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Add a TargetOption for disabling tail calls.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@148442 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Nick Lewycky 2012-01-19 00:34:10 +00:00
parent 9b159710eb
commit 22de16dc75
4 changed files with 57 additions and 3 deletions
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9
include/llvm/Target/TargetOptions.h
View File

@ -43,8 +43,9 @@ namespace llvm {
NoNaNsFPMath(false), HonorSignDependentRoundingFPMathOption(false),
UseSoftFloat(false), NoZerosInBSS(false), JITExceptionHandling(false),
JITEmitDebugInfo(false), JITEmitDebugInfoToDisk(false),
GuaranteedTailCallOpt(false), StackAlignmentOverride(0),
RealignStack(true), DisableJumpTables(false), EnableFastISel(false),
GuaranteedTailCallOpt(false), DisableTailCalls(false),
StackAlignmentOverride(0), RealignStack(true),
DisableJumpTables(false), EnableFastISel(false),
EnableSegmentedStacks(false), TrapFuncName(""),
FloatABIType(FloatABI::Default)
{}
@ -147,6 +148,10 @@ namespace llvm {
/// as their parent function, etc.), using an alternate ABI if necessary.
unsigned GuaranteedTailCallOpt : 1;
/// DisableTailCalls - This flag controls whether we will use tail calls.
/// Disabling them may be useful to maintain a correct call stack.
unsigned DisableTailCalls : 1;
/// StackAlignmentOverride - Override default stack alignment for target.
unsigned StackAlignmentOverride;

5
lib/Target/X86/X86ISelLowering.cpp
View File

@ -1732,7 +1732,7 @@ static bool IsTailCallConvention(CallingConv::ID CC) {
}
bool X86TargetLowering::mayBeEmittedAsTailCall(CallInst *CI) const {
if (!CI->isTailCall())
if (!CI->isTailCall() || getTargetMachine().Options.DisableTailCalls)
return false;
CallSite CS(CI);
@ -2133,6 +2133,9 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
bool IsStructRet = CallIsStructReturn(Outs);
bool IsSibcall = false;
if (MF.getTarget().Options.DisableTailCalls)
isTailCall = false;
if (isTailCall) {
// Check if it's really possible to do a tail call.
isTailCall = IsEligibleForTailCallOptimization(Callee, CallConv,

40
test/CodeGen/X86/tailcall-disable.ll Normal file
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@ -0,0 +1,40 @@
; RUN: llc -disable-tail-calls < %s | FileCheck --check-prefix=CALL %s
; RUN: llc < %s | FileCheck --check-prefix=JMP %s
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-S128"
target triple = "x86_64-unknown-linux-gnu"
define i32 @helper() nounwind {
entry:
ret i32 7
}
define i32 @test1() nounwind {
entry:
%call = tail call i32 @helper()
ret i32 %call
}
;CALL: test1:
;CALL-NOT: ret
;CALL: callq helper
;CALL: ret
;JMP: test1:
;JMP-NOT: ret
;JMP: jmp helper # TAILCALL
define i32 @test2() nounwind {
entry:
%call = tail call i32 @test2()
ret i32 %call
}
;CALL: test2:
;CALL-NOT: ret
;CALL: callq test2
;CALL: ret
;JMP: test2:
;JMP-NOT: ret
;JMP: jmp test2 # TAILCALL

6
tools/llc/llc.cpp
View File

@ -237,6 +237,11 @@ EnableGuaranteedTailCallOpt("tailcallopt",
cl::desc("Turn fastcc calls into tail calls by (potentially) changing ABI."),
cl::init(false));
static cl::opt<bool>
DisableTailCalls("disable-tail-calls",
cl::desc("Never emit tail calls"),
cl::init(false));
static cl::opt<unsigned>
OverrideStackAlignment("stack-alignment",
cl::desc("Override default stack alignment"),
@ -462,6 +467,7 @@ int main(int argc, char **argv) {
Options.JITEmitDebugInfo = EmitJitDebugInfo;
Options.JITEmitDebugInfoToDisk = EmitJitDebugInfoToDisk;
Options.GuaranteedTailCallOpt = EnableGuaranteedTailCallOpt;
Options.DisableTailCalls = DisableTailCalls;
Options.StackAlignmentOverride = OverrideStackAlignment;
Options.RealignStack = EnableRealignStack;
Options.DisableJumpTables = DisableSwitchTables;