -0,0 +1,78 @@
+; RUN: llc < %s -O1 -mcpu=atom -mtriple=i686-linux | FileCheck %s
+
+declare void @external_function(...)
+
+define i32 @test_return_val(i32 %a) nounwind {
+; CHECK: test_return_val
+; CHECK: movl
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: ret
+ ret i32 %a
+}
+
+define i32 @test_optsize(i32 %a) nounwind optsize {
+; CHECK: test_optsize
+; CHECK: movl
+; CHECK-NEXT: ret
+ ret i32 %a
+}
+
+define i32 @test_add(i32 %a, i32 %b) nounwind {
+; CHECK: test_add
+; CHECK: addl
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: ret
+ %result = add i32 %a, %b
+ ret i32 %result
+}
+
+define i32 @test_multiple_ret(i32 %a, i32 %b, i1 %c) nounwind {
+; CHECK: @test_multiple_ret
+; CHECK: je
+
+; CHECK: nop
+; CHECK: nop
+; CHECK: ret
+
+; CHECK: nop
+; CHECK: nop
+; CHECK: ret
+
+ br i1 %c, label %bb1, label %bb2
+
+bb1:
+ ret i32 %a
+
+bb2:
+ ret i32 %b
+}
+
+define void @test_call_others(i32 %x) nounwind
+{
+; CHECK: test_call_others
+; CHECK: je
+ %tobool = icmp eq i32 %x, 0
+ br i1 %tobool, label %if.end, label %true.case
+
+; CHECK: jmp external_function
+true.case:
+ tail call void bitcast (void (...)* @external_function to void ()*)() nounwind
+ br label %if.end
+
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: nop
+; CHECK: ret
+if.end:
+ ret void
+
+}
diff --git a/test/CodeGen/X86/fast-isel-x86-64.ll b/test/CodeGen/X86/fast-isel-x86-64.ll
index cdfaf7f4c1..ad1520ef81 100644
--- a/test/CodeGen/X86/fast-isel-x86-64.ll
+++ b/test/CodeGen/X86/fast-isel-x86-64.ll
@@ -1,5 +1,5 @@
-; RUN: llc < %s -mattr=-avx -fast-isel -O0 -regalloc=fast -asm-verbose=0 -fast-isel-abort | FileCheck %s
-; RUN: llc < %s -mattr=+avx -fast-isel -O0 -regalloc=fast -asm-verbose=0 -fast-isel-abort | FileCheck %s --check-prefix=AVX
+; RUN: llc < %s -mattr=-avx -fast-isel -mcpu=core2 -O0 -regalloc=fast -asm-verbose=0 -fast-isel-abort | FileCheck %s
+; RUN: llc < %s -mattr=+avx -fast-isel -mcpu=core2 -O0 -regalloc=fast -asm-verbose=0 -fast-isel-abort | FileCheck %s --check-prefix=AVX
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-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.0.0"
diff --git a/test/CodeGen/X86/ret-mmx.ll b/test/CodeGen/X86/ret-mmx.ll
index 865e147a4a..778e4722cd 100644
--- a/test/CodeGen/X86/ret-mmx.ll
+++ b/test/CodeGen/X86/ret-mmx.ll
@@ -1,4 +1,4 @@
-; RUN: llc < %s -mtriple=x86_64-apple-darwin11 -mattr=+mmx,+sse2 | FileCheck %s
+; RUN: llc < %s -mtriple=x86_64-apple-darwin11 -mcpu=core2 -mattr=+mmx,+sse2 | FileCheck %s
; rdar://6602459
@g_v1di = external global <1 x i64>
diff --git a/test/CodeGen/X86/select.ll b/test/CodeGen/X86/select.ll
index 3bec3acdbf..09ca07b31a 100644
--- a/test/CodeGen/X86/select.ll
+++ b/test/CodeGen/X86/select.ll
@@ -282,7 +282,7 @@ define i32 @test13(i32 %a, i32 %b) nounwind {
; ATOM: test13:
; ATOM: cmpl
; ATOM-NEXT: sbbl
-; ATOM-NEXT: ret
+; ATOM: ret
}
define i32 @test14(i32 %a, i32 %b) nounwind {
@@ -299,7 +299,7 @@ define i32 @test14(i32 %a, i32 %b) nounwind {
; ATOM: cmpl
; ATOM-NEXT: sbbl
; ATOM-NEXT: notl
-; ATOM-NEXT: ret
+; ATOM: ret
}
; rdar://10961709
generated by cgit v1.2.3-18-g5258 (git 2.32.0) at 2024-11-22 03:02:37 +0000